Skip to main content

What are Static Synchronous Compensators (STATCOMs)?

Used to support power factor and/or voltage regulation and for utility-scale renewables interconnections.

  • How do you choose the correct, most cost-effective Clean Power Solution?

      Not everyone has the same power problem. Finding the most cost-effective solution requires some analysis of your equipment, the power system and the available solutions in the market. The table below lists causes and effects of many common power problems. You or your electrician can determine the most likely cause of power problems based on knowledge of your location, the kinds of equipment you operate in that location, and the kind of power distribution system in your building.

      The following table lists the types of Clean Power products available from HPS to solve your power problems.

      Table for clean power

       

      HPS offers the following products for clean power solutions:

       

  • Iron core filter reactor – definition
  • Air core filter reactor – definition
  • What is EMF (Electric and Magnetic Fields)?
  • What Effects Does EMF (Electric and Magnetic Fields) Have on Equipment?
  • What are Static VAR Compensators (SVCs)?
  • What are Static Synchronous Compensators (STATCOMs)?
  • What is Series Compensation?
  • Why is Clean Power so critical?

      Your computer is a delicate electronic instrument. When you use the keyboard, you’re sending a series of tiny electronic impulses through the computers circuits. The computer ‘reads’ these electronic impulses and makes calculations or performs tasks according to your programmed instructions. If the electrical power feeding your computer is smooth and clean, your computer will behave normally. However, if the power fed into your computer is “dirty”, you could be in for many unpleasant surprises.

      Practically all electronic devices are sensitive to fluctuations in voltage, therefore clean power is vital in order to ensure uninterrupted performance of modern-day electronic equipment.

  • What is IEEE 519-2014

      IEEE is the Institute of Electrical and Electronics Engineers. IEEE 519-2014 is a document that establishes levels of voltage and current harmonic distortion acceptable to the distribution system based on the input transformer characteristic and the loads on a customer’s facility. Many electrical consultants are including compliance with IEEE 519-2014 in their design specifications to help reduce harmonic problems and avoid penalties that can be imposed by electrical utilities. More information about the levels of harmonics can be found on the IEEE website.

      • The IEEE 519-2014 also outlines the Point of common coupling (PCC) as the point where the utility meets the facility
      • The current and voltage harmonic limits set by IEEE and followed by many specifiers are clearly outlined in the following IEEE tables shown below:

      Voltage Distortion Limits & Maximum Harmonic Current Distortion

  • Does the VFD have to be equipped with a DC link choke to work with Active Harmonic Filter
  • What is an active harmonic filter?

      Due to the increasing usage of non-linear loads such as VFDs, harmonics are being introduced into the power grid which is contributing to poor power quality and leads to overheating of equipment and nuisance faults. Active Harmonic Filters are parallel devices that are used to mitigate harmonics to the levels defined by IEEE-519.

      HPS TruWave AHF utilizes high frequency current sensors to continuously monitor the load and harmonic currents. By utilizing highly sophisticated software and a powerful DSP microcomputer, the system is able to instantaneously inject a corrective current from its IGBT based inverter to dramatically reduce harmonic distortion. The corrective current is equal to but 180 degrees out of phase with the existing harmonic currents to cancel their effect.

      Active filters work on the same principle s as noise cancelling head phones except they cancel harmonic currents and reduce distortion.

  • What are the benefits of an active filter over a passive filter

      Here are some of the advantages that Active Harmonic Filters can provide over the Passive Filters.

      • Active Harmonic Filters provide far superior flexibility and performance over passive filters.
      • Not all Passive filters can achieve the 8% or 5%THD IEEE-519 specification even at full load. The HPS TruWave AHF will achieve less than 5% THD even until 10% loaded. Passive filters typically provide less overall mitigation as the load decreases.
      • AHF will not cause a leading power factor at no load while passive filters do
      • AHF can be installed anywhere in the lineup, while the passive filters must be installed at each VFD
      • Active filters are cost and space effective with the use of multiple VFD loads compared to passive filters

  • Do I need to use a line reactor with VFDs to work with an Active Harmonic Filter

      All non-linear loads must have an input line reactor (minimum 3%) or a DC link choke to achieve the desired system performance. While an AHF can correct harmonics without line reactors, issues can occur if there is not sufficient impedance between an AHF and a load.

