Pacific Crest Transformers

The Role of Harmonics and Non-Sinusoidal Loads in a Wind Farm

Wind turbine transformers should be designed for the additional heating caused by harmonic loading and have an electrostatic shield between windings, neither of which are provided by conventional "off the shelf" transformer designs. Read on for more information on the role harmonics play in wind farm transformer design. Harmonics Basics Transformer design is based on the principal of creating a fluctuating magnetic field from a uniform sinusoidal input alternating voltage source to induce current flow in, and voltage potential across, an electrically separate conductor in that fluctuating field. A purely uniform sinusoidal wave form is possible only theoretically. In real world transmission and distribution power systems, voltage and current waves get distorted from the ideal. In fact, total harmonic distortion (THD) of 1 to 2 percent is common at the point of generation. Also, non-linear loads such as switching actions, rotating machinery, variable frequency drives, and electronic devices of all types add further distortion to the ideal wave shape. The cumulative distortions repeat every cycle, adding peaks that ride on the voltage and current waves and occur at other than the fundamental frequency of 60 Hertz. The harmonics creating these distortions are multiples of the fundamental frequency and are referred to by their multiple, for example, 3rd, 5th, and 7th. Dangers of Harmonics The danger from harmonics is that they increase the eddy and stray losses within the transformer. Eddy and circulating currents in a winding conductor causes additional heating which must be addressed with additional cooling. Otherwise, the additional heat can cause insulation degradation and lead to premature transformer failure. Harmonics in Wind Turbine Generators Wind turbine generators, like conventional generation sources, will produce generator-caused distortions, which result in harmonic wave forms. In addition to these harmonics caused by the generators, the turbine step-up transformers are managed with solid state controls that contribute their own form of damaging harmonics. Rectifier/Chopper Circuits Generator systems using rectifier/chopper circuits present particular problems for the transformer. Since harmonic losses for this configuration are multiples of the transformer's inherent winding eddy current losses, design steps are required to reduce the eddy losses to compensate for the harmonic currents. For rectifier/chopper turbine controllers, the transformers should be designed for harmonics similar to those for furnace or rectifier transformer applications. If not addressed by the transformer designer, the combined non-sinusoidal wave forms from the turbines and the switching induced harmonic wave forms will create excessive heating in the transformer. Shortened life spans and premature failures can result from using conventional distribution transformers which are not designed for this type of duty Harmonics contributed by rectifier/chopper type controllers contain high frequencies that can also affect other equipment on the grid if permitted to pass through the transformer. One example is that protective equipment may see this as a fault condition and attempt to disconnect the turbine. Though harmonic filtering is not specifically a function of the turbine step-up transformer, electrostatic shields located between the primary and secondary windings will act as a filter to prevent the transfer of dangerous harmonics onto the collector bus. Thus, an electrostatic shield should be considered mandatory for a turbine step-up transformer.

