Electrical and Energy

The Guidelines for Transformator Application Designs

2012-02-14T11:14:00.001+07:00

The time you spend in selecting a transformer seems to be in direct proportion to the size of the unit. All too often, small transformers are selected with just a cursory look at the connected loads, and frequently a decision is made to choose one with the next larger kVA rating than the anticipated load. Conversely, large transformers, such as those used in electric utility applications, are closely evaluated because they represent large investments.

Most transformers used in commercial and industrial facilities fall in the middle ground, and they usually have ratings between 250kVA and 1000kVA. On larger projects, they can go up to 10MVA. Because these transformers represent the majority, you should evaluate them carefully before choosing a unit for a specific project and/or application.

Selection Process

There are three main parameters in choosing a transformer:

* That it has enough capacity to handle the expected loads (as well as a certain amount of overload);

* That consideration be given to possibly increasing the capacity to handle potential load growth; and

* That the funds allocated for its purchase be based on a certain life expectancy (with consideration to an optimal decision on initial, operational, and installation costs.)

Both capacity and cost relate to a number of factors that you should evaluate. These include:

* Application of the unit;

* Choice of insulation type (liquid-filled or dry type);

* Choice of winding material (copper or aluminum);

* Possible use of low-loss core material;

* Regulation (voltage stability);

* Life expectancy;

* Any overloading requirements;

* Basic insulation level (BIL);

* Temperature considerations;

* Losses (both no-load and operating losses);

* Any non-linear load demand;

* Shielding; and

* Accessories.

Application of The unit

The type of load and the transformer's placement are two key considerations that must be understood. For example, if the unit will be used for heavy welding service, such as in an automotive plant, very rigid construction will be called for because the coils will experience very frequent short-circuit-type loads; thus, good short-term overload capability may be required.

You'll find that sizing a transformer for a particular application with regard to the unit's life expectancy requires a good understanding of its insulation characteristics and the winding temperature due to loading. This, in turn, requires a careful analysis of the load profile (covering amplitude, duration, and the extent of linear and non-linear loads).

The standard parameters for transformers operating under normal conditions include:

* Nominal values of input voltage and frequency;

* Approximately sinusoidal input voltage;

* Load current with a harmonic factor not exceeding 0.05 p.u.;

* Installation at an altitude of less than 1000 m (3300 ft);

* No damaging fumes, dust, vapors, etc. in installed environment;

* An ambient temperature that does not exceed 30 [degrees] C as a daily average or 40 [degrees] C at any time, and which does not fall below - 20 [degrees] C; and

* Overloads within acceptable levels of ANSI/IEEE loading guidelines (dry or liquid).

If some of the above conditions can't be met in a particular application, then you should work closely with the manufacturer so that the selected transformer's operating characteristics and/or size will compensate for the particular situation. For example, if the ambient temperature will exceed standard conditions or if the unit will be installed at a high elevation, then an appropriate solution might be to specify a transformer that's rated higher than what the load requires, in effect under utilizing the unit to compensate for the local conditions.

Choice of Liquid-Filled or Dry Type

Information on the pros and cons of the available types of transformers frequently varies depending upon which manufacturer you're talking to and what literature you're reading. Nevertheless, there are certain performance and application characteristics that are almost universally accepted.

Basically, there are two distinct types of transformers: Liquid insulated and cooled (liquid-filled type) and nonliquid insulated, air or air/gas cooled (dry type). Also, there are subcategories of each main type.

Liquid-filled. For liquid-filled transformers, the cooling medium can be conventional mineral oil. There are also wet-type transformers using less flammable liquids, such as high fire point hydrocarbons and silicones.

Liquid-filled transformers are normally more efficient than dry-types, and they usually have a longer life expectancy. Also, liquid is a more efficient cooling medium in reducing hot spot temperatures in the coils. In addition, liquid-filled units have a better overload capability.

There are some drawbacks, however. For example, fire prevention is more important with liquid-type units because of the use of a liquid cooling medium that may catch fire. (Dry-type transformers can catch fire, too.) It's even possible for an improperly protected wet-type transformer to explode. And, depending on the application, liquid-filled transformers may require a containment trough for protection against possible leaks of the fluid.

Because of the above reasons, and because of the ratings, indoor-installed distribution transformers of 600V and below usually are dry-types.

Arguably, when choosing transformers, the changeover point between dry-types and wet-types is between 500kVA to about 2.5MVA, with dry-types used for the lower ratings and wet-types for the higher ratings. Important factors when choosing what type to use include where the transformer will be installed, such as inside an office building or outside, servicing an industrial load. Dry-type transformers with ratings exceeding 5MVA are available, but the vast majority of the higher-capacity transformers are liquid-filled. For outdoor applications, wet-type transformers are the predominate choice.

Dry-type. Dry-type transformers come in enclosures that have louvers or are sealed. Here, subcategories include different methods of insulation such as conventional varnish, vacuum pressure impregnated (VPI) varnish, epoxy resin, or cast resin insulation systems.

Liquid-Filled Insulation Systems

The insulation system for liquid-filled distribution transformers is typically composed of enameled wire, cellulose paper impregnated with a dielectric liquid, and the liquid itself. The dielectric grade paper most often used is derived from sulfate (kraft) wood pulp from softwoods. With the introduction of dicydianamid to the paper making process, the standard temperature winding rise is now 65 [degrees] C.

The ambient temperature base in the United States is a 30 [degrees] C average over a 24-hr period with a 40 [degrees] C maximum. The present allowable hot spot temperature (the difference between the average winding temperature rise and the hottest spot in the windings) is 15 [degrees] C. Thus, the permitted operating hot spot temperature, based on an average ambient temperature of 30 [degrees] C, is 110 [degrees] C.

New synthetic insulating materials are leading to even higher permitted hot spots. These materials include polyester, fiber glass, and more commonly, aramid paper. "Aramid paper" is a term applied generically for wholly aromatic polymide paper. To keep costs reasonable while still achieving gains in acceptable hot spot temperature limits, both aramid and thermally upgraded kraft paper are used together in a hybrid insulation system. As of this writing, new type liquid-filled transformers, called High Temperature Transformers (HTTs) are being built using this technology. The temperature rise of HTTs is an average winding rise of 115 [degrees] C over a 30 [degrees] C average ambient. Factoring in the temperature difference (20 [degrees] C) between the average winding temperature (145 [degrees] C) and the hot spot temperature, the maximum temperature (165 [degrees] C) will be at a level that is higher than the fire point of conventional transformer oil (mineral oil). For this reason, it's recommended that fire-resistant fluids be used for HTTs.

The process of proper impregnation of the paper with a liquid is a standard manufacturing operation. The core/coil assembly is mounted in the tank, lead assemblies attached, and the filling process begins. A partial vacuum is produced while the secondary leads circulate current to heat the coils and drive out any excess moisture. Later, while still under vacuum, heated degassified and filtered dielectric liquid is introduced. After filling and additional vacuum time, the tank cover is sealed in place. The head space between the liquid surface and the tank cover, which allows for the expansion and contraction due to thermal cycling, can be specified to be dry nitrogen gas in larger units.

Environmental Concerns

For liquid-filled transformers containing more than 660 gal, the Environmental Protection Agency (EPA) requires some type of containment be used to control possible leaks of the liquid. Environmentally unfriendly fluids, such as polychlorinated biphenyls (PCBs) and chlorofluorocarbons (CFCs), have been banned or are severely restricted, replaced for the most part by nontoxic, nonbioaccumulating, and nonozone depleting fluids, such as fire-resistant silicones and fire-resistant hydrocarbons. These fluids are not covered by the Resource Conservation and Recovery Act (RCRA); however, they are covered by the Clean Water Act (CWA).

Some transformer liquids (known as nonflammable-type fluids) are covered under both the RCRA and the CWA, and certain requirements may be called for regarding special handling, spill reporting, disposal procedures, and record keeping. These fluids also require provisions for special transformer venting. As such, the above factors can have an effect on installation costs, long-term operating costs, and maintenance procedures.

Liquid Dielectric Selection Factors

The selection of which liquid dielectric coolant to use is driven primarily by economics and codes. Conventional mineral oil is most often specified as it is very economical and, unless it's subject to unusual service, maintains acceptable performance for decades.

As it's possible that a high-energy arc can occur in a transformer, fire safety becomes an important issue. When conventional mineral oil is restricted (usually due to fire code requirements), less-flammable fluids often are used. The most popular are fire-resistant hydrocarbons (also known as high-molecular weight hydrocarbons) and 50 cSt (a viscosity measurement unit) silicone fluids. Other fluids include high fire point polyol esters and polyalpha olefins. In addition to safety considerations, you should also evaluate performance factors for liquid-filled transformers in regard to dielectric strength and heat transfer capabilities of the fluid. The fire resistant hydrocarbon fluids have been widely used in power-class transformations though 60MVA and have over a 500kV BIL.

At one time, askarel fluid, a generic term for a group of certain fire-resistant electrical insulating liquids, including often used PCBs, represented the standard for fire safety in liquid dielectrics. But, PCBs were banned because of toxicity and environmental concerns.

Cost Coil Insulation Systems

Dry-type transformers can have their windings insulated various ways. A basic method is to preheat the conductor coils and then, when heated, dip them in varnish at an elevated temperature. The coils are then baked to cure the varnish. This process is an open-wound method and helps ensure penetration of the varnish. Cooling ducts in the windings provide an efficient and economical way to remove the heat produced by the electrical losses of the transformer by allowing air to flow through the duct openings. This dry-type insulation system operates satisfactorily in most ambient conditions found in commercial buildings and many industrial facilities.

When greater mechanical strength of the windings and increased resistance to corona (electrical discharges caused by the field intensity exceeding the dielectric strength of the insulation) is called for, VPI of the varnish forces the insulation (varnish) into the coils by using both vacuum and pressure. Sometimes, for additional protection against the environment (when the ambient air can be somewhat harmful), the end coils are also sealed with an epoxy resin mixture.

A cast coil insulation system, another version of the dry-type transformer, is used when additional coil strength and protection are advisable. This type of insulation is used for transformers located in harsh environments such as cement and chemical plants and outdoor installations where moisture, salt spray, corrosive fumes, dust, and metal particles can destroy other types of dry-type transformers. These cast coil units are better able to withstand heavy power surges, such as frequent but brief overloads experienced by transformers serving transit systems and various industrial machinery. Cast coil units also are being used where previously only liquid-filled units were available for harsh environments: They can have the same high levels of BIL while still providing ample protection of the coils and the leads going to the terminals.

Unlike open-wound or VPI transformers, cast coil units have their windings completely cast in solid epoxy. The coils are placed into molds and cast, usually under vacuum. The epoxy is a special type that keeps the coils protected from corrosive atmospheres and moisture as well as keeping the coils secure from the high mechanical forces associated with power surges and short circuits. Mineral fillers and glass fibers are added to the pure epoxy to give it greater strength. Flexibilizers are also added to improve its ability to expand and contract with the coil conductors for proper operation of the transformer under various load conditions.

Different manufacturers use different epoxy filling material and in different amounts. Important factors that manufacturers must consider when choosing filler material and the proportion to use include:

* Temperature rating of the transformer;

* Mechanical strength of the coils;

* Dielectric strength of the insulation;

* Expansion rate of the conductors under various loadings; and

* Resistance to thermal shock of the insulation system.

Cast coil transformers consist of separately wound and cast high- and low-voltage coils. During manufacture, the high voltage coil winding wires are placed in a certain pattern using preinsulated wire. The completely wound coil is then placed in a mold designed to form a heavy coating of epoxy around the coil. After vacuum filling of the epoxy, the mold is placed in an oven for a number of hours to allow the epoxy to cure and achieve full hardness and strength.

There are two types of low-voltage windings available, both of which provide protection from hostile environments. One type is vacuum cast like the high-voltage winding. The other type uses a "nonvacuum" technique of epoxy application to achieve strength. Sheet insulation, such as Nomex or fiberglass, is impregnated with uncured epoxy, then interleaved on the heavy low-voltage conductors to literally "wind-in" the epoxy. During oven curing of the low-voltage coil, the epoxy flows onto the conductor and cures into a solid cylinder of great strength. These "non-vacuum" coils are then fully sealed by pouring epoxy into the "margins" or ends of the windings. Both procedures provide good protection from hostile environments.

Because of the additional materials and procedures associated with manufacturing cast coil transformers, they cost more. However, cast coil transformers are designed to operate with lower losses, require less maintenance than regular types, and effectively operate in environments that may cause early failure with conventional dry-types. Also, cast coil transformers, if operated properly, will normally have a longer life expectancy than other dry-type transformers.

Choice of Winding Material

A transformer's coils can be wound with either copper or aluminum conductors. For equivalent electrical and mechanical performance, aluminum-wound transformers usually cost less than copper-wound units. Because copper is a better conductor, a copper-wound transformer can be at times slightly smaller than its aluminum counterpart, for transformers with equivalent electrical ratings, because the copper conductor windings will be smaller. However, most manufacturers supply aluminum and copper transformers in the same enclosure size.

Aluminum-wound transformers are by far the majority choice in the United States. With both materials, the winding process and the application of insulation are the same. Connections to the terminals are welded or brazed. Coils made of copper wires have slightly higher mechanical strength.

You should determine the transformer manufacturer's experience in building its products and that the firm has a proven record in using both types of conductors. This is especially true of manufacturers of dry-type units.