      Using line reactors is also cost effective since reactors mitigate some of the harmonics and a smaller AHF can be deployed.

  • Can I use Active Harmonic Filter for single phase loads

      An active harmonic filter cannot be used to correct harmonics from single-phase harmonic sources. AHF’s correct the harmonics from three-phase sources and therefore are also only designed to run on three-phase systems.

      Isolation transformers and line reactors can mitigate some of these harmonics from single-phase sources. Three-phase system with large loads of single-phase harmonic sources can also use Harmonic Mitigating Transformers (HMT).

  • Can I use PFCC with Active Harmonic Filters

      Power Factor Correction Capacitors can be used on systems with AHF’s. AHF’s harmonic mitigation may even be required to protect PFCC from excessive heating and failure caused by harmonics. PFCC cannot be installed on the load side of AHF current sensors. PFCC should be installed between the AHF and the utility point of common coupling (PCC).

  • Can and Active Harmonic Filter improve power factor
  • How many CT do I need to use for the Active Filter

      CT’s are used with the HPS TruWave AHF to continuously monitor the load and harmonic currents. Typically, if the system only has three-phase loads downstream to the AHF, two CT’s can be used; the TruWave software will calculate the third phase current. If the system has any single-phase loads, a third CT is required.

      Here are some the installation considerations for the current transformers (CT’s) with the AHF:

      • Must be located upstream of VFD loads requiring correction
      • Two CT’s are required for the correction of three-phase loads
      • A third CT is only required if there are also single-phase (line to neutral) loads
      • The CT’s are sized based on the current rating of the bus

  • What are the main functions performed by an Active Harmonic Filter
  • What does AHF stand for
  • What communication options come with the HPS TruWave Active Harmonic Filter
  • Which applications are best addressed by an Active Harmonic Filter

      AHF’s are used where a significant portion of the load consists of VFD’s or other three-phase non-linear sources such as large three-phase DC power supplies, electric vehicle chargers or UPS’s. VFDs are defined as non-linear loads which generates an enormous amount of harmonics in a system. Harmonics cause a host of electrical problems. AHF’s are great candidates to mitigate harmonics from a system where multiple VFD loads that represent a significant portion of the total load.

      Active filters are designed to reduce harmonics from three-phase sources. For single-phase harmonic sources, solutions such as harmonic mitigating transformers should be considered.

  • What information is needed to size an Active Harmonic Filter

      The following information is all required in order to correctly size an active harmonic filter:

      • One-line diagram of the system. Location and size of VFD’s and Power Factor Correction Capacitors is very useful.
      • Detailed equipment lists can also be used, especially in conjunction with one-line diagrams.
      • VFD information: Horse Power or Current size.
      • Are line reactors being used with each VFD? If so what is the impedance?
      • Will the active filters operate on generator?
      • Are there any large soft start loads located downstream of the AHF?
      • Local Environmental Conditions

  • What information does the TruWave Active Harmonic Filter display give
  • What Output Problems Can Occur with Variable Frequency Drives (VFD or VSD) and How Can You Mitigate These Issues?

      A voltage-sourced Variable Frequency Drive (VFD) uses Insulated-Gate Bipolar Transistors (IGBTs) to rapidly switch voltage on and off to form a Pulse Width Modulated (PWM) voltage source for the motor. The PWM simulates a sine wave voltage source to the motor and it operates as if it was being powered by a sine wave.  The PWM wave allows the VFD to change the fundamental frequency of the PWM waveform and simulate sine waves.  Since the speed of a motor is directly related to the fundamental frequency of the sine wave, a VFD can control speeds from a fraction of a hertz to hundreds of hertz.