Switching Surges and Transient Over-Voltages in Wind Farms

The long cable runs and frequent switching operations found in multi-tower wind farms puts the wind turbine step-up transformer at greater risk than a conventional distribution or power transformer installations. Carefully locating the wind farm, along with using transformers with fault ride through capability, grounding transformers, surge arrestors, and properly rated transformer bushings, are among the strategies that can be used to counter the risks from switching surges and over-voltages at wind farms. Locating Transformers at Wind Farms The general rule of thumb for locating a transformer is to reduce the costs of large copper cables by placing the transformer in a manner that reduces the length of low voltage, high current cables. When this consideration is applied to wind farms, it follows that the wind generator and its associated transformer should be as close together as possible. For land based sites, the turbine step-up transformer can either be located as near to the tower base as possible, or alternately, within the tower or nacelle. For off shore sites, the latter is the only realistic choice available. It should be noted that while liquid filled pad-mounted transformers are the normal for location adjacent to the turbine tower, dry-type transformers are normally used for nacelle mounted transformers. Of course, the placement of the transformer is decided by the construction of the wind generator manufacturer. The problem with large sprawling turbine arrays is that the need for connecting the individual turbine step-up transformers to the "collector" bus results in very long cable runs. This in turn results in increased voltage drops, cable related resistive and capacitive losses, and the increased potential for cable ground faults. The extensive use of cable in wind farms coupled with their "daisy chain" connection pattern leads to two primary systems problems: cable faults and voltage stress caused by single or double line-to-ground fault. Cable Faults A radial wind farm configuration typically connects ten to twelve transformers in a daisy chain fashion. The pad-mount transformers are configured with a loop-feed bushing arrangement, in which the transformer at the end of the radial line is connected to the next transformer in line. The second transformer from the end is connected to the third and so forth until the first transformer in line is connected to the collector bus. Since a cable fault can happen anywhere along this radial line, the transformer must be able to handle fault currents from a fault at any location The fault ride through requirement becomes critical, since clearing a fault would require disconnecting a complete radial line, approximately 20 to 30 MVA of generation. Single or Double Line-To-Ground Fault Voltage Stress In addition to the fault currents that occur during a fault, a single or double line-to-ground fault causes voltage stress on the transformer. A single phase cable fault, on the Delta-connected HV winding, causes one phase to ground, putting phase-to-phase voltage between the other two phases and ground. The resulting voltages overstress the transformer's insulation system. Finding and clearing the cable fault is exacerbated by the longer cable runs and the wind farm layout. The use of grounding transformers at critical locations within the wind farm helps alleviate this type of dielectric stress. The grounding transformer provides a zero sequence impedance to support the voltage on a faulted leg during a single line-to-ground fault. By holding the faulted phase above ground, this impedance acts to limit the resulting overvoltage on the un-faulted phases. Most grounding transformers have a thermal fault rating in the range of 10 seconds to one minute. This may give an indication of the expected length of a fault. Fault duty due to either voltage or current are serious concerns that need to be addressed by both the wind farm developer and the transformer manufacturer. Increased Lightning Exposure and Voltage Surges from Repeated Switching Further concerns for the reliability of the turbine step-up transformer center on the increased exposure to lightning strikes and transient voltage surges resulting from the repeated switching. Wind farms are located in remote areas, typically at higher elevations or exposed plains, where wind patterns are unobstructed by surrounding terrain and man-made or natural obstacles. Unfortunately, this increases the transformer exposure to storm events and lightning strikes, especially considering the geometry of the turbine and tower combination. Surge arresters should figure prominently in the wind turbine step-up transformer protective equipment list. Perhaps an even greater concern is transient over-voltages cause by switching. Changes in wind strength are directly translated into a varying load profile for the step-up transformer. As the wind speed increases, the turbines are brought on line. When the wind strength begins to wane, the loading drops and ultimately the turbine is switched off line. This can happen multiple times within a 24-hour period as surface wind is affected by diurnal heating cycles or incoming weather patterns. It can also happen when a feeder breaker opens and disconnects the turbine step-up radial line from the collector circuit. Breaker operations introduce a transient recovery voltage (TRV) wave into the wind turbine step-up transformer voltage circuit. This phenomenon is exacerbated by the present day extensive use of vacuum breakers and their extremely rapid switching times. The TRV surges associated with breaker switching operations on either the HV or LV side of the transformer can combine with cable capacitance and produce standing waves and ringing that are many times the original voltage levels. These extreme voltages can lead to transformer dielectric failures. When the frequency content of the high voltage, fast rise-time, TRV surges coincide with the internal resonant frequencies of the winding, the circuit can resonate and elevate the electric stress in the windings beyond the dielectric withstand strength of the windings. A recent IEEE Standard addressed the interaction between breaker switching and transformer response. A Final Thought - The Importance of Padmount Transformer Bushings One of the most common specification errors occurs on padmount transformers. On 34.5 kV rated windings, the highest rated dead front bushing is rated at 150 kV BIL. Thus most specifications also specify 150 kV BIL as the insulation level of the associated winding. Instead, a good practice would be to specify a full 200 kV BIL for the winding, while leaving the bushing at 150 kV BIL. It is much easier to replace a failed bushing than a failed transformer.

Transformer Applications in a Modern Wind Farm

Today's modern utility wind farm consists of a collection of wind turbines distributed in an array that provides the greatest exposure to the local wind flows. Often the array is composed of a series of radial lines of turbines connected in parallel to feed a common "collector" bus. The number of transformers on each radial and the number of radials varies with the site terrain, available area, and individual switching and protection schemes. See Figure 1 for a typical wind farm array layout. Depending upon the design, wind farms may use transformers for six unique functions. Wind Turbine Step-Up Transformers Each turbine is equipped with a transformer to step-up the turbine generator output voltage to the collector system voltage. This transformer also serves as a source for the turbine's auxiliary power requirements when the turbine is off line or generating insufficient power. Proximity to the turbine is critical to limit the length of costly and inefficient high current, low voltage, cables. The typical distribution transformer is often ill-suited to the requirements of a wind farm. We have found that the mismatch between requirements and typical transformer design contributes to the present high rate of step-up transformer failures at wind farms. Grounding Transformers Under normal conditions, the common collector bus will be connected to the substation main transformer. Depending on the system configuration, grounding transformers may be required to provide a system ground as protection circuitry operates. Also, grounding transformers themselves provide a protective function by preventing a faulted phase from staying at ground potential and limiting overvoltage conditions on the un-faulted phases. Grounding transformer sizing is based on the ampere capacity of the radial collector circuit and the time required for de-energization of the turbine and collector circuits when a fault occurs. Substation Main Transformers (Sometimes Known as Collector Transformer) Voltage from the collector system is stepped-up to the sub-transmission or transmission level voltages by the substation main transformer. This intermediate step helps limit the transformation ratio required by the individual wind turbine step up transformers. Some installations might use more than one substation main transformer to limit its size or take advantage of site logistics, depending upon station design philosophy. Transmission Auto-Transformers These transformers provide the flexibility to interconnect to multiple transmission lines with dissimilar voltages. Station Service and Auxiliary Power Transformers Because wind farms are usually located far from developed urban or residential lands, they must be self-sufficient and not require power from external sources. This is particularly important for off-shore installations. Thus, power for such local functions as lighting, heating, switching, tripping, relaying, metering, and communications is provided by the station service transformer connected to the main transmission lines. It is possible to provide some of these functions from a grounding transformer, but this approach is not popular with designers and would not provide continuing power in the case of a fault. Voltage Conditioning Equipment Dynamic-VAR compensation equipment can be used to limit damage to the turbine equipment due to under-voltage conditions and to provide system stability. This equipment requires integral transformers of sizes as high as 8 MVA. The transformers are integral to this equipment, so they are not normally ordered separately or specified by the system designers, as the case is for the other type of transformers in the wind farm environment.