Use of Low-Loss Core Material

Choice of metal is critical for transformer cores, and it's important that good quality magnetic steel be used. There are many grades of steel that can be used for a transformer core. Each grade has an effect on efficiency on a per-pound basis. The choice depends on how you evaluate nonload losses and total owning costs.

Almost all transformer manufacturers today use steel in their cores that provides low losses due to the effects of magnetic hysteresis and eddy currents. To achieve these objectives, high permeability, cold-rolled, grain-oriented, silicon steel is almost always used. Construction of the core utilizes step lap mitered joints and the laminations are carefully stacked.

Amorphous Cores

A new type of liquid-filled transformer introduced commercially in 1986 uses ultra low-loss cores made from amorphous metal; the core losses are between 60% to 70% lower than those for transformers using silicon steel. To date, these transformers have been designed for distribution operation primarily by electric utilities and use wound-cut cores of amorphous metal. Their ratings range from 10kVA through 2500kVA. The reason utilities purchase them, even though they are more expensive than silicon steel core transformers, is because of their high efficiency. U.S. utilities placed more than 400,000 amorphous steel core transformers in operation through 1995. The use of amorphous core liquid-filled transformers is now being expanded for use in power applications for industrial and commercial installations. This is especially true in other countries such as Japan.

Amorphous metal is a new class of material having no crystalline formation. Conventional metals possess crystalline structures in which the atoms form an orderly, repeated, three-dimensional array. Amorphous metals are characterized by a random arrangement of their atoms (because the atomic structure resembles that of glass, the material is sometimes referred to as glassy metal). This atomic structure, along with the difference in the composition and thickness of the metal, accounts for the very low hysteresis and eddy current losses in the new material.

Cost and manufacturing technique are the major obstacles for bringing to the market a broad assortment of amorphous core transformers. The price of these units typically ranges from 15% to 40% higher than that of silicon steel core transformers. To a degree, the price differential is dependent upon which grade of silicon steel the comparison is being made. (The more energy efficient the grade of steel used in the transformer core, the higher the price of the steel.)

At present, amorphous cores are not being applied in dry-type transformers. However, there is continuous developmental work being done on amorphous core transformers, and the use of this special metal in dry-type transformers may become a practical reality sometime in the future.

If you're considering the use of an amorphous core transformer, you should determine the economic tradeoff; in other words, the price of the unit versus the cost of losses. Losses are especially important when transformers are lightly loaded, such as during the hours from about 9 p.m. to 6 a.m. When lightly loaded, the core loss becomes the largest component of a transformer's total losses. Thus, the cost of electric power at the location where such a transformer is contemplated is a very important factor in carrying out the economic analyses.

Different manufacturers have different capabilities for producing amorphous cores, and recently, some have made substantial advances in making these cores for transformers. The technical difficulties of constructing a core using amorphous steel have restricted the size of transformers using this material. The metal is not easily workable, being very hard and difficult to cut, thin and flimsy, and difficult to obtain in large sheets. However, development of these types of transformers continues; you can expect units larger than 2500kVA being made in the future.

Protection From Harsh Conditions

For harsh environments, whether indoor or outdoor, it's critical that a transformer's core/coil, leads, and accessories be adequately protected.

In the United States, almost all liquid-filled transformers are of sealed-type construction, automatically providing protection for the internal components. External connections can be made with "dead front" connectors that shield the leads. For high corrosive conditions, stainless steel tanks can be employed.

Dry-type transformers are available for either indoor or outdoor installation. Cooling ducts in the windings allow heat to be dissipated into the air. Dry-types can operate indoors under almost all ambient conditions found in commercial buildings and light manufacturing facilities.

For outdoor operations, a dry-type transformer's enclosure will usually have louvers for ventilation. But, these transformers can be affected by hostile environments (dirt, moisture, corrosive fumes, conductive dust, etc.) because the windings are exposed to the air. However, a dry-type can be built using a sealed tank to provide protection from harmful environments. These units operate in their own atmosphere of nonflammable dielectric gas.

Other approaches to building dry-type transformers for harsh environments include cast coil units, cast resin units, and vacuum pressure encapsulated (VPE) units, sometimes using a silicone varnish. Unless the dry-type units are completely sealed, the core/coil and lead assemblies should be periodically cleaned, even in nonharsh environments, to prevent dust and other contaminant buildup over time.

Insulators

Dry-type transformers normally use insulators made from fiber glass reinforced polyester molding compounds. These insulators are available up to a rating of 15kV and are intended to be used indoors or within a moisture-proof enclosure. Liquid-filled transformers employ insulators made of porcelain. These are available in voltage ratings exceeding 500kV. Porcelain insulators are track resistant, suitable for outdoor use, and are easy to clean.

High-voltage porcelain insulators contain oil impregnated paper insulation, which acts as capacitive voltage dividers to provide uniform voltage gradients. Power factor tests must be performed at specific intervals to verify the condition of these insulators.

Regulation

The difference between the secondary's no-load voltage and full-load voltage is a measure of the transformer's regulation. This can be determined by using the following equation:

Regulation (%) = (100)([V.sub.nl] - [V.sub.fl]) / ([V.sub.fl]),

where [V.sub.nl] is the no-load voltage and [V.sub.fl] is the full-load voltage. Poor regulation means that as the load increases, the voltage at the secondary terminals drops substantially. This voltage drop is due to resistance in the windings and leakage reactance between the windings. However, good regulation may offer some other problems.

Voltage regulation and efficiency are improved with low impedance but the potential for serious damage also goes up. Sometimes manufacturers, in order to meet demands for good regulation, design transformers with leakage reactance as low as 2%. A transformer so designed is liable to be severely damaged if a short circuit occurs on the transformer's secondary, especially if the total power on the system is large (a stiff source with low impedance).

The mechanical stresses in a transformer vary approximately as the square of the current. Stresses in a transformer resulting from a short circuit could be approximately six times as great in a transformer having 2% impedance as they would be in one having 5% impedance (where reactance is the major component of the impedance voltage drop).

Of course, a good circuit protection scheme can address this problem. Short circuit integrity is readily available if you wish to include in your transformer specifications that it follow the ANSI/IEEE Guide for Short Circuit Testing; C57.12.90-1993 for wet units and C57.12.91-1995 for dry units.

Voltage Taps

Even with good regulation, the secondary voltage of a transformer can change if the incoming voltage changes. Transformers, when connected to a utility system, are dependent upon utility voltage; when utility operations change or new loads are connected to their lines, the incoming voltage to your facility may decrease, or even perhaps increase.

To compensate for such voltage changes, transformers are often built with load tap changers (LTCs), or sometimes, no-load tap changers (NLTCs). (LTCs operate with the load connected, whereas NLTCs must have the load disconnected.) These devices consist of taps or leads connected to either the primary or secondary coils at different locations to supply a constant voltage from the secondary coils to the load under varying conditions.

Tap changers connected to the primary coils change the connections from the incoming line to various leads going to the coils. When tap changers are connected to the secondary coils, the changing of connections is made from the coils to the output conductors.

Tap changers can be operated by either manual switching or by automatic means. Transformers with tap changers usually have a tap position indicator to allow you to know what taps are being used.

Life Expectancy

There's a common presumption that the useful life of a transformer is the useful life of the insulating system, and that the life of the insulation is related to the temperature being experienced. You should recognize that the temperature of the windings vary; there are so-called hot-spots usually at an accepted maximum 30 [degrees] C above average coil winding temperature for dry-type transformers. The hot-spot temperature is the sum of the maximum ambient temperature, the average winding temperature rise (where the winding refers to the conductor), and the winding gradient temperature (the gradient being the differential between the average winding temperature rise and the highest temperature of the winding).

The nameplate kVA rating of a transformer represents the amount of kVA loading that will result in the rated temperature rise when the unit is operated under normal service conditions. When operating under these conditions (including the accepted hot-spot temperature with the correct class of insulation materials), you should achieve a "normal" life expectancy for the transformer.

Information on dry-type transformer loading from ANSI/IEEE C57.96-1989 indicates that you can have a 20-yr life expectancy for the insulation system in a transformer. However, due to degradation of the insulation, a transformer might fail before an elapse of 20 yrs. For dry-type transformers having a 220 [degrees] C insulating system and a winding hot-spot temperature of 220 [degrees] C, and with no unusual operating conditions present, the 20-yr life expectancy is a reasonable time frame. (The 220 [degrees] C represents a transformer used in a location with a 40 [degrees] C [104 [degrees] F] maximum ambient temperature, an average 150 [degrees] C rise in the conductor windings, and a 30 [degrees] C gradient temperature.)

Most 150 [degrees] C rise dry-type transformers are built with 220 [degrees] C insulation systems. Operating such a transformer at rated kVA on a continuous basis with a 30 [degrees] C average ambient should equate to a "normal" useful life. (Note: 40 [degrees] C maximum ambient in any 24-hr period with 30 [degrees] C as the 24-hr average is considered a standard ambient.)

When based solely on thermal factors, the life of a transformer increases appreciably if the operating temperature is lower than the maximum temperature rating of the insulation. However, you should recognize that the life expectancy of transformers operating at varying temperatures is not accurately known. Fluctuating load conditions and changes in ambient temperature make it difficult, if not impossible, to arrive at such definitive information.

Overloading

For effective operation of an electrical system, transformers are sometimes overloaded to meet operating conditions. As such, it's important that you have an understanding with the transformer manufacturer as to what overloading the unit can withstand without causing problems.

The main problem is heat dissipation. If a transformer is overloaded by a certain factor, say 20% beyond kVA rating for a certain period of time, depending upon that period of time, it's probable that any heat developed in the coils will be transferred easily to the outside of the transformer tank. Therefore, there's a reasonable chance that the overloading will not cause a problem. However, when longer time periods are involved, heat will start to build up internally within the transformer, possibly causing serious problems.

An effective way of removing this heat is to use built-in fans; this way, the load capability can be increased without increasing the kVA rating of the transformer.

Dry-type transformers typically have a fan-cooled rating that is 1.33 times the self-cooled rating. Some transformer designs can provide ratings of 1.4 to 1.5 times self-cooled units. If you have such requirements, you should prepare a carefully written specification.

Liquid-filled transformers, because of their double heat-transfer requirement (core/coil-to-liquid and liquid-to-air), have a lower forced air rating. Usually, the increased rating is 1.15 times the self-cooled rating for small units and 1.25 times self-cooled rating for larger "small power transformers." When above 10MVA, the ratio may be as high as 1.67 to 1.

You should recognize two distinct factors when forced cooling is used. First, the concept is used to obtain a higher transformer capacity; but when doing so, losses are increased substantially. A dry-type transformer operating at 133% of its self-cooled rating will have conductor losses of nearly 1.8 times the losses at the self-cooled rating. And, there will be some losses in the form of power to operate the fan motors. The normal no-load losses remain constant regardless of the load. The other liability is that when additional equipment is used, such as fans, the chance of something malfunctioning increases.

Insulation Level

The insulation level of a transformer is based on its basic impulse level (BIL). The BIL can vary for a given system voltage, depending upon the amount of exposure to system overvoltages a transformer might be expected to encounter over its life cycle. ANSI/IEEE Standards C57.12.00-1993 and C57.12.01-1989 indicate the BILs that may be specified for a given system voltage. You should base your selection on prior knowledge with similar systems, or on a system study such as performed by a qualified engineering firms or by selecting the highest BIL available for the system's voltage.

If the electrical system in question includes solid-state controls, you should approach the selection of BIL very carefully. These controls, which when operating chop the current, may cause voltage transients.

Liquid-Filled Temperature Considerations

Liquid-type transformers use insulation based on a cellulose/fluid system. The fluid serves as both an insulating and cooling medium. Forms are used (which are rectangular or cylindrical shaped) when constructing the windings and spacers are used between layers of the windings. The spacing is necessary to allow the fluid to flow and cool the windings and the core.

For cooling, fluid flows in the transformer through ducts and around the coil ends within a sealed tank that encompasses the core and coils. Removal of the heat in the fluid takes place in external tubes, usually elliptical in design, welded to the outside tank walls.

When transformer ratings begin to exceed 5MVA, additional heat-transfer is required. Here, radiators are used; they consist of headers extending from the transformer tank on the bottom and top, with rows of tubes connected between the two headers. The transformer fluid, acting as a cooling medium, transfers the heat picked up from the core and coils and dissipates it to the air via the tubes.

The paper insulation used today in liquid-filled transformers is thermally upgraded, allowing a 65 [degrees] C average winding temperature rise as standard. Until the '60s, 55 [degrees] C rise was the standard.

Sometimes, transformer specifications are written for a 55 [degrees]/65 [degrees] C rise. This provides an increase in the operating capacity by 12% since the kVA specified is based on the old 55 [degrees] C rise basis but the paper supplied is thermally upgraded kraft type.

For both wet- and dry-type units, a key factor in transformer design is the amount of temperature rise that the insulation can withstand. Lower temperature rise ratings of transformers can be achieved in two ways: By increasing the conductor size of the winding (which reduces the resistance and therefore the heating) or by derating a larger, higher temperature rise transformer. Be careful when using the latter method; since the percent impedance of a transformer is based on the higher rating, the let-through fault current and startup inrush current will be proportionately higher than the rating at which it is being applied. Consequently, downstream equipment may need to have a higher withstand and interrupting rating, and the primary breaker may need to have a higher trip setting in order to hold in on startup.