      Output reactors, dV/dT filters or drive isolation transformers can be used to help mitigate some issues caused by the PWM output.  PWM outputs cause rapid switching transitions which can cause over-voltages due to parasitic capacitance and inductance in the motor’s leads. The parasitic currents and voltages can be determined by the equation of V = L × (Δi/Δt).  VFD’s switching frequencies (the amount of pulses used to simulate the sine wave) generally range from 1,000-20,000 pulses per second.  IGBT’s produce an almost perfect square wave which produces a very high Δv/Δt.   High Δv/Δt can cause higher surge currents in the leads. This then causes high voltage pulses across the parasitic inductances.  Therefore the faster the pulses switch, the greater the impact of cable capacitance and inductance. These voltage pulses stress the motor’s windings causing higher audible noise, heat and possibly premature failure of the insulation. There is also capacitance in the motor’s bearings.  The combination of lubrication and air gaps prevent direct and continuous contact of the bearings to the metal traces that contain them.  Parasitic currents [I = C × (Δv/Δt)] causes current to flow through the bearings.  The amount of current will increase as the VFD output switching speed increases. These currents can cause micro pits to form in the bearings and eventually will lead to premature bearing failure.

  • What is ANSI NETA ATS-2017?
  • common transformer installation issues

      Improper Secondary Ground
      If the secondary of the transformer is not grounded properly, the output voltage will look ok between the phases but it will float and not be referenced to earth ground.

      Back-Feeding Delta Primary/Wye Secondary Transformers
      While a base wye secondary transformer can be field modified to backfed, the field modifications may violate U.L., NEC or local code and the transformer’s warranty. Don’t back-feed delta/wye transformers.

      Back-Feeding Transformers above 1 kVA
      Back feeding larger transformers can result in high inrush currents upon transformer energization and nuisance tripping of circuit breakers and fuses. Due to a number of factors which affect inrush, this issue is difficult to predict and costly to fix. The best way to handle this is to purchase transformers wound as step-up. If this isn’t feasible, transformers should be sized to the maximum amperage protection allowed by code, the larger the transformer, the more potential for this to occur.

      Power Wires Routed over the core and coils
      The are being ventilated through the core and coils can be very hot, in excess of 100oC. This can cause wire insulation failure.

      Power Wires terminated in the bottom of the transformer compartment
      Conduit should not be terminated in the bottom of the transformer with a grated floor. The grated floor is needed to provide airflow to cool the transformer but the grates provide a poor surface to mount a coupling and may also violate NEC code.

      Missing Vibration Pads or Vibration Isolators
      All transformers vibrate at 120 hz because of the electromagnetic field in the core. These vibrations and audible noise can transfer through the floor, vibration pads and isolators help to minimize this issue in commercial applications.

      Missing Drip Shields
      While all outdoor applications need a minimum of a NEMA 3R enclosure, even indoor applications near sprinklers would require a minimum NEMA 2S enclosure and therefore drip shields.

      Transformer Harmonic Heating
      Due to the prevalence of non-linear loads and the harmonics they produce, transformers can overheat if not specified properly. As a rule of thumb, if a load contains 25-50% non-linear sources, use K=4, if a load exceeds 50% non-linear sources use K=13.

      Transformer Ambient Heating
      Transformers need to be placed in locations that allow proper ventilation to remove the heat they produce during normal operation.

      More troubleshooting

  • What are some of the solutions to Dirty Power?

      The solutions are as wide ranging as the problems. So are the prices. This Table summarizes some solutions and their price ranges.

      Table for dirty power

      Unfiltered Surge Fuses are very inexpensive, and may provide damage protection from lightning strikes or other surges, but they do not filter out adverse noise.

      Filtered Surge Suppressors are inexpensive solutions to noise suppression and surge protection. The better units inhibit surges above 5000 volts, 200 amps. They should also provide noise filtration of 10dB or more to cover average power disturbances.

      Computer Regulators or Line Voltage Conditioners protect equipment from both noise and voltage fluctuations. They are an inexpensive solution, available in both portable and hardwired models. They provide ideal protection in high noise areas where voltage fluctuations exceed the regulating range of the computers power supply.

      Super Isolation Transformers provide inexpensive protection against frequency variation or noise related disturbances. This is adequate where voltage fluctuations are not a serious problem. Most high-end computers have built-in voltage regulation, but still require protection from line noise.

      U.P.S. Systems are in effect self-contained power centers. They provide backup power for a period of time when utility power is interrupted. Most U.P.S. systems also provide noise filtration and surge suppression.

  • How do you properly size a distribution transformer?