Introduction to Busway

Commercial and industrial distribution systems use several methods to transport electrical energy. These methods may include, heavy conductors run in trays or conduit. Busway, a grounded metal enclosure containing factory-mounted bare or insulated conductors can be an effective method of distributing power. A bus bar is a conductor that serves as a common connection for two or more circuits. Standard bus bars in busway are commonly made of aluminum or copper. A busway is used in numerous applications and can be found in industrial installations as well as high-rise buildings. Busway used in industrial locations can supply power to heavy equipment, lighting, and air conditioning. Busway risers (vertical busway) can be installed economically in a high-rise building where it can be used to distribute lighting and air conditioning loads. Busway provides flexible power distribution solutions for a variety of applications where change and adaptation are important. NEMA Definition National Electrical Manufacturers Association (NEMA) defines busway as a prefabricated electrical distribution system consisting of bus bars in a protective enclosure, including straight lengths, fittings, devices, and accessories. Busway includes bus bars, an insulating and/or support material, and housing. A major advantage of a busway is the ease with which its sections are connected together. Electrical power can be supplied to any area of a building by connecting standard lengths of busway. It is typically faster to install or change than cable and conduit assemblies. The total distribution system frequently consists of a combination of busway, cable and conduit. In many cases busway can be used in lieu of the cable/conduit feeders at a lower cost. Benefits of a Busway If you need to add load to or extend power from an existing distribution system, a Busway systems may be the answer. First introduced in 1932, busway solved the automotive industry's need for a flexible power distribution system to serve its linear layouts. Since that time, this product has grown to serve many other types of loads. Where and How to Apply Busway You can install busway in most applications where you'd normally use cable and conduit. Busway manufacturers produce systems ranging from 100A to 6500A. Low-amperage applications include high-technology firms, such as computer manufacturers and test laboratories. The automotive industry and other heavy assembly industries require high-amperage busway systems. Recognizing the need for flexibility, manufacturers developed elbows and offsets to make directional changes easy. With these fittings, busway offers extensive layout versatility. When new loads develop, it's easy to meet changing conditions by adding tap-off units and/or new sections. However, busway is not the best solution for every application. For example, if the situation requires low current to a specific source, you're better suited for cable and conduit, which is best for underground applications. Also, Sec. 364-4(b) of the National Electrical Code (NEC) says you cannot install busway where it's subject to severe physical damage or corrosive vapors. Benefits to End Users Busway provides an effective means of distributing power in a building. Since it requires easy maintenance procedures and is flexible, it's relatively simple for accommodating changing load situations. Maintenance primarily consists of annual inspection of joint fittings using an infrared heat gun, and then using a torque wrench to tighten appropriate connecting bolts. If required, it is possible to cut power to only a portion of a busway run so one can perform any required maintenance without risk of injury or equipment damage.