The lower temperature rise transformers are physically larger and, therefore, will require more floor space. On the plus side, a lower temperature rise transformer will have a longer life expectancy. The latest energy codes recommend selecting transformers to optimize the combination of no-load, part-load, and full-load losses without compromising the operational and reliability requirements of the electrical system.

Dry-Type Temperature Considerations

Dry-type transformers are available in three general classes of insulation. The main features of insulation are to provide dielectric strength and to be able to withstand certain thermal limits. Insulation classes are 220 [degrees] C (Class H), 185 [degrees] C (Class F), and 150 [degrees] C (Class B). Temperature rise ratings are based on full-load rise over ambient (usually 40 [degrees] C above ambient) and are 150 [degrees] C (available only with Class H insulation), 115 [degrees] C (available with Class H and Class F insulation) and 80 [degrees] C (available with Class H, F, and B insulation). A 30 [degrees] C winding hot spot allowance is provided for each class.

The lower temperature rise transformers are more efficient, particularly at loadings of 50% and higher. Full load losses for 115 [degrees] C transformers are about 30% less than those of 150 [degrees] C transformers. And 80 [degrees] C transformers have losses that are about 15% less than 115 [degrees] C transformers and 40% less than 150 [degrees] C transformers. Full load losses for 150 [degrees] C transformers range from about 4% to 5% for 30 kVA and smaller to 2% for 500 kVA and larger.

When operated continuously at 65% or more of full load, the 115 [degrees] C transformer will pay for itself over the 150 [degrees] C transformer in 2 yrs or less (1 year if operated at 90% of full load). The 80 [degrees] C transformer requires operation at 75% or more of full load for a 2-yr payback, and at 100% load to payback in 1 yr over the 150 [degrees] C transformer. If operated continuously at 80% or more of full load, the 80 [degrees] C transformer will have a payback over the 115 [degrees] C transformer in 2 yrs or less (1.25 years at 100% loading).

You should note that at loadings below 50% of full load, there is essentially no payback for either the 115 [degrees] C or the 80 [degrees] C transformer over the 150 [degrees] C transformer. Also, at loadings below 40%, the lower temperature rise transformers become less efficient than the 150 [degrees] C transformers. Thus, not only is there no payback, but also the annual operating cost is higher.

Losses

Because the cost of owning a transformer involves both fixed and operating costs, and because the cost of electric power is constantly on the rise, the cost of energy lost over a period of time due to a transformer's losses can substantially exceed the purchase price of a unit. As such, it's important that you evaluate transformer no-load and load losses carefully.

No-load losses consist of hysteresis and eddy currents in the core, copper loss due to no-load current in the primary winding, and dielectric loss. The core losses are the most important.

Load losses include FR loss in the windings, FR losses due to current supplying the losses, eddy current loss in the conductors due to leakage in the field, and stray losses in the transformer's structural steel. Specifying higher efficiency requires larger conductors for the coils to reduce FR losses. This means added cost, but the payback may be significant.

K-Factor

Some transformers (liquid- and dry-type) are now being offered with what is called a k-factor rating. This is a measure of the transformer's ability to withstand the heating effects of nonsinusoidal harmonic currents produced by much of today's electronic equipment and certain electrical equipment. Because of the problems created by harmonics, ANSI/IEEE, in the late 1980s, formulated the C57.110-1986 standard, Recommended Practice for Establishing Transformer Capability When Supplying Nonsinusoidal Load Currents. It applies to transformers up to 50MVA maximum nameplate rating when these units are subject to nonsinusoidal load currents having a harmonic factor exceeding 0.05 per-unit (pu), the percent value of the base unit. (Harmonic factor is defined as the ratio of the effective value of all the harmonics to the effective value of the fundamental 60-Hz frequency.)

In December, 1990, UL announced listings for dry-type general purpose and power transformers affected by nonsinusoidal currents in accordance to the above ANSI/IEEE C57.110-1986. The "listing investigation" is directed to submitting transformers for testing to certain factors relating to rms current at certain harmonic orders in a specified way that correlates with heating losses. The factors involved in the tests are collectively called the k-factor.

Transformers meeting k-factor requirements also address the need for providing for high neutral currents. Because the neutral current may be considerably greater than the phase current, the neutral terminal of the transformer is sometimes doubled in size for additional customer neutral cables. It's important that you recognize the impact caused by harmonic currents.

Oversized primary conductors are used to compensate for circulating harmonic currents. The secondary is also given special consideration. As the frequency increases to 180 Hz (as in the case with the 3rd harmonic), and greater, the skin effect (where current begins to travel more on the circumference of the conductor) becomes more pronounced. To compensate for this, the windings are composed of several smaller sizes of conductor, with the circumference of the total conductors being greater. The transformer design also incorporates a reduction in core flux to compensate for harmonic voltage distortion.

For help in determining what k-factor to use when you specify a transformer while designing an electrical system for a facility, identify what harmonic producing equipment is going into the system. Then, obtain information on the harmonic spectrum and the associated amplitudes produce by the offending apparatus from the manufacturer of the equipment.

Cautionary note: Be careful when using k-rated transformers having abnormally low impedance, particularly those units with ratings of k-20 and higher. Such low impedance transformers can actually increase harmonics neutral current problems and even cause some loads to malfunction or cause damage to equipment! Use of abnormally low impedance transformers will act to significantly increase the neutral current and, therefore, negate some of the benefits of doubling the neutral conductors. It's important that isolation transformers be used for high harmonic loads having normal (3% to 6%) impedance. Some highly knowledgeably engineers believe that it's wrong to specify transformers with ratings k-20 and higher for commercial office loads. If the harmonics are of such high magnitude and it's believed a transformer with a rating of k-20 or higher should be used, then careful attention should be given to make sure that the impedance of the unit be at least 3%.

Shielding

Depending upon the loads being served, the ability of a transformer to attenuate electrical noise and transients would be a helpful attribute. While what is commonly referred to as "dirty power" possibly can't be stopped at the source causing the noise, corrective measures can be taken, including the application of a shield between the primary and secondary of a transformer. This type of construction is usually considered when a distribution transformer is serving solid-state devices such as computers and peripheral equipment.

There are two types of noise and voltage transients: common mode noise and transients and normal or transverse mode noise and transients. Common mode power aberrations are disturbances between the primary lines and the ground (phase-to-ground); transverse mode power aberrations are line-to-line disturbances. It is important to recognize this difference because an electrostatic shield will not reduce transverse disturbances. However, transverse disturbances are slightly reduced by a transformer's impedance, and this is true whether or not a transformer has a shield.

To substantially reduce transverse mode power aberrations, surge suppressors are used to handle the transients, and filters are used to handle the noise. Some literature show voltage sine curves with disturbances imposed on the curve as well as clean voltage sine curves, and information is included to the effect that an electrostatic shield is responsible for reducing or eliminating the disturbances. This is incorrect because the voltage sine curve portrays line-to-line characteristics, and shielding has no effect upon such disturbances.

An electrostatic shield is a grounded metal barrier between the primary and secondary that filters common mode noise, thus delivering cleaner power and reducing the spikes caused by common mode voltage transients. The shield takes most of the energy from the voltage spike and delivers it to the ground. A number of authorities agree that transformers built to deliver a 60 decibel (dB) (a 1000-to-1 ratio) reduction in common mode disturbances (noise and voltage transients) will help solve or prevent such power aberrations from causing problems. Some transformers are built with the ability to provide a 100 dB (100,000-to-1 ratio) attenuation, and even larger ratios. If poor power quality may be a problem on a system where you plan to install a transformer, get information on the unit's attenuation ratio and verify that the power problem stems from common mode disturbances.

An example of the effect of attenuation would be a lightning strike that induces a 1000V spike on a power line connected to the primary of a transformer. A shield would take most of this energy to ground, and if the attenuation is 60 dB (1000-to-1 ratio), an approximate a IV "bump" will be passed to the secondary and onto the feeder or branch circuit. A number of loads can take a "bump" of this magnitude without damage. If there's a branch circuit and another shielded transformer ahead of a load, the "bump" will be further reduced by the second transformer. This type of reduction is caused by an effect called transformer cascading.

Placing Transformers Near The Load

Locating a transformer indoors, on the rooftop, or adjacent to a building in order to minimize the distance between the unit and the principal load results in reducing energy loss and voltage reduction. It also reduces the cost of secondary cable.

On the other hand, such placements of high-voltage equipment require closer consideration of electrical and fire safety issues. These conflicting goals can be satisfied by using transformers permitted by Code and insurance companies.

When liquid-filled transformers are preferred, less-flammable liquids are widely recognized for indoor and close building proximity installations. Wet-type transformers using less-flammable, or high fire point liquids, have been recognized by the NEC since 1978 for indoor installation without the need for vault protection unless the voltage exceeds 35kV. Based on this type of transformer's excellent fire safety record, Code and insurance restrictions have become minimal. Conventional mineral oil units are allowed indoors, but only if they are installed in a special 3-hr-rated vault (with a few exceptions) per the construction requirements of NEC Article 450, Part C. There's a requirement for liquid containment when wet-type transformers are used, regardless of the type fluid employed.

When dry-type units are preferred, they have fewer code restrictions. Obviously, these types of transformers do not need liquid containment. Per the requirements listed in NEC Sec. 450-21, there are minimum clearances that you must observe, and units over 112.5kVA require installation in a transformer room of fire-resistant construction, unless they are covered by one of two listed exceptions. As with liquid units, dry transformers exceeding 35kV must also be located in a 3-hr-rated vault.

A liquid-filled transformer may experience leakage around gaskets and fittings; however, if the installation was carried out correctly, this should not be a problem. Major maintenance procedures may require inspection of internal components, meaning that the coolant will have to be drained. Coils in liquid-type units are much easier to repair than coils in dry-type transformers. Cast coils are not repairable; they must be replaced.

Accessories

Accessories are usually an added cost, and sometimes they are installed while the transformer is being bulk. Therefore, you should have some knowledge of accessories and incorporate in the transformer specification those accessories that, when installed, would be beneficial to the transformer's performance. Some of the accessories available include the following:

* Stainless steel tank and cabinet for extra corrosion protection (liquid-filled only);

* Special paint/finishes for corrosive atmospheres and ultraviolet light (liquid-filled only);

* Weather shields for outdoor units, protective provisions for humid environments, and rodent guards (dry-type only);

* Temperature monitors. There are a number of options available from simple thermometers to more extensive single- or 3-phase temperature monitoring as well as options for contacts to initiate alarms and/or trip circuits as well as starting cooling fans;

* Space heaters to prevent condensation during prolonged shutdown (usually with thermostats);

* Optional location of openings for primary and secondary leads;

* Special bushings for connecting primary to right-angle feeders;

* Loadbreak switches installed in transformer cabinet or a closely coupled cabinet;

* Tap changing control apparatus (usually a nonload device that can change the output voltage by about 5%);

* Internal circuit protection devices to open primary line when there-are short circuits and severe overloads;

* Equipment such as liquid level gauges, drain valves, radiator guards, sampling devices, and pressure relief valves (for liquid-filled transformers only);

* Internal lightning arresters;

* Internal surge arresters for protection against line or switching surges;

* Provisions for current and potential transformers and metering;

* Future fan provision for such installation at a later date;

* Key interlocks or padlocks to coordinate opening of enclosure panels with operation of HV switch;

* Provisions for ground fault detection;

* Installation of small control power transformers in cabinet to operate various 120/240V accessories for medium-voltage transformers; and

* Seismic bracing for units installed at locations subject to earthquakes.

Power Quality Maintenance Program

2012-02-14T11:14:00.000+07:00

A recent project with one of the utility's major industrial customers is a prime example of how the use of select power quality indices in a predictive/preventive maintenance program (PPM), coupled with the use of digital metering with power quality recording capabilities, can help industrial facilities develop an effective power quality maintenance program. The intent of this particular program was to remotely retrieve and automatically compile indices to provide reporting based on threshold events and provide histogram trending to be used to determine operational limits.

The most difficult part of implementing this program was to establish limits for trended indices, because there is very little published information on acceptable power quality operating limits for equipment, making this task more of an art than a science. The equipment manufacturers' task of testing the effects of a boundless number of index variations on their equipment is understandably impractical.

The approach of this power quality maintenance program somewhat follows a typical yearly doctor's exam. In my case, the doctor checks my blood pressure against my historical trend data and tells me it's above average published levels. Because it's always been in this range, however, it's considered normal for me. So pending any apparent abnormalities, I'm basically good until next year.

With this type of thinking in mind, we established initial limits for this program based on a number of standards and guidelines, such as IEEE 1159, CSA CAN-3-C235, ANSI/NEMA MG1, ITIC curves, electric utility power quality limits, and the operating history of the monitored distribution equipment. After initially applying these limits — if no power quality abnormalities were apparent with the trended indices — the benchmarked limits were adjusted as required to minimize event reporting.

Differentiating between acceptable and abnormal power quality events did require a degree of experience for expedient analysis. However, as per typical troubleshooting approaches, the investigations were all based on event timing to narrow in on offending equipment or processes. The program used feeder and equipment recorders that had the functionality to trend maximum, minimum, and average power quality indices, such as harmonics, unbalance, sags, and surges. The recorders were networked together and downloaded remotely. A database program was developed that performed statistical calculations, graphing, and exception event reporting on the available data.