      Distribution transformers need to take several items into consideration when sizing including:

      • Maximum Load
      • Potential future load growth (typical is 25%)
      • Load Inrush and voltage regulation
      • Harmonics and Power Factor
      • Ambient Temperature
      • Additional Service Factor

      For reference, NEC Article 210, Branch Circuits, and NEC Article 230, Services is used to select panelboards and the size of branch circuits. Typically a transformer must be sized to support the load requirements of the switchgear, panelboards and branch circuits. For drive isolation transformers, it is suggested to take sizing charts provided by manufacturers into consideration due to derating for harmonics. In addition to sizing a transformer, the general types including general purpose, K-Rated, Harmonic Mitigating and Drive Isolation also need to be chosen.

      Distribution transformers are often sized from loads based on NEC Article 220. NEC Article 220.87 does allow transformers to be sized based on peak-load data over a 1-year period. NEC also allows loads to be sized using metered data over 30 days if the additional maximum anticipated heating and/or cooling load is also factored in. This often allows a transformer to be sized lower than the base calculations from NEC Article 220. Peak efficiency for 600V class distribution transformers is typically at 35%. Peak efficiency for medium voltage transformers is typically at 50% load.

      Additional capacity for future loads can be obtained by A) specifying a lower temperature rise (15%-30% for dry type) or B) utilizing fans (25%-50% for dry type).

  • Line reactor – definition
  • What is electrical noise?

      Noise is a very broad term that can be applied to a number of AC power line disturbances. Lightening surges or any other sudden changes in load, such as switching motor loads or power factor correcting capacitors can produce voltage spikes and ringing. Phase controlled rectifier loads and arcing devices produce continuous noise unless adequately filtered. Noise sources are either common mode, which appears between both sides of a power line and ground or of transverse mode, which appears from line to line. HPS Clean Power products, such as our Computer Regulators remove these noise sources.

  • dV/dt reactor – definition
  • What is Dirty Power?

      Dirty power is caused by a number of things. Simply put, dirty power is what causes your radio or telephone to ‘crackle’ during an electrical storm; or what causes ‘snow’ on your TV when someone is using a power tool, sewing machine or other appliances in your house. This dirty power, or electrical noise, is a nuisance when it appears on your radio, TV or telephone. When it gets into your computer, it can cause serious errors; improper readouts, printing problems, or even damage your computers circuit.

  • What is IEEE 1584-2018?

      IEEE 1584-2018 provides mathematical models for designers and facility operators to apply in determining the arc-flash hazard distance and the incident energy to which workers could be exposed during their work on or near electrical equipment.

      It generally indicates that systems with an available short circuit current of 2000 Amps or higher should be assessed for arc-flash potential. A rule of thumb would indicate that most systems fed by a 45 kVA or larger transformer will need to be assessed if impedance (%Z) of 45 kVA is less than 6%, 30 kVA if %Z is less than 4% or 15 kVA if %Z is less than 2%.

  • VAR compensator reactor – definition
  • Which side of the transformer is primary and which side is secondary?

      From the transformer manufacturer’s perspective, the side on the transformer that is initially energized should be considered primary. HPS solar duty transformer identifies the primary side on its nameplate. Energizing the transformer from the secondary side may cause elevated energizing inrush currents that can cause nuisance faults.

  • Do I need a Wye-N connection to supply my solar inverter if it does not need or check for a balanced phase to ground voltage?
  • Why do non-linear loads have low power factors and why is it important to have a high power factor?

      Power factor is a measure of how effectively a specific load consumes electricity to produce work. The higher the power factor, the more work produced for a given voltage and current. Figure 3-1 shows the power vector relationships for both linear and non-linear loads. Power factor is always measured as the ratio between real power in kilowatts (kW) and apparent power in kilovolt-amperes (kVA).

      For linear loads, the apparent power in kVA (S = V•I) is the vector sum of the reactive power in kVAR (Q) and the real power in kW (P). The power factor is P/S = CosΦ, where Φ is the angle between S and P. This angle is the same as the displacement angle between the voltage and the current for linear loads. For a given amount of current, increasing the displacement angle will increase Q, decrease P, and lower the PF. Inductive loads such as induction motors cause their current to lag the voltage, capacitors cause their current to lead the voltage, and purely resistive loads draw their current in-phase with the voltage. For circuits with strictly linear loads (a rare situation) simple capacitor banks may be added to the system to improve a lagging power factor due to induction motors or other lagging loads.