Industrial Control Transformers

Industrial Control Transformers are intended for industrial applications where higher single-phase voltages need to be converted down to usable AC line voltages. Even before selecting an Industrial Control Transformer, various specifications must be kept in mind like load, minimum voltage required for operation, inrush load power factor etc. Industrial Control Transformers are designed with very low temperature rise, exceptional voltage regulation and great overload capacity of high momentary in-rush current demand by the contactors, relays and solenoids. The voltage drop under high transitory in-rush current is also very low, which guarantees satisfactory operation of contactors, relays and solenoids. Features of an Industrial Control Transformer An Industrial Control Transformer is usually, Encapsulated in epoxy which seals the transformer coils against moisture, dust, dirt and industrial contaminants for maximum protection in hostile and industrial environments Fuse clips for most models. Factory mounted for integral fusing on the secondary side to save panel space, save wiring time and save the cost of buying an add-on fuse block or kit Integrally molded barriers between terminals and transformer protects against electrical creepage. Up to 30% greater terminal contact area permits low-loss connections. Extra-deep barriers reduce the chance of shorts from frayed leads or careless wiring Terminals molded into the transformer are difficult to break during wiring. A full quarter-inch of thread on the 10-32 terminal screws prevents stripping and pull out Two jumper links are standard with all transformers which can be jumped Operation of an Industrial Control Transformer Industrial control circuits and motor control loads typically require more current when they are initially energized than under normal operating conditions. This period of high current demand, referred to as an inrush, may be as great as ten times the current required under steady state or normal operating conditions, and can last up to 40 milliseconds. A transformer in a circuit subject to inrush will typically attempt to provide the load with the required current during the inrush period. However, it will be at the expense of the secondary voltage stability by allowing the voltage of the load to decrease as the current increases. This period of secondary voltage instability, resulting from increased current, can be of such magnitude that the transformer is unable to supply sufficient voltage to energize the load. The transformer must therefore be designed and constructed to accommodate the high inrush current, while maintaining secondary voltage stability. According to NEMA standards, the secondary voltage would typically be 85% of the rated voltage. Selecting an Industrial Control Transformer Should your organization be looking to invest in a industrial control circuit transformer, the following is what you need to understand: Inrush VA is the product load voltage (V) multiplied by the current (A) that is required during circuit start-up. It is calculated by adding the inrush VA requirements of all devices, which will be energized together. Seated VA is the product of load voltage (V) multiplied by the current (A) that is required to operate the circuit after initial start-up or under normal operating conditions. It is calculated by adding the sealed VA requirements of al electrical components of the circuit that will be energized at any given time. Primary Voltage is the voltage available from the electrical distribution system and its operational frequency, which is connected to the transformer supply voltage terminal. Secondary Voltage is the voltage required for load operation which is connected to the transformer load voltage terminals. Primary Fuse Kit this kit includes a 2-pole class CC fuse block, instructions and all associated mounting and wiring hardware. Industrial control transformers from Pacific Crest Transformers Pacific Crest Transformers builds industrial transformers specifically designed to meet client needs to provide feeder voltages to the single phase control transformers described in this article. We also offer Custom Design Transformers to meet the most demanding industrial situations without compromising on quality and performance levels. Custom designed transformers are manufactured keeping in mind specifications given by the clients and industry standards. Our transformers are built to handle the roughest industrial situations.

Acceptance Testing and Maintenance of Power Transformer

An energy transformer is a rather critical piece of equipment and this makes its installation a monstrous task that needs to be well backed by a good testing and inspection program. Power transformer testing and inspection should ideally start with the installation of the transformer and continue throughout its life. The initial acceptance inspection, testing and start-up procedures are extremely critical. The inspections, both internal and external, will reveal any missing parts or items that were damaged in transit. It will also help you verify that the transformer is constructed exactly as specified. The acceptance tests will also reveal manufacturing defects if any and establish baseline data for future testing. The start-up procedures should ensure that the transformer is properly connected, and that no latent deficiencies exist before the transformer is energized. Ensuring that the transformer starts off as it should is the best way to guarantee dependable operation throughout its service life. Manufacturers recommend a wide range of acceptance and start-up procedures and it is best to follow them strictly. Power transformer maintenance A power transformer is a fairly reliable piece of electrical distribution equipment. With no moving parts, transformers requires minimal maintenance, and are capable of withstanding overloads, surges, faults, and in some cases even superficial physical damage. While transformers can withstand a lot of electrical fluctuations, they do deteriorate with age, and thus need constant monitoring to detect and correct problems before they escalate into expensive repairs. This is where a good inspection, testing and maintenance program comes in. Heat and moisture related contamination are the two greatest enemies of a transformer's operation. Heat breaks down transformer insulation and accelerates chemical reactions that take place when the oil is contaminated. One of the ways to address the heat problem in a transformer is to ensure the transformer is properly cooled, through regular cleaning of the cooling surface, maximizing ventilation, and monitoring load to ensure the transformer is not producing excess heat. Contamination is detrimental to the transformer, both inside and out. Dirt and grease deposits severely limit the cooling abilities of radiators and tank surfaces. The oil in the transformer should be kept as pure as possible. Dirt and moisture will start chemical reactions in the oil that lower both its electrical strength and its cooling capacity. Contamination should be the primary concern any time the transformer is opened. Most transformer oil is contaminated to some degree before it leaves the refinery. It is important to determine how contaminated the oil is and how fast it is degenerating. Determining the degree of contamination is accomplished by sampling and analyzing the oil on a regular basis. Although maintenance and work practices are designed to extend the transformer's life, it is inevitable that the transformer will eventually deteriorate to the point that it fails or must be replaced. Transformer testing allows this aging process to be quantified and tracked, to help predict replacement intervals and avoid sudden failure.