Having a full array of indices is beneficial; however, any number available will fit the trending requirement. In this case, our team was fortunate enough to have facilities that placed permanent recorders with power quality capability throughout the plant at all levels of distribution as well as at some critical pieces of equipment. We used the following indices as prime indicators of distribution performance:

Figure-1

Voltage variation (average, minimum, maximum) — This index (Figure-1) was trended, typical electric utility planning limits of ±5% were applied for voltages greater than 1,000V, and CSA CAN-3-C235 Preferred Voltage Levels for AC Systems, 0 to 50,000V, Electric Power Transmission and Distribution was applied for voltages less than 1,000V. These limits were never adjusted any tighter than the initial values.

Current (average, minimum, and maximum) — This index was not used for alarming but trended to support comparative analysis.

Sag (if available) — This index was extremely crucial to capture, as it is quite often the leading culprit of lost production. IEEE Standard 1159, “Recommended Practice for Monitoring Electric Power Quality,” was used to define the sag level, and these events were loosely compared with the ITIC curve. However, the facility's immunity threshold to sag events was the ultimate limit.

Voltage unbalance (average) — Average voltage variation was trended, and typical limits of between 1% to 2% were used while respecting ANSI/NEMA MG1 Motors and Generators standard. This limit was never adjusted any tighter than the initial values.

Current unbalance (average) — This index was not used for alarming, but trended to support comparative analysis.

Figure-2

Voltage total harmonic distortion (average) — This index (Figure-2) was trended, and a typical IEEE 519 planning limit of 5% of the average fundamental voltage was applied. This limit was lowered as we became more confident with the trended bandwidth variability, with the overall intent of minimizing event reporting.

Voltage individual harmonic distortion (average 2nd through 15th) — This index was trended, and typical IEEE 519 planning limits of 3% of the average fundamental voltage were applied. These limits were lowered as we became more confident with the trended bandwidth variability, with the overall intent of minimizing event reporting.

Figure-3

Current total demand distortion (average) — This index (Figure-3) was trended, and typical IEEE 519 planning limits were applied based on the short circuit over maximum demand loading ratio (Isc/Il). Within the facility, transformer nameplate kVA was used for both the maximum demand loading (Il) and for normalizing. This limit was lowered as we became more confident with the trended bandwidth, with the overall intent of minimizing event reporting.

Current individual demand distortion (average 2nd through 15th) — This index was trended, and typical IEEE 519 planning limits were applied based on the short circuit over maximum demand loading ratio (Isc/Il). Within the facility, transformer nameplate kVA was used for both the maximum demand loading (Il) and for normalizing. These limits were lowered as we became more confident with the trended bandwidth variability, with the overall intent of minimizing event reporting.

Power [average - energy (W), demand charge (VA) and reactive energy (var)] — These indices were not used for alarming but trended to support comparative analysis.

A customized, off-the-shelf database program was configured as a preliminary platform to perform three major routines: statistical calculations, exception event reporting, and graphing of the recorded indices. The statistical analysis toolbox simply used minimum, maximum, average, percentile, and standard deviation to help weight the selected limits — no statistical expertise was required. The statistical analysis toolbox was applied during the early stages of the program. Once a confident operating bandwidth was evident, the limits were adjusted on an as-needed basis to minimize reporting.

The exception event reporting toolbox identified indices outside of limits, logging events by magnitude and date of incident. The exception event reporting toolbox was continually used to report on out of limit events. Any automatic reporting period or report can be generated from printed report to e-mail notification. The graphing toolbox allowed the graphing of selected indices for comparative analysis.

Interestingly enough, the initial success of this program has been to immediately identify suspect equipment operation and improperly configured metering as opposed to the intent of trending and identifying progressive equipment failure. Typical power quality equipment issues ranged from high harmonic distortion due to capacitor resonance, voltage unbalance due to failed power factor correction stages, high even harmonic current due to faulty rectifier bridges, and multiple sags due to equipment starts. Typical metering configuration issues ranged from incorrect ratios, time stamps, inconsistent trigger settings, and mislabeled equipment. Longer term trending identified electric utility seasonal system feeder configuration changes that were otherwise thought to be constant. These different system feeder configurations changed the applied harmonic voltage spectrum and the facility resonance points.

This program successfully demonstrated a proactive approach to reduce facility downtime while effectively minimizing the resources required to assess the unrelenting amount of data produced by the recorders. Not only did the continuous monitoring strategy benchmark electrical feeder power quality characteristics and report only when limits were exceeded, but it also successfully demonstrated that a power quality maintenance program can be implemented without considerable power quality expertise.

Electrical Calculation Basics : Single and 3-Phase Parameters

2012-02-14T11:13:00.000+07:00

Welcome to the first in a series of articles focusing on electrical calculation basics. This month, we'll discuss the most fundamental of calculations — those for current (I) and kilowatts (kW). We'll also show you how you can do these calculations “in your head,” with very reasonable accuracy, through the use of constants.

You may ask, “What exactly is a constant?” An example of a constant with which you're very much familiar is pi (π), which is derived by dividing a circle's circumference by its diameter. No matter what the circumference and diameter of the respective circle, their ratio is always pi. You can use constants that apply to specific single- and 3-phase voltages to calculate current (I) and kilowatts (kW). Let's see how to do this.

Single-Phase Calculations

Basic electrical theory tells us that for a single-phase system,

kW = (V × I × PF) ÷ 1,000.

For the sake of simplicity, let's assume the power factor (PF) is unity. Therefore, the above equation becomes

kW = (V × I) ÷ 1,000.

Solving for I, the equation becomes

I = 1,000kW ÷ V (Equation 1)

Now, if we look at the “1,000 ÷ V” portion of this equation, you can see that by inserting the respective single-phase voltage for “V” and dividing it into the “1,000,” you get a specific number (or constant) you can use to multiply “kW” to get the current draw of that load at the respective voltage.

For example, the constant for the 120V calculation is 8.33 (1,000 ÷ 120). Using this constant, Equation 1 becomes

I = 8.33kW.

So, if you have a 10kW load, you can calculate the current draw to be 83.3A (10 × 8.33). If you have a piece of equipment that draws 80A, then you can calculate the relative size of the required power source, which is 10kW (80 ÷ 8.33).

By using this same procedure but inserting the respective single-phase voltage, you get the following single-phase constants, as shown in Table 1.

3-Phase Calculations

For 3-phase systems, we use the following equation:

kW = (V × I × PF × 1.732) ÷ 1,000.

Again, assuming unity PF and solving this equation for “I,” you get:

I = 1,000kW ÷ 1.732V.

Now, if you look at the “1,000 4 1.732V” portion of this equation, you can see that by inserting the respective 3-phase voltage for “V” and multiplying it by 1.732, you can then divide that quantity into the “1,000” to get a specific number (or constant) you can use to multiply “kW” to get the current draw of that 3-phase load at the respective 3-phase voltage. Table 2 lists each 3-phase constant for the respective 3-phase voltage obtained from the above calculation.

Power Systems and SCADA System Contain Protective Devices to Prevent Injury or Damage During Failures

2012-01-23T13:07:00.000+07:00

The quint essential protective device is the fuse. When the current through a fuse exceeds a certain threshold, the fuse element melts, producing an arc across the resulting gap that is then extinguished, interrupting the circuit. Given that fuses can be built as the weak point of a system, fuses are ideal for protecting circuitry from damage. Fuses however have two problems: First, after they have functioned, fuses must be replaced as they cannot be reset. This can prove inconvenient if the fuse is at a remote site or a spare fuse is not on hand. And second, fuses are typically inadequate as the sole safety device in most power systems as they allow current flows well in excess of that that would prove lethal to a human or animal.

The first problem is resolved by the use of circuit breakers - devices that can be reset after they have broken current flow. In modern systems that use less than about 10 kW, miniature circuit breakers are typically used. These devices combine the mechanism that initiates the trip (by sensing excess current) as well as the mechanism that breaks the current flow in a single unit. Some miniature circuit breakers operate solely on the basis of electromagnetism. In these miniature circuit breakers, the current is run through a solenoid, and, in the event of excess current flow, the magnetic pull of the solenoid is sufficient to force open the circuit breaker's contacts (often indirectly through a tripping mechanism). A better design however arises by inserting a bimetallic strip before the solenoid - this means that instead of always producing a magnetic force, the solenoid only produces a magnetic force when the current is strong enough to deform the bimetallic strip and complete the solenoid's circuit.

In higher powered applications, the protective relays that detect a fault and initiate a trip are separate from the circuit breaker. Early relays worked based upon electromagnetic principles similar to those mentioned in the previous paragraph, modern relays are application-specific computers that determine whether to trip based upon readings from the power system. Different relays will initiate trips depending upon different protection schemes. For example, an overcurrent relay might initiate a trip if the current on any phase exceeds a certain threshold where as a set of differential relays might initiate a trip if the sum of currents between them indicates there may be current leaking to earth. The circuit breakers in higher powered applications are different too. Air is typically no longer sufficient to quell the arc that forms when the contacts are forced open so a variety of techniques are used. The most popular technique at the moment is to keep the chamber enclosing the contacts flooded with sulfur hexafluoride (SF6) - a non-toxic gas that has superb arc-quelling properties.

The second problem, the inadequacy of fuses to act as the sole safety device in most power systems, is probably best resolved by the use of residual current devices (RCDs). In any properly functioning electrical appliance the current flowing into the appliance on the active line should equal the current flowing out of the appliance on the neutral line. A residual current device works by monitoring the active and neutral lines and tripping the active line if it notices a difference. Residual current devices require a separate neutral line for each phase and to be able to trip within a time frame before harm occurs. This is typically not a problem in most residential applications where standard wiring provides an active and neutral line for each appliance (that's why your power plugs always have at least two tongs) and the voltages are relatively low however these issues do limit the effectiveness of RCDs in other applications such as industry. Even with the installation of an RCD, exposure to electricity can still prove lethal.

SCADA Systems

In large electric power systems, Supervisory Control And Data Acquisition (SCADA) is used for tasks such as switching on generators, controlling generator output and switching in or out system elements for maintenance. The first supervisory control systems implemented consisted of a panel of lamps and switches at a central console near the controlled plant. The lamps provided feedback on the state of plant (the data acquisition function) and the switches allowed adjustments to the plant to be made (the supervisory control function). Today, SCADA systems are much more sophisticated and, due to advances in communication systems, the consoles controlling the plant no longer need to be near the plant itself. Instead in today's power systems, it is increasingly common for plant to be controlled from a central remote site with equipment similar to (if not identical to) a desktop computer. The ability to control such plant through computers has increased the need for security and already there have been reports of cyber-attacks on such systems causing significant disruptions to power systems.

The Isolation Transformer Which Offers Different Applications and Purposes

2012-01-23T13:06:00.000+07:00

A transformer is a tool commonly used to transfer electrical energy from a certain circuit to another circuit by means of inductively tied conductors. These conductors are made up of two or more ferromagnetic coils named as windings. When there are any electrical alterations made in the main winding, this creates a sporadic magnetic field in the core. Thus, it will reproduce a fluctuation that includes the field on both sides of secondary winding. As a result, it provides intermittent electrical energy in the secondary coils. There are various forms of transformers that help transfer electrical power. One popular form is the isolation transformer, which offers different applications and purposes.

An isolation transformer is often used to convey electrical power coming from a source of alternating current (AC) power to a certain device, where the powered device is being isolated from the power source for safety measures. It can also be used to thwart capacitance that enhances the primary and secondary winding linkage causing a higher frequency sound. Normally, a transformer could increase energy voltage level from one stage to another through induction of electrical energy from one winding to another. With the beauty of isolation, the circuits of input and output are secluded from each other and will never be in contact. Isolation transformers provide galvanic isolation that is utilized for protection against electric shock, suppression of electrical noise in various receptive and sensitive gadgets, and transmission of power among two circuits.

This unique transformer is suitably designed to oppose the interference caused by ground loops and to minimize the coupling of the windings through construction that minimizes capacitive coupling. The transformers often utilize unconnected bobbins on both coil windings. However, the windings are only wounded on top of each other with insulation in the middle. Most of them have electrostatic shields between windings that are used for power supplies on sensitive equipment like computers, laboratory gadgets, and other electronic materials.

Typically, any transformer has an isolating function, whether it is used to send power or signals. However, those transformers whose sole purpose is to isolate circuits are usually described as isolation transformers. It has a built-in special insulation placed between primary and secondary windings. It is discernible to hold out a high voltage of a thousand to four thousand volt range.

Their main focus is on capacitive coupling among the two windings. Aside from the capacitance of the primary and secondary windings, they also fasten the AC power from the primary to the secondary winding. Some of the examples of isolated transformers include very small transformers, such as four transformers in a minute dual in-line chip package that are used to isolate high-frequency low-voltage pulse circuits. They are quite expensive compared to conventional transformers.

An isolation transformer offers various functions. Most of these purposes carried out by isolation transformers are often used in different industries and business establishments. Listed below are some of the outstanding roles of isolation transformers.

It can substitute isolation in different circuits. There are industries and establishments that use different applications in isolating the circuits without increasing or decreasing the electric current. Anisolation transformer can separate the primary and secondary windings with a "one-is-to-one" ratio.

It protects people from the danger of electrocution. Custom power transformers facilitate separation of the person from the resource to provide safety. It will unite a vessel to an electric power source. However, it can be done in a manner that the electric wiring will not touch directly to the power line.

Isolation transformers could reduce noise and other kinds of sound. These can prevent any sound or noise created by connecting the signal of the audio amplifier to the speaker output circuit without any connection created between the two, separating the amount produced by the audio amplifier to the piece of module from the amplifier.