      For non-linear loads, the harmonic currents they draw produce no useful work and therefore are reactive in nature. The power vector relationship becomes 3 dimensional with distortion reactive power, H, combining with both Q and P to produce the apparent power which the power system must deliver. Power factor remains the ratio of kW to kVA but the kVA now has a harmonic component as well. True power factor becomes the combination of displacement power factor and distortion power factor. For most typical nonlinear loads, the displacement power factor will be near unity. True power factor however, is normally very low because of the distortion component. For example, the displacement power factor of a personal computer will be near unity but its total power factor is often in the 0.65 – 0.7 range. The best way to improve a poor power factor caused by non-linear loads is to remove the harmonic currents.

      Most Utilities charge their customers for energy supplied in kilowatt-hours during the billing period plus a demand charge for that period. The demand charge is based upon the peak load during the period. The demand charge is applied by the utility because it must provide equipment large enough for the peak load even though the customer’s average power may be much lower. If the power factor during the peak period (usually a 10 minute sliding window) is lower than required by the utility (usually 0.9), the utility may also apply a low PF penalty charge as part of the demand charge portion of the bill.

      More Harmonic Mitigating Transformer Frequently Asked Questions

  • What is Power Factor or True Power Factor?

      The ratio of real power to apparent power and is:  PF = (Power actually delivered to load) ÷ (RMS Voltage x RMS Current).  Waveform distortion caused by harmonics is included in this calculation.  The worse the phase shift between voltage and current and/or the worse the harmonic distortion, the worse the power factor.  Low power factor cause by either harmonic currents (and a distorted sine wave) or reactive power can increase transformer heating.  If PF is low but DPF is not, adding power factor correction capacitors may not help

      Displacement power factor (DPF) is different.  DPF is the cosine of phase angle between the current and voltage fundamental sine waves.  Low power factor is typically caused by inductive loads such as motors.  Fundamental power factor only looks at the 60 Hz sine wave and does not take into effect harmonic currents.  DPF is most useful for sizing and measuring the effectiveness of power factor correct capacitors.

      If PF is low but DPF is not, harmonics may be causing the problem and adding power factor correction capacitors may not improve either PF or DPF.  Solutions such as harmonic mitigating transformers or line reactors should be considered.

  • How bad can the Dirty Power problem get?

      One form of dirty power usually called a surge can burn out computer, audio, video or nay other electronic circuitry in seconds. A surge is a high voltage pulse riding the normal power wave. Surges will commonly measure 600 to 2500 volts. Even though they occur for only mille-seconds, this is enough time to melt down circuits.

  • How does Dirty Power affect my electronic equipment?

      Your computer operates by reading electronic impulses. Dirty power contains a great number of random pulses riding on the normally smooth surface of a power wave. As these random pulses enter the circuits, your computer ‘reads’ them as data. This can cause a whole range of problems. You may suddenly get garbled numbers or letters in a readout or printout.

      You could loose files, skip program steps, have trouble loading programs or have connection problems while on the Internet.

  • When can you Reverse Connect a transformer?

      In general, distribution transformers can be reverse connected without de-rating the nameplates KVA capacity. However, this is rarely considered in modern applications due to NEC code changes. Several precautions need to be taken for reverse connection of some smaller transformers. These would include:
      Dealing with higher current inrush which can cause nuisance tripping.

      HPS transformers under 6kVA three-phase and 3kVA single-phase, there is a “turns ratio compensation” on the low voltage winding. When backfed the turns compensation actually reduces the output voltage. When a three-phase transformer is reverse connected thus resulting in a Wye-Delta configuration, the neutral terminal must be isolated. This modification may violate the warranty and agency listings such as U.L.

      Back-fed transformers increase the installer’s liability since a future user may not realize what is the primary while de-energizing the transformer.

      In general HPS suggest that a proper step up transformer which is designed with the low voltage terminals as the primary terminal be used.