Going Beyond Wind and Solar Farms

Recent years have seen tremendous focus on renewable energy in the US. Emphasis has been on wind and solar energy and a lot of attention seems to have been concentrated on the desert areas of Southern California. With millions of acres of sandy area, the Mojave and Colorado deserts offer an ideal opportunity for huge wind and solar farms. Interestingly, the US government too has put its final stamp on a number of projects, many of them are being fast tracked, and California is now poised to become the solar energy capital of the world. But while a lot of attention is being laid on generating energy from renewable sources and much revenue is being funnelled towards it, is putting up solar and wind farms all it takes to reduce our dependence on fossil fuel, many would think not. Is the energy infrastructure ready for renewable energy? Renewable energy generation seems to be only part of the issue, also of importance is the distribution and transmission infrastructure like transformers. The US has one of the largest energy production, transmission and distribution machineries in the world. Unfortunately, much of it is aging. The aging energy transmission, distribution network and aging transformers are causing reasonable energy waste; the energy distribution system also needs to be upgraded to take on the additional task of dealing with variance in energy from fossil fuel to renewable. Undoubtedly, renewable energy from solar and wind have the potential to power millions of homes across the United States. Though initially capital intensive, renewable energy has the propensity to pay for itself in a matter of years, reduce the country's carbon footprint and dependence on foreign oil, however, before we begin tapping into the benefits of renewable energy we need to have infrastructure in place that stores, distributes and transmits energy efficiently. Problems associated with renewable energy One of the biggest drawbacks of renewable energy is its fluctuating supply. This problem can only be resolved by putting up storage units for renewable energy and storing it when it is being generated plentifully and used even when supply is low. Huge storage batteries seem to be the ideal solution. The smart gird is yet another aspect of the infrastructure that needs to be responsive and 'smart' enough to address issues caused by fluctuating energy levels, track energy distribution and pre-empt energy disruption. The biggest issue however presents itself in the form of energy transformers. Energy transformers play a vital role at every step of the way, from collecting energy at solar and wind farms, to stepping it up for transmission and then stepping energy down at multiple levels for consumption. Thousands of energy transformers in the United States are rapidly aging, they need to be replaced by energy efficient distribution transformers that are hardy and able to transmit energy generated by both fossil fuel and renewable sources. Pacific Crest Transformers is ready for renewable energy Pacific Crest Transformers is doing pioneering work in manufacturing a range of energy efficient distribution transformers for the renewable energy sector, especially wind farms. We have designed and custom-built Wind Turbine Step-Up Transformer to increase efficiencies in the renewable energy market. Our transformers are built with a cruciform core, robust winding, clamping structures, seals and gaskets, and have in-built protective measures to prevent hot spots and partial discharges, so that your transformer has a long life. Much like rectifier transformers, Wind Turbine Step-Up Transformers are designed for harmonics, additional loading, and have electrostatic shields to prevent transfer of harmonic frequencies between the primary and secondary windings. So while the emphasis is currently on producing renewable energy, it's time to seriously consider the capabilities of our transformers to adapt to our changing energy needs.

Green Technology is the new 'Efficient'

Growing demand for energy According to the North American Electric Reliability Corporation (NERC), the demand for electricity in the US continues to grow, even while concerns over long term reliability of supply persist. The Energy Information Administration (EIA) predicts the country's electricity demand will grow at the rate of 1.8% to 1.9% percent per year till 2025. To keep pace with this increasing demand the US must add approximately 300,000 MWe of new capacity over the next 16 years. Exploring energy alternatives As our dependence on energy continues to increase, the search for efficient alternatives remains prominent. There are broadly two pressing needs that propel this search. The first, growing scarcity and cost of fossil fuel; the second, strong environmental concern due to increasing amount of green house gases being released into the atmosphere. Thus far green, energy-efficient technology seems to be the best answer to our energy needs. It reduces our dependence on expensive imported fossil fuel, reduces our carbon footprint and is gradually becoming cost effective. Energy-efficient green technology is making its presence felt in a number of ways - most prominent being the growing use of renewable energy like solar, wind, hydro and geothermal. A second method is using smart grid and other energy efficient infrastructure like energy efficient transformers. Could Wind energy be part of the answer? Technological progress has enabled a ten-fold increase in the size of wind turbines, from 50 kW units to 5 MW, in 25 years and a cost reduction of more than 50% over the last 15 years. The U.S. Department of Energy's Wind and Water Power Program is now working with wind industry partners to develop clean, domestic, innovative wind energy technologies and aims to reach a target of meeting 20% of the nations energy needs from wind energy by 2030. With wind energy available in abundance, it is being widely seen as key suppliers to bridge the energy demand supply gap. Pacific Crest Transformers Edge We at Pacific Crest Transformers have had a long term presence in the area of green, energy-efficient technology. Over the years we paved the way to energy-efficient transformers by developing and testing them first within our premises and then delivering them as quality solutions to clients. We introduced fundamental changes in the production of transformers and began manufacturing custom, energy efficient and environmentally friendly transformers even before legislations made it mandatory for companies to comply.