It helps isolation of the radio frequency. It is essential to separate the amount generated by a radio frequency on the large devices of the circuit from the transmitter line. Thus, an isolation transformer facilitates the connection of the amount produced by the radio frequency amplifier to the transmitted signals towards the direction of the antenna.

It facilitates direct current (DC) power isolation. Telephone lines often utilize digital information that needs amplifiers on various intervals. Isolation transformers carry out the separation of direct current components from the signal to the control of every amplifier on the line. An isolation transformer can carry out the task in the input and output of each amplifier.

A "one-to-one" ratio of power transformer is often chosen as an isolation transformer when used in electronics testing and servicing for safety purposes. Without this isolation, there might be danger in touching a live part of the circuit. Thus, isolation transformers became an excellent option for most gadgets that require the use of electricity.

Offshore Wind Turbine Power with Reduce The Costs

2012-01-12T14:50:00.002+07:00

Meeting the first target of 40GW by 2010 requires the manufacture and installation of around 10,000 wind turbines; and there are several logistical challenges that must be overcome to achieve this aim. Offshore wind power is at an early stage of development, and there remains a necessity to streamline all aspects of the supply chain from component manufacture, to turbine design, to installation processes.

Offshore wind power as an industry is set to undergo intense growth over the next 10-20 years. The EWEA (European Wind Energy Association) has established targets of 40GW of offshore wind power production by the year 2020, and 150GW by 2030. This move towards a European grid represents a 28% annual increase in market growth; it will enable the trade of electricity between states, and cement Europe's status as technological leaders in the wind power industry.

Turbines

The designs of offshore turbines were generally borrowed or adapted from their onshore counterparts; so production of offshore wind turbines had been reliant to an extent on the market growth of the onshore industry. As recently as 2008 this led to supply shortages during periods of high onshore demand. Offshore wind power, however, must be viewed as an entirely different concept to onshore wind power. With the potential for larger turbines, and no limitations on aesthetics or noise levels, manufacturers are developing specifically designed offshore turbines which could increase to up to 10MW in capacity.

Siemens, for example is currently supplying its SWT-3.6-120 turbines for use in the London Array project. The 3.6MW turbine has a 120m rotor, and the three-bladed cantilevered construction will start to produce electricity at wind speeds of 7mph. Supply and installation, however, consists of shipping the turbines from Denmark to the UK, transferring them from barges to installation vessels, before installing the turbine, the hub, and finally the blades.

To establish mass production and cost efficiency of supply and installation, there are several initiatives in development, and various logistical problems to navigate. Design is moving towards the creation of more 'intelligent' turbines, with advanced control monitoring and preventative maintenance. While the development of 'simple' turbines with fewer moving parts designed to be changed easily, will also significantly reduce costs both in terms of construction and operation and maintenance.

1 Spinner 2 Spinner bracket 3 Blade 4 Pitch bearing 5 Rotor hub 6 Main bearing 7 Main shaft 8 Gearbox 9 Service crane 10 Brake disc 11 Coupling 12 Generator 13 Yaw gear 14 Tower 15 Yaw ring 16 Oil filter 17 Generator fan 18 Canopy

Exploded view of Siemens SWT-3.6-20 nacelle, Source: siemens.com

The concept of a twin blade, downwind turbine is at design stage and could appear on the market in the coming years. Twin blades are much louder than three-bladed turbines so have not been considered appropriate for onshore development. There are no concerns over noise levels offshore, and installation could be a much quicker process as nacelles can be stacked with the rotor pre-mounted, rather than installing one of the blades at sea.

A variable speed, direct drive turbine is another possibility in the near future. Gearboxes are one of the most difficult parts to replace on a turbine, and multi-pole gearless turbines operate at a lower drive train speed which would decrease the amount of stress placed on other components. Gearless turbines are generally much heavier than those with conventional gearboxes, so designs must be produced with lighter components to reduce the weight at the top of the tower before this can become a reality.

Wind turbines are currently manufactured in such a way that any part or component cannot be replaced easily. Due to the difficulty in accessing wind farms far out at sea, and the problems of on-site repairs, it is important that purpose built offshore turbines are designed with operation and maintenance in mind. At the moment O&M is very much site specific, and as the industry learns more from existing wind farms, so the process can be standardized to create a sub-industry purely surrounding O&M. It is reasonable to expect to see swing-off systems being introduced, which will allow a spare nacelle to be fitted whilst one is undergoing a service. Preventative, automated systems that can carry out oil and filter changes without the need for humans are also on the horizon. Other initiatives such as multi-coated blades and modular drive trains will help to reduce the amount of maintenance required, and therefore reduce the amount of downtime for each turbine.

Foundations

The substructure of a turbine is one of the largest single cost factors of the overall project, and reducing the cost of construction, transportation and installation of these foundations will have a big impact on supply chain optimization. Again, much of the technology has been adapted from onshore foundations with monopoles being the most common substructure in use on offshore wind farms today. The design of specific offshore foundations, with reduced manufacturing costs is essential to ease this link in the supply chain.

Crucially, wind speed and therefore potential power production, increase greatly in deeper water. Several different concepts are being tested to enable the installation of 10MW or larger turbines on wind farms at depths of 60 meters or more.

One such design is the Sway concept produced by the Norwegian company of the same name. The floating tower can be installed in depths of up to 400 meters, taking advantage of higher wind speeds. The tower is filled with ballast, and the center of gravity is much lower than the towers center of buoyancy thus giving it stability. It is a unique concept as the blades face downwind, and the entire turbine can rotate to suit the direction of the wind; this optimizes the amount of power generated from the wind, while at the same time reducing the stress on components. Sway claim that reduced manufacturing costs, a long life span, and the ability to support large turbines make this a viable and economic option.

Onshore Construction

The manufacture and assembly of turbines at quayside is a big driver in cost reduction. Large sites will be needed to produce as much as possible close to the harbor and reduce transportation costs. Equally, the design of turbines and foundations as a single entity is being considered, rather than viewing them as separate processes.

Sourcing the necessary materials to produce wind turbines could also prove to be an issue when it comes to the supply chain. Norwegian foundation manufacturer, Seatower has designed a gravity base foundation which can be deployed at 50 meters in depth, and can be floated to site pre-commissioned, without the use of cranes for installation.

Ports and Harbours

To enable onshore construction and the development of the offshore wind energy industry, suitable ports and harbors must be purpose built, or current harbors must be renovated. According to a presentation by Chris Ehlers, MBA, MD renewable divisions, Siemens PLC, the following requirements would be needed to facilitate pre-assembly onshore:

• Storage areas of approximately 60,000 to 250,000 square meters.

• A dedicated, private road between storage areas and quayside.

• A quay length of between 150 and 250 meters.

• A quay load-bearing capacity of 3-6 tonnes per square meter.

• A seabed of sufficient bearing capacity.

• A minimum draft of 6 meters.

• Warehouse facilities of between 1000 and 1,500 square meters.

• Access for small vessels such as barges.

• Access for heavy and oversized trucks.

• License and approvals for helicopter transfers.

• Availability for the whole project installation.

The port of Bremerhaven in Germany is an example of the redevelopment of an area with the specific needs of the wind energy industry in mind. When its previous industries of shipping, shipbuilding and commercial fishery suffered an economic downturn in the 1990’s, the local authorities looked to the wind power industry as an alternative. As an industrial area it now houses two offshore wind turbine manufacturers in REpower and Multibrid, Blade manufacturer PowerBlades, which makes blades for Repowers 5MW and 6MW turbines, and Weserwind Offshore Construction, which designs and manufactures heavy steel offshore foundation structures.

The coming together of design, manufacture, storage, pre-assembly and installation from one purpose designed site will have a significant impact on the cost factors that currently hinder supply chain management. An integrated approach to the wind energy industry allows a site such as Bremerhaven to test and carry out research and development in near offshore conditions, it allows for manufacture on-site, and reduces transportation time and cost. It allows manufacturing companies to work closely together, and offers the potential for foundations and turbines to be taken directly to site from production plant by installation vessels working from the same harbor.

Several technologies and industries must co-operate to facilitate the cost reduction of the supply chain of the offshore wind energy industry as a whole. While many sectors of the industry are still in their infancy, there is an emphasis on design to drive down cost; as well as a focus on learning from the experiences of current wind farms to further smooth the processes of supply chain management. The pursuit of renewable energy from offshore wind is unabated, however, and the next ten to twenty years will see a dramatic improvement in the economic viability of offshore wind power.

Energy management monitoring is a skill which every managerial team needs

2012-01-12T14:50:00.001+07:00

Energy management monitoring is important for any company’s decision makers to have important information on how to identify trending in energy use for its operations. This helps major decision makers of a company to be able to generate sound conclusions and prepare for consequences. Using trend graphs from multiple scenarios must be compiled with benchmarks at it will also help in efficient reporting.

An accurate monitoring system enables an enterprise to administer its operations. To help assess its efficiency in operations, a company should set benchmarks in evaluating actual productivity against what it has planned to achieve.

Given that energy is already an expensive resource for any type of business, having an energy management monitoring program helps a company attain efficiency. Legislation that regulate the use of energy has risen due to the rising threats of global warming and the consequent increased carbon emissions from using fossil fuels.

Carbon emissions will be heavily regulated in the future and carbon becomes tradable commodity. It is therefore important to immediately identify areas of wasted energy through an efficient energy management monitoring. Any company of the future will have to mind maximum efficiency in all its operations due to the considerable costs not only from losses due to increased operating expenses but also from penalties on heavy carbon emissions.

Energy was once a commodity which most enterprises did not have that much control of in the past. In this day and age, energy control is now a top priority. Software solutions are also available that control results down to assets level and could help companies in their energy management monitoring initiatives. This will help ensure that every element is optimized in operations.

With the increasing awareness and incentives for cleaner production, companies which have a very efficient energy management monitoring process taking place will have very good chances of availing regional and state grants for efficiency in energy use.

Organizations of the future will be subjected to mandatory carbon emissions reporting, including a full inventory of assets that use energy with corresponding meters. A full life cycle analysis of assets will help ensure that companies account for all sources of energy and sources of greenhouse gas emissions within or without their control.

To get the best utility rates, a smart grid functionality and active energy response can help ensure that any company’s assets are operating in optimum conditions. To strive for efficient performance with the use of energy management monitoring will include using the most current and high quality software solution that can help ensure best use of alternative sources of energy.

Energy management monitoring is a skill which every managerial team needs to understand as the era goes into the low carbon economy age. Companies that fail to conform to energy efficient productions will be heavily penalized through monetary penalties expressed in legislation. Companies will be compelled to comply with cleaner production practices as consumers are becoming highly aware of the environmental consequences and could affect companies by withdrawal of patronizing products.

Build Wind Energy Technology to Renewable Energy Supply

2012-01-07T21:33:00.001+07:00

Wind Turbines For The Home generally comprise a rotor (blades), generator or alternator mounted on a frame, tail, tower, grounding system, wiring and controllers, and inverters (grid-connected systems) or batteries (not connected systems). Wind turbines for your home systems generally consist of blades, a rotor, a generator or alternator mounted on a frame, a tail (usually), a tower, wiring, and "balance of system" components. Home wind energy systems are clean sources of power that uses a wind turbine to harvest the wind's energy.

Wind Energy Mutual Funds or Wind Energy ETF Exchange Traded Funds are a type of mutual funds or ETF which fall into the Alternative Energy Fund category. Air energy testing would authorize the short-term occupancy of National Forest System lands to determine the feasibility of the site to produce wind energy.

Before Investing in Alternative Energy Stocks, Know the Facts. On the surface, investing in alternative energy funds seems like a great idea, especially since it appears as though this industry will undergo record growth in the coming years.

Green electricity is electricity produced from sources which do not negatively impact upon the earth and its climate. Green electricity is constantly evolving and there are other ways of producing electrical power from green sources. Green electricity is a term describing what is thought to be environmentally friendly sources of electricity.

Wind turbines are available in a variety of sizes, and therefore power ratings. Wind turbines, mounted on a tower at 100 feet (30 meters) or more aboveground can take advantage of the faster and less turbulent wind. Different types of turbines are available for use. Wind turbines produce electricity only when the wind is blowing within the right speed range.

SEP is concerned about the costs of managing the program that are reflected in the Report. The only costs associated with marketing will be those for the travel expenses, telephone, brochures and a website. The high costs and risks of modern warfare are well known and there is a widespread perception that energy problems can best be solved through economic means, not military ones.

Fortunately, it is possible to build efficient DIY wind turbines for the home on your own. DIY home wind energy systems are much cheaper to install and can also be a lot of fun. The financial side of a home wind energy system is very sensitive to the average wind speed in the area, and to a lesser extent, the cost of purchasing electricity.

Wind energy technology can make a significant contribution to the renewable energy supply mix. Wind energy is clean, abundant, and fairly inexpensive, especially when one includes its low environmental costs. Wind energy could provide a significant percentage of our future energy demand.

Wind turbines for the home are clean sources of power that uses a wind turbine to harvest the wind's energy. The spinning turbine converts the wind's kinetic energy into electricity that can then be used in your home. In the meantime, it can be hoped that the building inspectors, zoning boards and planning boards that hear such applications will consider the over-arching objective of encouraging such systems and apply their local ordinances with a reasonable touch.

Use The Renewable Source of Energy to Generate Electric Power and Energy

2012-01-07T21:33:00.000+07:00

Electricity is the most commonly used form of energy and is very essential to people. At present, there are lots of electrical appliances and devices that help people's lives so comfortable and convenient. All of electrical appliances, equipments and gadgets are powered by electricity. Electricity is so important in residential, commercial and industrial structures due to the reason that electricity can be used for illumination, production and many other applications.