Transformer Oil Maintenance

Energy transformers are critical components of the energy distribution grid and it is therefore important to have a monitoring and maintenance plan in place to preempt their failure. One of the critical components of an energy transformer is the transformer oil. A transformer operates in a moisture free environment and even the slightest moisture can seriously reduce its life. Most companies have an oil maintenance schedule to monitor the condition of oil and detect a problem before it causes extensive damage. Oil testing during maintenance also helps detect problems like contact arcing, aging insulating paper and other latent faults. Steps for Collecting Oil Sample for Transformer Oil Testing: Oil testing is a critical process it can be done before the transformer start-up, during a routine transformer inspection or in any circumstances indicating possibility of damage to the transformer, particularly when a protective device is triggered. To collect an oil sample a sampling valve located near the bottom of the tank is used. Transformer oil is a hygroscopic substance and must be protected from contact with moisture. It is therefore important to place the collected oil sample in a clean dry container. Oil Treatment Guidelines Following are the oil treatment guidelines which can prolong the life of transformer and save a company thousands of dollars: Purify when the acid level is still low, i.e. <0.1 mg Regenerate preferably from 0.1 mg KOH/g oil to avoid precipitation of sludge De-sludge when the acid level is >0.20 mg KOH/g oil Dry-out when the solid insulation is wet >3.5 % MDW Purification, a method of transformer oil maintenance Purification is the process by which moisture and gasses are removed from the insulating oil. This process readily dries up the oil but not the insulation system, this is because the drying depends on the rate of diffusion of water through the paper into the oil, which is slow. Frequent processing is necessary to attain the degree of dryness desired in the cellulose insulation. Even though the purification method is not the best, it is an effective moisture management tool. It is used widely in the industry to effectively reduce the moisture content and elevate the dielectric strength of the oil in wet core situations.

NFPA Compliance and Electrical Transformers

Even though energy transformers typically deal with hazardous levels of electricity, they are often located in or near fairly public places. Their safety is thus a matter of much concern. For this reason, requirements for electrical transformers and employees working with them are included in NFPA 70 and 70E. All electrical wiring and equipment has to be in accordance with NFPA 70. With electricity being hazardous, employees working with transformers are also subject to protection in accordance with 70E, unless it is an existing installation, which may be permitted to continue in service, subject to approval by the authority having jurisdiction over it. Below are some of the key provisions relative to transformers mentioned in NFPA 70: Individual dry-type transformers of more than 112 kVA rating should be installed in a transformer room of fire-resistant construction having a minimum fire rating of 1 hour. Transformers not over 112 kVA have no specific installation requirements for the room in which they are located. Dry-type transformers rated over 35,000 volts should be installed in a vault with minimum fire resistance of 3 hours. Each doorway leading into a vault from the building interior should have a tight fitting door that has a minimum fire rating of 3 hours. Exception: Where transformers are protected with automatic sprinkler, water spray, carbon dioxide, or halon, construction of 1-hour rating shall be permitted. About NFPA 70E The NFPA 70E standard addresses the electrical safety requirements for all employees who install, maintain and repair electrical systems. It recognizes the hazards associated with the use of electrical energy and includes guidelines to take precautions against injury or death. Compliance to NFPA 70E requires that all personnel working on electrical equipment operating at >50V should wear arc-flash protective garments to prevent injury. Arc-flash is an electric current that passes through the air when the insulation between electrified conductors can no longer withstand an applied voltage. A flash can last less than a second and its results can be severe and even lead to fatalities. NFPA 70E Compliance Checklist Implementation of NFPA 70E regulations is a major challenge. The arc flash analysis requires training and tools to implement the program. Below is a checklist to establish NEPA 70E Compliance Short-Term Action Electricians, maintenance mechanics and facilities repair workers are not to work on hot/live equipment wearing all-cotton clothing Electricians, maintenance mechanics and facilities repair workers should work as much as possible on de-energized equipment. Employees are to use interim hazard warning labels on electrical equipment. Long-Term Action Electrical workers are to be trained in Arc-flash Hazard Awareness. Existing Logout/Tagout (LOTO) procedures are to be periodically reviewed to make certain they include all control panels. The LOTO training of previous employees to be assessed to determine if they need to be retrained. Periodic tool audits to be conducted to ensure employees have the required tools for their safety and replacement of missing tools. Reviewing those employees have clothing appropriate for electrical work. Arc-flash hazard analysis to be conducted to determine flash protection boundary on switchboards, panel boards, industrial control panels, motor control centers, other similar equipment. So if you are planning to buy a transformer, you might want to ensure your transformer is NFPA 70 and 70E compliant, and pay some special attention to transformer security and safety of employees working with them. Pacific Crest Transformers, with its years of experience on safety, advises those buying transformers from them on how to comply by the required legislation, so that risk of any kind is minimized.

High Voltage vs. Low Voltage Transformers

If your company is planning to invest in a power transformer, it is best to get as well acquainted with these devices as possible, before you ask for quotes and go about buying one. A transformer is a complex and vital component of power transmission and once installed, its life could span anywhere from two to three decades. It is therefore important to make a wise and knowledge-based choice. There are a few basic things about transformers that you must know. The first is the voltage aspect. There are broadly three voltage ratings in which transformers are available, high voltage, medium voltage, and low voltage. Below is a brief that should help you understand each of them better. High voltage transformers The high voltage transformer deals with voltages that cannot be used directly by the consumer, but are used in power transmission applications. High voltage transformers usually handle electrical energy in the range of 230,000 to 35,000 volts. Due to the particular demands of transmitting these voltages across long distances, a high voltage transformer has considerably different core geometry, winding methods, and insulation methods than low voltage transformers. High voltage transformers that have the capacity to increase the primary voltage to transmission-level high voltage are called step-up transformers. Conversely, high voltage transformers can also be used to step-down voltages, depending on where they are in the transmission chain. Some of the applications of high voltage transformers are in electrical isolation, instrumentation and power distribution and control. This type of transformer can also be easily configured from single phase to three phase. Medium voltage transformers Transformers in this range are typically deployed in the local distribution sector of the power delivery system. They range from 35,000 volts to 2,400 volts and are used to deliver power from local distribution circuits to end users. Where residential customers are the end user, the output voltage can be as low as 120 volts, or for industrial customers, it can be 5,000 volts. This transformer can be viewed as a link from the end user to the utility provider. These transformers are most often seen mounted on utility poles or as green boxes with tamperproof enclosures for connections located in shopping malls, residential subdivisions, schools and mobile home parks, in newer residential developments they can even be seen along sitting curb-side in front of the users home. These are usually liquid filled and are by far the most numerous of the three sizes. Low voltage transformers A low voltage transformer, also sometimes called a magnetic low voltage transformer, is typically used at the consumer end of the energy grid. A low voltage transformer is a distribution transformer with both the primary and secondary windings designed to operate at system voltages in the low voltage classes. Typically, electronic low voltage transformers convert 120 volts into 12 volts or 24 volts. A DC low voltage transformer uses a rectifier to convert its output to direct current (DC) and to lessen radio frequency interference (RFI). Low voltage transformers offer a variety of mounting configurations and are often small in size. So unless your company is a huge steel plant, has a huge furnace, or runs machinery for the mining or petrochemical industry, in all probability your company will have to invest in a medium or low voltage transformer. The exact rating (expressed in terms of kVA), of course, will depend on your energy requirement. Whatever your eventual requirement, it is important that you consider vendors that can provide customized, environmentally friendly units that conform strictly to DOE standards.

Transformers and Safety Requirements

The century-old power grid is the US is the largest interconnected machine on Earth. It consists of more than 9,200 electricity generating units, with more than 1,000,000 megawatts of generating capacity connected to more than 300,000 miles of transmission lines. Holding this mammoth infrastructure together are all types of station, substation and pad mounted distribution transformers. With transformers being the major hub of collection and distribution of high voltage current, it is but natural that safety is a major concern, especially when they are located in public places and residential areas. Thankfully, there are also numerous techniques and both on- and off-line monitoring systems that can be used to increase operational efficiency, security and minimize unscheduled downtime. This might be common knowledge but it's good to remind ourselves that when dealing with electricity it is important to remember that it travels at the speed of light which is about 186,000 miles per second. It not only quickly, but also very easily, passes through things like the ground, metals, and anything with moisture in it. Electricity can also jump short distances through the air. Transformers receive and distribute very high voltage electricity, and leakages can thus be catastrophic. Things to consider when dealing with safety related to transformers: Before installation of a transformer, inspect where it will be housed carefully and look for potential safety issues, including dampness, water and moisture, unless the transformer is designed for that type of environment. When access panels are removed for cleaning, all insulation surfaces should be inspected for signs of discoloration, heat damage, or tree-like patterns etched into the surface that are characteristic of corona damage. The core laminations should be inspected for signs of arcing or over-heating. Identify the type of electrical hazard and what agency maintains it. Determine if extinguishment is required. If so, use dry chemical or carbon dioxide for extinguishment of electrical equipment. Beware of gradient grounding. Assume all equipment is energized until the proper agency deems safe. Learn to identify potential hazards around your transformer: these include frayed wires, dampness, and more. Visually inspect your transformer on a routine basis and replace frayed cords or wiring to avoid leakage of electricity. If the transformer sparks, shocks, smokes or doesn't seem to be operating normally, turn if off immediately. Avoid overloading the transformer by exceeding the rated load. Overloading can lead to overheating and extensive damage to the transformer. Put in place a regular maintenance plan for the transformer. The issue of transformer safety gains a lot more relevance considering the fact that the US has a largely aging power infrastructure. Aging substation transformers installed in the 1960s and 1970s are rapidly approaching the end of their 'life'. These transformers didn't cause a blip on the radar during the last two decades, but with every year of the 21st century, their failure rates have become increasingly difficult to predict. This means that resource allocation and repair/replacement decisions are also becoming more and more exigent to maintain transformer safety.