There are lots of sources of electricity and the energy resources fall into two main categories namely the renewable source of energy and the non-renewable source of energy. Under the category of renewable source of energy, the commonly used sources are sun, water and wind. While on the non-renewable energy, it can be divided into main types namely fossil fuels and nuclear fossils.

However, due to the issues concerning about the earth's natural sources, the alternative sources to produce electric power is gaining attention from consumers. As people continue to burn gas, oil, coal and earth's rainforest, people are contributing to the increase of global warming. The continuous use of fossil fuels lead to its reduction of supply which is becoming an issue due to the reason that is has reached critical stages. This is why something needs to be done as soon as possible before these non-renewable sources of energy run out.

There are many people who choose to use the renewable source of energy to generate electric power. The materials used for alternative electric energy have already existed and these devices where being modernized and operated with the use of the latest technology. These devices are used in order to produce solar power, wind power and hydropower. These are renewable sources of electricity meaning these sources are pure natural, constant, free and abundant.

Wind power is an alternative electric energy that uses windmills, wind turbine and sails in order to generate electricity. Windmills caught wind in its huge blades causing them to turn. The rotating action turned a shaft and the shaft will turn the millstones. However, today's windmills are now connected to turbines to generate electricity. Another alternative electric energy is the hydropower. Hydropower is generated from water which is being used to turn a wheel connected to a mill. Nowadays, the force of water released from a dam to turn the blades of the turbine connected to a generator produces electricity. And the very popular alternative electric energy is the solar power. Solar energy is an energy derived from the sun and converted into heat or electricity.

Power Energy : The Advantages Gas Electricity Generation

2012-01-07T21:32:00.000+07:00

In the past energy was mostly generated by electric power plants or coals, but now due to many technological, economic and environmental changes, natural gas is now being considered the fuel of choice for gas electricity generation purposes. Gas electricity is a great source of power energy. Due to its burning nature natural GAS has become a very popular fuel for energy generation.

There are many reasons that are persuading people to rely on natural gas for gas electricity production. Also in the presence of coal this is the cheapest fuel that can be used to generate electricity. The reason is that though coal is the cheapest fossil it is also the dirtiest fossil and generates the highest level of dangerous pollutants in the air. In fact, the power generation companies are the most notorious for polluting the environment. Now new regulations to control the power plants from emitting these pollutants have forced the electricity generators to use different methods for gas electricity generation. The availability of new technology has allowed gas to play a very important role in the generation of electricity.

Some of the advantages of Gas electricity generation are:

Among all the fossil fuels available natural gas is the cleanest. Natural gas' main combustion products are water vapor and carbon dioxide. These are the same compounds that we exhale when breathing. In comparison to natural gas the oils and coal are composed of much more complex molecules that contain higher sulphur and nitrogen content. Also a high ratio of carbon; It means that higher level of carbon, sulphur dioxides and other harmful gases are emitted due to the combustion of the oils or coal. All these emissions are really harmful for the health of people exhaling in this environment. In contrast natural gas combustion releases a very small amount of nitrogen and sulphur dioxide and almost no ash.

The green-house effect of global warming is an issue related to the environment that deals with the change in the environment due to increased levels of green-house gases. There are gases in our environment that regulate the amount of heat at the earth's surface level. Scientists believe that an increase in the amount of these green-house gases in the air cause the environment temperature to go up that could result in many environmental effects that can be very dangerous.

Green-house gases consist of water vapors, methane, carbon dioxide, nitrogen oxides and also some engineering chemicals like cholorofluoro carbons. Though most of these mentioned gases occur naturally in the atmosphere, their level is continuing to be increased due to the burning of fossil fuels all over the world. All over the world people are seriously focusing on environmental-related programs. Natural gas is one fossil that is contributing positively to regulate the green-house gases in the environment.

Energy Solar Power : About Solar Rings and How It Works

2012-01-06T14:24:00.000+07:00

You've probably heard all about solar power, and how great it is. You are maybe even tired of hearing about it. But you likely don't yet know about solar rings. Imagine, small rings that hook together and cover the entire surface of your backyard pool.

These rings sit on the surface all day and transfer heat from the sun down to the water below. They're both safe and inexpensive. You can't get trapped under them, they unhook if they are touched.

You can even get a solar powered charger for small electronics like laptops and cell phones. If you have one of these, you won't have to worry about making sure there's an outlet around for plugging in and charging. Believe it or not, you can even find some laptop cases with photovoltaic cells on them that can charge your computer while it is inside the case.

If you are a homeowner, you really should check into a solar powered attic fan. This little beauty only takes a single solar panel, yet it is super effective. The fan cools the attic - which in turn makes the whole house cooler.

An attic fan will help your air conditioner be more efficient. Your AC won't waste energy cooling the attic because it will already be cool. Of course this means your electric bill will drop noticeably.

Solar home systems are just plain efficient and economical. You can do nearly anything with photovoltaic cells.

It costs more at the outset to set up your home with solar power. You have to revamp your electrical system, but you'll recoup the cost in less than ten years. After that it is all pure savings.

Some people object to the panels because they think they are ugly, or worry that the mounts can cause roof leaks. You don't have to reject solar power if you share this opinion. They now have special singles that are designed to look like your roof. They are still as effective, but are inconspicuous.

The APG3014 Portable Generator for Outdoor Environments

2012-01-06T14:20:00.001+07:00

The APG3014 portable generator is a capable 2,000 watt electrical generator that is ideal for use in outdoor environments and in the case of power failures. This unit is a veritable ally when it comes to electricity failure, which is becoming more frequent with severe weather changes around the world. The device weighs roughly 55-60 pounds, and a moderately fit person can lift and move this unit around easily.

Its dimensions are 8.54" long, 14.25" wide, and 15.35" tall. It produces a maximum output of 2,000 watts, while its rated output is 1,400 watts. It can run for 9.5 hours at a 50% load capacity. It features two 11.6 amp 120-volt outlets and one DC 12-volt outlet.

The APG3014 takes unleaded gasoline and SAE 10W-30 oil for its 4-stroke, single cylinder, air-cooled, overhead valve engine. A standard 1-year warranty is supplied with the purchase of this portable generator. This machine is relatively inexpensive and can be found at bargain prices.

The All Power America is quite useful when you want to operate a few tools in the tool shed, go camping, or restore electricity during electrical failures. It is quiet, easy-to-move, compact, and lightweight. It takes surprisingly little gasoline to operate the machine for the majority of the day.

Depending on your appliance's requirements for wattage, the All Power America should provide you with enough juice to run your freezer, television, washing machine, and some lights at the same time. In most cases, appliances with motors require more juice to start than they need to run at sustained levels. For instance, your freezer may need 400 watts to run, but up to 1,000 watts to start. The required level for a motor to start is called the surge wattage.

It might be a good idea to add up the total watts that you plan to utilize with the generator before purchasing. In most cases, you only need to add the surge wattage for the largest appliance. The APG3014 is not an inverter-style unit, which are generally about 3-4 times more expensive than conventional devices. The electricity this unit produces may not be as clean, and shouldn't be used by itself with sensitive electronics.

Consumers can still use the All Power America for sensitive electronics though, provided that they purchase a UL-1449 surge protector. Surge protectors are relatively inexpensive and can be purchased at virtually any market. Consumers can plug the surge protector into the unit and operate sensitive electronics safely.

This generator also has various safety features built-in that ensure that a consumer's investment is protected. If the device ever becomes overloaded during operation, the circuit breaker will shut down automatically. It helps to prevent damage to appliances and the device. The low oil sensor will shut down the device when the oil is too low; this will aid in preserving the engine's integrity.

The Power APG3014 portable generator is a solid choice for consumers who need a compact electrical supply that can operate a fair number of appliances. This device has received many positive reviews. Over 90% of consumers have reported that the machine is remarkably useful in blackouts and powering devices at construction sites, camping grounds, and homes.

The Government Assistance for Solar Power Which Everyone Ought to Know

2012-01-06T14:20:00.000+07:00

Setting up your own solar power generating unit may not be a very cheap option for you. However, it is a great option for the environment. By using solar power you are reducing the pollution that you are producing as well as reducing your carbon footprint. Thus solar helps improve the environment that we live in. This is one of the reasons why governments provide assistance to reduce the cost of solar use.

Why governments benefit from reducing the cost of solar power

There are several countries and states on Earth where power is generated mainly from non-renewable sources such as the burning of fossil fuels. This creates a lot of pollution and harms the environment in a big way. Thus governments are working to reduce this pollution. One of the most effective and cheapest ways to reduce this pollution is to encourage consumers to set up their own renewable power production units by reducing the cost of solar. This takes demand for electricity off the grid and the government has to burn less of the fossil fuels. Along with that if the people start selling the electricity produced back to the government; the need for the burning of fossil fuels reduces even further.

How the government provides assistance to consumers

Governments may provide assistance to the people who are keen in installing solar panels both financially and non-financially. Financial assistance could be in the form of a grant or subsidy that would help the person to set up the solar panel with the minimum initial investment thus reducing the cost of solar power. Along with this the government may also cover the cost of the linking up of the panel to the grid which would save the people a lot of expenditure and would enable them to sell the electricity back to the grid. To help set up the power unit the government may also provide a discount on the components of the solar system such as panels and installation equipment such as rails. All of these methods help in bringing down the cost of solar substantially for consumers.

The government may also provide non-financial benefits to the people which can be in several forms. It may help to reduce the cost of solar power by providing consultation services to those interested at no fee. The consultants would help bring the cost of solar power down substantially for the individual interested families.

Not all governments provide assistance for solar power

Although most governments have incentives to help reduce the cost of solar power for individual households, there are also some governments that would not find this useful. The reason for this is that some governments produce all of their electricity from renewable sources such as from geothermal energy, wind power and solar power. Thus these governments would not be especially keen on getting solar panels installed in individual homes. However, if there is a shortage of electrical power in the area, the government may still assist the people in bringing down the cost of solar power which would help the households without affordable power and high electrical bills.

The Greatest of Using The Internet Intended for Looking at The Assistance Provided by Electrical Power Corporations

2012-01-03T10:28:00.000+07:00

Guidebook comparison shopping for electricity price ranges is not something that anyone appears to be toward. In fact, it needs a number of strenuous time associated with speaking to the product sales associates of several utility companies on the phone or perhaps person, a long time that can have been offer better work with. However, creating side by side comparisons between energy businesses is an extremely critical task and now we is now able to luckily assess strength costs online.

The greatest advantage of using the Internet intended for looking at the assistance provided by these kinds of electrical power corporations is it is actually quickly, simple and handy. It is possible to go browsing the Internet at any time you desire and you can visit the web site of those electrical energy as well as petrol companies to compare and contrast what they’ve to provide.

Considering the fact that the marketplace for gasoline and isn’t a secure marketplace, comparison shopping for strength charges can be an activity that you have to attain at any rate. Luckily, this arena can be leveled by the fact that just about all electricity companies in england belong to a similar list of govt polices. You will get the most effective company that you might want for ones power as well as propane desires, whether or not the company is usually a new gambler available in the market or perhaps an outdated palm.

Whilst a person evaluate the assistance of most of these person power vendors plus the expense of their own products and services, you need to be aware about a couple critical factors, specifically given contract deals as well as marketing promotions. If you’ve found yourself prescribed a maximum contract deals with regard to power products and services, it can imply that the you will pay are generally constant for many decades irrespective of no matter what happens within the electricity market place. Capped data plans will give you a huge advantage if you plan to adhere to a single energy company for several years.

The other retains for anyone who is only contemplating appealing the power firm’s providers momentarily. Uncapped contract price discounts may well necessarily mean a lot more financial savings to you personally because you be able to spend less while strength price ranges go down out there. You just need to look and see the market industry carefully.

On the subject of personal savings, this promotions supplied by strength organizations in order to potential customers may also save some bucks. Your competitors in perfect shape in britain vitality market, on account of the visibility in the market. Other sellers provides yanked lower fuel costs and also energy creation expenses with regard to buyers. Due to levels of competition, you can definitely have the strength providers you might need since inexpensively as it can be. This is where surfing the Internet to compare strength price ranges gets to be beneficial. You’ll be able to seek out the cheapest deals that you can come across along with savings. It’ll only take a little bit of bit of to seek out these types of specials that suit your requirements very best.

The online world is certainly handy low-priced energy price ranges. That gives you entry to the market in addition to discover the particular manufacturers for whatever stuff that you need. Shopping around on the Internet is absolutely much simpler and also practical since entry changes whenever they are presented. You are likewise guaranteed to receive the best deals and also pick up by far the most personal savings when you compare vitality rates on the web.

Peak Orderly Power Supply Plan Will Give Priority to The Residents of Electricity

2012-01-03T10:27:00.000+07:00

“The national electric power supply and demand nervous. In power load up, power generation gap increases, the proportion of electricity by increased, in Beijing this summer will also be the power supply and demand contradiction.” Beijing electric power company spokesman, said Beijing is expected to power grid zhao4 yun2 this summer in electrical load biggest 18.5 million kw to 19.1 million kw, a 2010 growth between 11.04% to 14.64%, among them, air conditioning cooling load account for 40%.

Beijing is typical of the power grid, by more than 78% of the electric power resource to other provinces and cities, therefore, in conveying the external power supply shortage or extremely bad weather condition, Beijing power grid will face the problem of power supply gap.

At this summer’s overall power gap and local area in the weak link, the electric company compiled the orderly power supply management scheme and pull way limiting power ordinal measures, the city government has already been reported by the relevant department for examination and approval. Zhao4 yun2 disclosed.

If appear continues the high temperature high humidity and extreme weather, or destruction of external force in the accident, and the relevant department damaged power supply facilities will carry out the wrong peak, peak orderly power solutions and pull way limiting power measures. But, and residents will be priority is making sure “electricity.

The Northwest into the the weak link

The summer heat, electricity use surge, residents in Beijing rising power load, the most serious substation overload-white fang changping district 110 kv substations but it can no longer bright red flags.

The substation responsible for more than residents in 30 connects center provide electricity security. Last summer, the continuous wet high temperature weather, residents in white fang, electricity substation overload, equipment for high temperature operation serious 2 hours 28 minutes, had become a Beijing area overload serious one of transformer substation.

“This year won’t appear of last year, connects center area power supply can worry about.” Changping power supply company director of technology production Xiao Wan Fang said with a laugh. White fang substation after modification, the substation capacity to 150 million current-voltage, power supply has increased 138%.

According to information, the Beijing municipal power company new and expansion this year of 110 kv substations and above 20 seats, the project implementation greatly alleviate the light, connects center, shangdi, grass bridge in the provinces of power supply pressure, basic satisfy these areas the growth of power demand.

However, Beijing power grid still has some concerns. “Due to the power grid construction influence, the northwestern Beijing area by insufficient power allocation, this also is Beijing power grid in the network structure the weakest link in this summer, the power supply situation.” Zhao4 yun2 said.

Electricity saving should start to reduce standby

“Beijing in surrounding areas for support and, at the same time, to start from me, save electricity reasonable of electricity.” Beijing municipal development and reform commission officials say. Last summer, Beijing clearly requires public institutions and develop power saving of the first demonstration role. Strict control indoor temperature, air conditioning room temperature shall not be lower than the summer set and 26 degrees Celsius, advocating set to 27 degrees Celsius.

For the average household saving electricity, experts court, residents are not at home, should turn off the electric equipment switch, reducing standby power consumption. Also, try to avoid more powerful electric appliance and at the same time, to ensure safety.

Advantages and Disadvantages of Option Energy Source

2012-01-03T10:26:00.000+07:00

Because of growing global power consumption as well as the probable depletion using the world’s non-renewable energy source, ways of exploring and utilizing renewable power sources are being undertaken. Using alternative energy source could be both beneficial and challenging. Why don’t we explore the numerous advantages and disadvantages of alternative energy source. A substantial benefit of renewable power is it’s renewable therefore it is sustainable and can by no means go out. More to the point option power produces little or no waste material that could pollute or has harmful effects around the environment. Some countries using renewable power as the second method to obtain power will also be showing some economic benefits especially in many regional areas. The majority of their projects are situated away from the urban centres and capital cities. These folks were able to improve the use of nearby services together with tourism. Common downside of utilizing alternative power is it is hard to create big volumes of electricity comparable to that relating to conventional standard fuels. An additional prevalent problem amongst renewable power sources will be the reliability of the power supply. Since it is naturally generated, alternative power supply makes use of the next thunderstorm condition.An additional drawback or drawback to renewable energy source is that it’s comparatively more costly to create the gear necessary for producing the energy.

Listed here are the number of advantages and disadvantages of option energy source.

1. Solar Power

The sun’s rays is a superb supply of power as it’s totally free and is effective. It is feasible to maximize the energy given by sunlight to exchange conventional electricity. But you’ll find limitations, like areas at high latitude and locations with frequent rains are places unable of producing effective solar power.

2. Wind Energy

Wind can be an effective electricity source. It’ll be feasible that wind power can replace as a lot as 20 percent using the total electric consumption in the foreseeable future. It’s also a really environment-safe supply of energy because there are no dangerous gases stated within the operation of converting the power. Location is a very important aspect in utilizing wind energy, high latitudes and coast lines are great locations to set up windmills. A relatively large land area is also required to set up adequate number of windmills.

3. Hydroelectric and Tidal Power

Each this energy originates from water. With hydroelectric power it truly is primarily sourced from dams. Tidal energy, alternatively, utilizes natural tides using the ocean. Manufacture of power from water is an additional clean way of producing power. However there are many disadvantages. Setting up river dams as reasons for hydroelectric energy is very costly, while tidal source of power depends a lot sailing. Since oceans tend to unpredictable you are able to find only 9 locations worldwide that are suitable for this kind of energy source. And tidal energy energy vegetation is also believed to offer side effects on the migratory birds and also the fishes.

4. Biomass

Biomass consists of fermented animal waste, agricultural crops, grains also as other natural products. It could be used to make an alcohol and also replace gasoline requirements. It maximizes waste materials alternatively power source. A drawback, it that it still produces greenhouse gas.

LED Lights Offer Exceptional Energy Efficiency

2011-12-01T00:02:00.004+07:00

In recent years, energy efficiency has become a hot topic, and more and more people are looking for ways to make their homes as efficient as possible. But did you realize that one little change of a lightbulb can dramatically impact your house's energy efficiency and reduce your overall energy costs? By switching to CFL lightbulbs, or better yet LEDs, you can save a bundle.

Why Install LED Lights?

There are basically only two reasons to install LEDs for your lighting needs, but they can be powerful motivators. These reasons are long life and energy savings. As a much more energy-efficient lighting source, LEDs can help keep your electricity costs low while still keeping the lights on.

Here's how the three main types of lightbulbs break down:

Incandescent Bulbs: Popularized by Thomas Edison, this type of lightbulb is what most people think of when the term "lightbulb" is mentioned, and most older lamps are designed to utilize this technology. However, because approximately 98% of the power consumed by an incandescent bulb is wasted as heat rather than light, these lights are extremely inefficient. Many countries have completely phased them out.

Compact Fluorescent Lightbulbs (CFLs): According to the federal Energy Star program, CFLs last up to 10 times longer than a typical incandescent lightbulb and use around 75% less energy (although they still emit 80% of the power consumed as heat rather than light). Popular because they are more efficient than traditional incandescent bulbs, CFLs do have the drawback of being around four times more expensive than a standard incandescent. However, in most applications, these fluorescent lights pay for themselves in reduced energy usage in less than six months. Each CFL bulb can eventually save consumers around $40 over the course of its life. Some environmental activists have expressed concern regarding the mercury content of CFL bulbs, although there is little-to-no health risk associated with unbroken CFL lights.

Light-Emitting Diodes (LEDs): LEDs are a type of light called a solid-state light, and they emit almost no heat when in use, making them much more efficient light sources. LED lights can last 60,000 hours or more, resulting in a standard life span of between 10 and 15 years. Compared with the already substantial useful life of a CFL, LEDs last another 10 times longer. However, LED lightbulbs are extremely expensive. Their prices have fallen dramatically in recent years, down to around $40 from $100, but that's still a lot of money to shell out for just one lightbulb. On the other hand, LED bulbs use just a fraction of the energy of incandescent lightbulbs and CFLs. For example, to get the same amount of light, you'd need a 100 watt incandescent bulb, a 26 watt CFL, or a LED of just 10-15 watts. In terms of energy used, the long-term savings is extraordinary.

The short of it is that LED lights are expensive up front, but with a life span of more than a decade and decreased energy usage of up to 90% over a standard incandescent lightbulb (100 watt), you will enjoy extensive savings over time.

How to Install LED Lighting

Until recently, you only had one option when it came to installing LED lighting: replacing all your light fixtures with models specifically designed to work with LED lights. Because the vast majority of all LED lightbulbs featured a pin, or "plug-in," base, they could only work with specialty LED lights. However, current attitudes toward energy efficiency have motivated the development of LED bulbs that can fit into traditional light fixtures. That means that upgrading to energy-saving LED lighting for your home is as simple as purchasing LED bulbs equipped with standard screw-in bases. Available in a variety of shapes and sizes ranging from small reading lamps to flood lights, LED lighting now works with many existing light fixtures.

If you're still interested in switching out some of your old light fixtures to better suit your current needs or to accommodate plug-in LED bulbs, an electrician in your local area should be able to provide assistance. Not all residential electricians provide LED lighting upgrades, so make sure that the electrical contractor you hire is qualified to handle the project.

Remake Your Outdoor Space With Landscape Lighting Design

2011-12-01T00:02:00.003+07:00

Get expert assistance from a qualified electrician when you're updating your outdoor space. From landscape lighting to swimming pool wiring installation, having the right electrical contractors on your team can make a world of difference!

When you want to establish a beautiful outside space, having the right electrical components at your disposal can make all the difference. From solar powered landscape lighting to underwater pool lights, electricians who specialize in exterior electrical work can help you achieve the perfect look for your property.

Not all electricians will be able to tackle outdoor jobs, so when you're serious about making your outside space livable, functional, and beautiful, call a professional who offers specific outdoor electrical services. These electrical contractors will survey the areas in question, talk with you about what you want, and design the right lighting or wiring scheme to achieve your ideal outdoor space. With all of the necessary experience and tools at their disposal, these experts in landscaping lighting and other outdoor electrical needs will be able to tackle whatever project you have in mind.

Outdoor landscape lighting is, in fact, one of the most common projects that exterior electrical experts undertake. With beautiful lighting fixtures configured as part of a cohesive design throughout your outside space, you can enjoy the expanse and beauty of your garden or yard throughout the evening, no matter how dark it gets. Your outdoor lighting specialist can install this type of system with only minimal disturbance to the space. You won't have to dig up all your plantings or sacrifice your garden to workmen for weeks to install these features. Your electrician will have the tools and experience to put in the lighting that you want quickly and in the least invasive manner. The result will be a stunning lighting scheme that will increase the overall beauty of your property and will allow you to see, enjoy, and use your outdoor space at any time of day or night.

Swimming pool wiring is another job frequently undertaken by outdoor electrical contractor specialists. The combination of water and electricity makes this a particularly dangerous line of work, and one that you should certainly leave to the professionals. With swimming pools, there's more in play than just the lights in terms of electrical components. There are also filtration and circulation systems to be taken into account, which, along with the lighting, help keep a pool functional, pleasant, and attractive. Whether you want dramatic lighting to emphasize the pool as a feature of your property, or you just want the basics in place for the sake of aesthetics and safety, electrical professionals will work with you to design the appropriate pool wiring for your property and will install it so that you can enjoy a clean, well-lit pool all summer long.

Outdoor electrical work deals with the same elements as interior work, but in terms of design and successful execution, it calls for an expert to really do the job well. When you work with an electrician who specializes in exterior projects, you'll know that your landscape lighting or swimming pool wiring has been designed and installed with an eye to beauty, quality, functionality, and safety.

The Duties and Responsibilities

2011-12-01T00:02:00.002+07:00

It is important that electrical installation work is carried out by trained and qualified electricians who have the necessary knowledge, skill and experience. The internet is the new Yellow Pages. But how do you know which company to choose and what services you require?

The answer, probably, is that you don't. If you "Google" for an electrician in your area you are guaranteed to have pages and pages of results. So which one do you use? The one with the better looking website - or the one that is just down the road?

You can form an opinion of who to use based on the information provided on the website and here are some things to look out for

1) Clear, concise and relevant information on the site

A website with very little information could show that the company/individual doesn't know their field of expertise and a website with too much information or one that bamboozles you with technical jargon could also indicate that there is no understanding behind the theory. A good website should give you an overview of services offered and some detail on the chosen service.

2) Registration with a governing independent voluntary body

Any company registered with one of these schemes will have had samples of their work checked to ensure it complies with BS 7671 and to ensure that they have the knowledge and expertise to carry out electrical work. Part P (domestic dwellings)registration with any of these companies is a less rigorous compliance procedure than full approval status, this is not to say that any company/individual who is Part P registered is less able to do their job but that there may be limitations to their electrical scope of work

3) Qualified electricians working for the company you choose, electrician's should work to the latest regulations (BS 7671 2008 17th edition wiring regulations) and should have received relevant training.

Before choosing who to use you should ask the company for a quotation, for small works an over the phone quotations may suffice but for larger works you should ask a detailed written quotation. At the appointment you can get to know the company on a better level.

Look out for the following things:

1) Smart, clean & professional image including van and company employee

2) Electrical knowledge

Does the person who is speaking to you understand what you are asking? Have they been able to comprehend what you would like to be done and if appropriate make alternative suggestions over the work or fittings?

3) Any new electric work carried out at the property must be carried out to the current regulations

This can mean that work may have to be carried out to the existing installation to ensure compliance and safety. It is sometimes advisable to upgrade your existing electrics at the same time as having additional wok carried out as this may well be a more cost effective option than carrying out the works and upgrading at a later date. Has the electrician provided you with information regarding the current electrical wiring in your home? Many people are worried that this means the electrician is trying to gain more work but in fact any professional qualified electrician is under obligation to tell you if something is not right, and if they don't, do they really know what they are talking about?

4) Is the quotation verbal or written; is it handwritten or computer generated?

You should always obtain a written quotation for works and ensure that you understand any limitations of the quotation

Once you have received the quotation if you have any questions then ask. It is important that you understand the quotation and if you need to call the electrician then do, they won't mind.