Coping with Increasing Energy Demands in the US

According to Red Herring Inc., energy demands in the US are likely to surge by 32% in 2015. But even after being one of the highest energy consuming economies in the world, the US has come full circle. It is now one of the more aggressive nations in promoting alternative energy technologies. Growing environmental concerns like Global Warming and the need for energy self-sufficiency has introduced in the minds of many US citizens a need to be more energy-efficient. The last few years have seen the launch of several energy-efficient electronic appliances and automobiles. The US now plans to put in place infrastructure for harnessing and distributing alternate energy like solar, wind, hydro and thermal. A lot of investment - both government and private - is also being made towards this end, bringing down the cost of alternate energy. In the 1980s the average price of energy captured with photovoltaics was 95 cents per kilowatt-hour. With technological improvements and tax benefits, solar-electric modules have now become more cost-effective. In 2008, the price had dropped to around 20 cents per kilowatt-hour, according to the American Solar Energy Society. The US also currently has about 4.2 billion solar rooftops and as the popularity of solar energy increases, one can only expect the technology to become much more cost-effective. The presence of wind energy in the US is also growing. According to the American Solar Energy Society, Wind power now competes with conventional energy at a price less than 4 cents per kilowatt-hour. In 2008 the US had roughly 300 million wind turbines . So industry and consumers can expect cost reduction on this front too. The US is not alone in adopting many of these measures, as they are no longer an option; they are an imperative for a sustainable future. To be sure, there are many more problems to solve - for example, if 25% of the population switched to electric cars tomorrow, the demands on the power grid would be impossible to satisfy and much thought and effort has to go into building the right infrastructure in a phased manner. Transformers, of course, will continue to play a crucial role in any power infrastructure. Transformers currently contribute to a sizable amount of the energy lost in transmission, prompting the US Department of Energy (DOE) to come up with regulations to ensure that old transformers are replaced with more energy-efficient ones. This has hiked the cost of medium-voltage, dry-type transformers almost 13%, but will decrease electrical losses by as much as 26%. It is in this area of building energy-efficient transformers that PCT plays a prominent role. PCT has years of experience in manufacturing customized energy-efficient transformers - in some aspects PCT has also been ahead of legislation. Currently PCT is also gearing up to meet demands of the wind energy sector with its specially designed, robust grounding transformers. While the initial investment in energy-efficient transformers may seem high, so far it seems that utilities and industries are more than willing to invest in them, as the transformers pay for themselves very quickly over time.

Aging Power Infrastructure in the US

The US electric grid is a mammoth, complex network of independently owned and operated power plants and transmission lines. Most of the currently available infrastructure was put in place across the 1950s and 60s. Its sheer age is now earning commentary like this, on NPR: "The U.S. power grid is often equated to a highway system, one that has been seriously neglected and is now being pushed to its limits with the demands of our growing and changing energy needs. As we see the rise in demand for renewable energy sources to combat the environmental ramifications of fossil fuels, the grid will continue to be proven antiquated and in need of reinvention." The Department of Energy estimates that demand for electricity has increased by around 25 % since 1990 while construction of transmission facilities dropped 30%. According to Media Company Red Herring Inc., energy demand in the US is likely to surge 32% by 2015. The grid failure of 2003 that affected the lives of over 50 million people is an oft-quoted example to underline the necessity of modernizing the US power grid. This is not just to deal with growing demand, but also to accommodate the new focus on renewable energy sources like wind, solar and hydro power: which are not easily inter-connectable to the existing grid without significant refurbishing. The goal, of course, is to address long term energy security. Opting for renewable energy and putting in place infrastructure like 'smart grids', however, calls for a sizable investment. A key target to reduce energy lost in the distribution process is the emergence of higher efficiency requirements for power and distribution transformers. Currently, transformers are responsible for a sizable amount of the energy lost and it is here that the DOE is introducing rules to increase efficiency. According to the rules published by the DOE, the cost of liquid-immersed distribution transformers increases by up to 12%, but should decrease electrical losses by as much as 23%. It could also raise the cost of medium-voltage, dry-type transformers by up to 13%, but should decrease electrical losses by as much as 26%. It is in the area of energy-efficient transformers, and transformers in the alternate energy sector like wind energy that Pacific Crest is making its presence most felt. With over 90 years of continuous experience, PCT has also been a consistent innovator in building custom energy-efficient transformers. This has allowed PCT to keep pace with the new energy-efficient power grid that is replacing the aging infrastructure. Although much of the energy efficient technology is a little more expensive, private and government-owned utilities have begun to invest in it for the reliability it ensures. Additionally, the initial investment more than pays for itself in the long run, due to the decreased energy lost in the transmission and distribution system.