Once you have the quotations and are happy with the companies then next thing you will probably look at is price, but be warned cheapest is not always best. Being an electrician is a skilled job, after all you wouldn't let any Tom, Dick or Harry fix your car because they said they knew what they were doing and it was cheaper would you? So don't do the same with the electrics in your house - electricity can and does kill and it could only take one electrical problem to cause an electric shock or a fire.

Unsure of who to choose at this stage - then ask for references. Speak to the people, who the electrician has worked for in the past, or visit the site and view a completed project. There is a possibility that the internet information is self-populating, and that the electrician (or company) has got his mates to refer him/his business as a good service provider.

And finally, once the work has been completed (and in certain cases the relevant certificate has been issued) let other people know who you have used so they can be sure of using a skilled, ethical and experience electrician themselves.

Modified Sine Wave Inverter To Take Electricity With Different Types and Function

2011-11-17T10:40:00.000+07:00

We live in a society fueled by electricity, and spending just a day without electricity could have serious hurdles for most of us. When we head out onto the road, into the wilderness, or anywhere else that lacks the familiar wall outlets of our home, we're essentially leaving behind some of our modern comforts. But a power inverter can let you add those well-loved AC outlets to anywhere you might be, whether you're afloat in your boat on the sea, relaxing at a campsite, or speeding across one of the nation's highways. In short, a modified sine wave inverter lets you take electricity with you.

A power inverter works by converting the DC charge in a battery into AC energy that you can use for other applications. You'll be able to plug your electronic devices into a standard outlet, and a good power inverter will also feature a USB port for charging up your favorite gadgets and gizmos. The inverters are sold according to their wattage capacity and the larger the wattage the more items or larger sized items it can handle. To figure out your wattage needs you need only multiply your items' total combine amperage needs by 120. This gives you the overall watts your modified sine wave inverter will need.

A power inverter is different from a pure sine converter because of the signal clarity it delivers. Using a modified inverter will create a less stable current that features spikes and dips in the signal. This can cause some sensitive equipment to work improperly or not at all, which is why those with very specific needs will likely want to consider a true sine wave unit. But a modified sine wave inverter is much cheaper than its counterpart and is usually all that most people require to run most of the devices they plan on using with it.

If you're looking for a way to add a radio to your campsite or keep the kids happy on a long drive, a power inverter is the certainly the best way to go about doing so. You'll be able to find a modified sine wave inverter with a wattage requirement of whatever you might require, and the smallest units are so portable and lightweight they can plug directly into your car's cigarette lighter. From one hundred watts to eight thousand, a power inverter is the best way to take electricity with you wherever you roam.

The Perfect Solution for Electricity Supply Problems

2011-11-17T10:37:00.005+07:00

Power outages are a fact of life, and this problem is especially poignant for people who live in more isolated areas, or if your local electricity grid is undergoing renovation. Many people need a constant supply of power for home operations, and power downtime can be a real problem if these operations are sensitive and suffer from such downtime. Not only that, but the general nuisance of fumbling around in the dark for other sources of light, and not being able to do anything that requires power can become extreme if your area is susceptible to power outages. If you are fed up of power outages affecting you, or if you need to ensure reliable power 24/7, then a home generator may be the perfect investment for you, and this article will clarify what there is available.

Home Generators Explained

A generator generates electricity by the conversion of mechanical to electrical energy, whereby the movement of the generator creates the flow of electrons in an external circuit. This general principle is exploited by the major energy suppliers to give households electricity. Conversely, a generator for home use can be used to do the same thing, and this makes them ideal for replacing the traditional power supply when power outages occur.

Generators can vary in price, depending on their performance, model and power output, and vary from cheap generators to expensive ones. There are two main kinds of generator, namely portable generators and standby generators.

Portable Generators

These are the most common generator available to buy, as they are well priced and can be used for home use, and are light enough to take with you on camping holidays, for that extra convenience and security. These generators run on gas like propane or diesel, and standard cheap generators will supply the usual 120 volts. Appliances can be directly connected via a transfer switch.

Standby Generators

These are larger, more expensive versions of portable generators, but the extra price has a reason; these can be used to power your entire household in the event of a power outage. They are installed in a permanent place in your home, and can be directly wired into your home's mains, and directly wired into your gas supply, or have its own supply. They are clever home generator, and can be made to step in automatically to provide electricity once it detects a power outage.

Things to Consider When Buying a Residential Standby Generator

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Residential Standby Generators serve two purposes; automatically starting in the event of a power outage and delivering essential electrical power to designated appliances, rooms, tools, and devices. There are several issues to consider when the decision comes down to choosing a residential standby generator versus a portable unit. They are:

1. The biggest difference between these types of generators from portable units, besides mobility, is that residential standby generators are generally designed to remain connected to the home's circuitry through the main electric panel. This allows for a generator to power up either automatically, via an automatic transfer switch, or by push button at the onset of a power outage. A portable unit, on the other hand, could require fueling, a rollout from storage, and connection to the home's circuitry. For a residential standby generator, an automatic switch to generated power normally takes between ten to thirty seconds. A push button start takes about the same time once the generator has been turned on. An added advantage to a residential standby generator is that the addition of a USB battery accessory can ensure that power remains on during the changeover to generated power. This is essential for a range of uses ranging from preserving data on a computer to delivering uninterrupted power to an at-home medical device.

2. Advances in portable power generation have increased power output levels to the point where power delivery can rival the smaller residential standby generators. Still, depending on power requirements and other factors, going with a stationary generator can be the logical choice. Here, there are two considerations, the first one being the power requirements for appliances, rooms, and devices which must remain on during an outage. Refrigerators and air conditioners, for example, require heavy wattage for both startup and running time. The addition of other power needs can easily mandate the higher power output of a residential standby generator. The second consideration is whether a generator which meets the needs of the home can easily be moved into place in the event of an outage. The weight of the unit, severity of local weather, and the difficulty of moving a portable from storage to the main electrical panel must be taken into account.

3. Another consideration is the expected run time of the generator. Smaller portable generators, for example, have run times at full capacity of approximately four hours. In an extended outage, a portable could require refueling several times. Under a variety of circumstances, this may not be an option. Residential standby generators, conversely, can be connected to a natural gas line, allowing for run times as long as power remains down and eliminating the need to refuel.

How Solar Power Inverter Works

2011-11-17T10:37:00.003+07:00

The public has shown a heightened interest recently in the possibilities of solar power and all that it can do for the environment, as the looming energy crisis casts a shadow over our daily use of energy. Because of this, more and more solar panels are being installed onto rooftops all over the world, with government funds helping assist with the education and research of this exciting energy source. Solar energy panels can power a whole home with electricity in a renewable and sustainable way, but may require the use of a solar power inverter as well to provide the most energy capabilities.

A solar power inverter works by changing a direct electrical current to an alternating current, using a whole process of electrical switching. The process is not that complicated, but there are three main different styles of solar power inverters that work in slightly different ways, including the stand-alone solar panel inverter, the synchronous solar panel inverter, and the multi-function solar panel inverters. The first type switches direct current, or DC power from a battery over to an alternating current, or AC. This provides enough power for small personal appliances, including computers; or enough to supply the whole household if desired.

The second type of solar power inverter is the synchronous type, which allows the household to work with the power company. When energy is collected into your solar panels and then stored in a rechargeable battery, if you end up not using all of the energy that is stored there you can sell it back to your utility company, rather than having the power go to waste. This is helpful for those household who don't want to have to calculate how much AC power they plan on using throughout the month, and allows you to store an emergency amount. Additionally, with this type if it appears that the solar panels you have are not producing enough energy, the power company can compensate for the difference.

Finally, there are multifunction solar power inverters that deal with both modified sine waves and true sine waves. These also convert the DC power to AC power, but on a more delicate level, allowing you both to store up energy that is collected by the solar panels, and pass it along throughout the household. Because these are suitable for a wide range of potential household needs, they are generally considered by experts to be some of the most useful.

Wind Turbines For The Home

2011-11-17T10:36:00.000+07:00

The high costs and risks of modern warfare are well known and there is a widespread perception that energy problems can best be solved through economic means, not military ones.

The financial side of a home wind energy system is very sensitive to the average wind speed in the area, and to a lesser extent, the cost of purchasing electricity.

The Unit of Energy Measurement

2011-11-12T13:14:00.001+07:00

The most common unit of measurement on the electricity meter is the kilowatt hour (KWh), which is equal to the amount of energy used by a load of one kilowatt over a period of one hour, or 3,600,000 joules. Some electricity companies use the SI megajoule instead.

Demand is normally measured in watts, but averaged over a period, most often a quarter or half hour.

Reactive power is measured in "thousands of volt-ampere reactive-hours", (kvarh). By convention, a "lagging" or inductive load, such as a motor, will have positive reactive power. A "leading", or capacitive load, will have negative reactive power.

Volt-amperes measures all power passed through a distribution network, including reactive and actual. This is equal to the product of root-mean-square volts and amperes.

Distortion of the electric current by loads is measured in several ways. Power factor is the ratio of resistive (or real power) to volt-amperes. A capacitive load has a leading power factor, and an inductive load has a lagging power factor. A purely resistive load (such as a filament lamp, heater or kettle) exhibits a power factor of 1. Current harmonics are a measure of distortion of the wave form. For example, electronic loads such as computer power supplies draw their current at the voltage peak to fill their internal storage elements. This can lead to a significant voltage drop near the supply voltage peak which shows as a flattening of the voltage waveform. This flattening causes odd harmonics which are not permissible if they exceed specific limits, as they are not only wasteful, but may interfere with the operation of other equipment.

In addition to metering based on the amount of energy used, other types of metering are available.

Meters which measured the amount of charge (coulombs) used, known as ampere-hour meters, were used in the early days of electrification. These were dependent upon the supply voltage remaining constant for accurate measurement of energy usage, which was not a likely circumstance with most supplies.

Some meters measured only the length of time for which charge flowed, with no measurement of the magnitude of voltage or current being made. These were only suited for constant-load applications. Neither type is likely to be used today.

Types of Meters

Mechanism of electromechanical induction meter.

1 - Voltage coil - many turns of fine wire encased in plastic, connected in parallel with load.

2 - Current coil - three turns of thick wire, connected in series with load.

3 - Stator - concentrates and confines magnetic field.

4 - Aluminum rotor disc.

5 - rotor brake magnets.

6 - spindle with worm gear.

7 - display dials - note that the 1/10, 10 and 1000 dials rotate clockwise while the 1, 100 and 10000 dials rotate counter-clockwise.

Electricity meters operate by continuously measuring the instantaneous voltage (volts) and current (amperes) and finding the product of these to give instantaneous electrical power (watts) which is then integrated against time to give energy used (joules, kilowatt-hours etc.). Meters for smaller services (such as small residential customers) can be connected directly in-line between source and customer. For larger loads, more than about 200 ampere of load, current transformers are used, so that the meter can be located other than in line with the service conductors. The meters fall into two basic categories, electromechanical and electronic.

Electromechanical Meters

The most common type of electricity meter is the electromechanical induction watt-hour meter.

The electromechanical induction meter operates by counting the revolutions of an aluminium disc which is made to rotate at a speed proportional to the power. The number of revolutions is thus proportional to the energy usage. It consumes a small amount of power, typically around 2 watts.

The metallic disc is acted upon by two coils. One coil is connected in such a way that it produces a magnetic flux in proportion to the voltage and the other produces a magnetic flux in proportion to the current. The field of the voltage coil is delayed by 90 degrees using a lag coil. This produces eddy currents in the disc and the effect is such that a force is exerted on the disc in proportion to the product of the instantaneous current and voltage. A permanent magnet exerts an opposing force proportional to the speed of rotation of the disc. The equilibrium between these two opposing forces results in the disc rotating at a speed proportional to the power being used. The disc drives a register mechanism which integrates the speed of the disc over time by counting revolutions, much like the odometer in a car, in order to render a measurement of the total energy used over a period of time.

The type of meter described above is used on a single-phase AC supply. Different phase configurations use additional voltage and current coils.

The aluminum disc is supported by a spindle which has a worm gear which drives the register. The register is a series of dials which record the amount of energy used. The dials may be of the cyclometer type, an odometer-like display that is easy to read where for each dial a single digit is shown through a window in the face of the meter, or of the pointer type where a pointer indicates each digit. With the dial pointer type, adjacent pointers generally rotate in opposite directions due to the gearing mechanism.

The amount of energy represented by one revolution of the disc is denoted by the symbol Kh which is given in units of watt-hours per revolution. Using the value of Kh, one can determine their power consumption at any given time by timing the disc with a stopwatch. If the time in seconds taken by the disc to complete one revolution is t, then the power in watts is:

For example, if Kh = 7.2, and one revolution took place in 14.4 seconds, the power is 1800 watts. This method can be used to determine the power consumption of household devices by switching them on one by one.

Most domestic electricity meters must be read manually, whether by a representative of the power company or by the customer. Where the customer reads the meter, the reading may be supplied to the power company by telephone, post or over the internet. The electricity company will normally require a visit by a company representative at least annually in order to verify customer-supplied readings and to make a basic safety check of the meter.

In an induction type meter, creep is a phenomenon that can adversely affect accuracy, that occurs when the meter disc rotates continuously with potential applied and the load terminals open circuited. A test for error due to creep is called a creep test.

Electronic Meters

Electronic meters display the energy used on an LCD or LED display, and can also transmit readings to remote places. In addition to measuring energy used, electronic meters can also record other parameters of the load and supply such as maximum demand, power factor and reactive power used etc. They can also support time-of-day billing, for example, recording the amount of energy used during on-peak and off-peak hours.