  • What is a Buck Boost transformer?
  • What is the energy efficiency regulation compliance in the U.S. and Canada?

      In the past several years, there has been an accelerated rate of change in updating energy efficiency standards for transformers in North America.

      Governments in US and Canada are encouraging users to use higher energy efficiency dry-type transformers, to help reduce carbon dioxide emissions. There is also a long term cost savings in operating higher efficiency transformers translated in lower energy usage, lower cooling cost, etc.

      In U.S.A. the Department of Energy (DOE) has mandated new higher efficiency levels effective Jan. 1st 2016.

      In Canada Natural Resources Canada (NRCan) published SOR/2016-311 which amends the Energy Efficiency Act to align the via amendment 14 the minimum energy efficiency levels for dry type transformers to the ones implemented by DOE in Jan 2016.

      The new NRCan 2019 regulation is going to be enforced across Canada on May 1st, 2019. The Ontario government already adopted these new efficiency levels by publishing the ON Reg.404-12 which in schedule 6 defines the new energy efficiency levels that dry type transformers sold in ON must comply with starting Jan.1st 2018 (Ontario Energy Efficiency Compliance).

      The rest of Canada (including Quebec) is still following the current energy efficiency levels prescribed by CSA C802.2, until the new NRCan regulations come in effect on May 1st 2019.

      To help our valued customers in estimating the cost savings resulting from upgrading their old dry type transformer to the new DOE2016/NRCan2019 efficiency levels, HPS has developed an Energy Savings Calculator available on its website. To find out how HPS can help reduce your energy consumption, click here.

      To visit the Canadian Gazette for more information about the Canadian energy efficiency standards, click here.

      For the Ontario Energy efficiency regulation please click here.

      To view an electronic copy of the U.S. DOE energy efficient standards, click here.

  • What is a Dielectric System in a transformer?
  • How are HPS transformers designed to shield against voltage transients?

      Electrostatically shielded transformers may help minimize or limit the effects of voltage transients. Common Mode noise is measured from line to ground and is usually the most troublesome. Transverse Mode noise is measured from line to line. Attenuation is the difference of an incoming transient on the primary of the transformer to the secondary side.

      An electrostatic or Faraday shield is simply a thin piece of grounded non ferrous metal (generally copper foil) placed between the primary and secondary windings of a transformer. The shield extends from the top to the bottom of the windings. Some manufactures use shields that don’t extend the full length of the coil face. While less expensive, they will not offer as much protection as a full shield.

      There is no national standard that gives test methods for measuring CMNA and TMNA. Hence, in the industry, various companies have different claims that they have succeeded in getting into customer or consultant specifications. A lot of the confusion for shielded transformers results from differing claims made by various manufacturers and experts. Some recent reports indicate that and electrostatic shield may have little to no benefit where the secondary is grounded which is in most applications. The difference in the claims results from many variables:

      1. Standard single shielded distribution and drive isolation transformers may theoretically provide typical values of CMNA =60 dB and TMNA = 10 dB.
      2. A single shielded transformer with a low capacitive coupling of less than 30 pF may theoretically provide typical values of CMNA = 100 dB and TMNA = 40 dB.

      A manufacturer should be willing to share their testing procedures and test circuit to verify their
      claims.

      Note attenuation ratings vary by frequency. As the frequency increases, dB ratings go down. The ratings given above may be best case for a wide range of frequencies from 100Hz to 1MHz. Actual attenuation might be significantly higher at the lower frequencies. Some manufactures may claim higher dB’s attenuation by using much lower frequency ranges.

      There may be a large difference between calculated dB and actual dB due to real-life inconsistencies in material and manufacturing. Manufacturers should have actual test data to back up their attenuation claims.

  • What is a Low Voltage General Purpose Transformer?

      HPS’s low voltage general-purpose transformers provide a safe, long lasting, highly reliable power source. They are designed for general lighting and other low voltage applications. They are UL listed and CSA certified.

  • What are the new Energy Efficiency levels coming for Transformers sold in the U.S.?

      Transformers have been and remain an essential part of our electrical infrastructure.  Everywhere we look there is a transformer supplying power to industrial, commercial or residential applications.

      In the past decades the greenhouse gas emissions and the effects on our planet have become the focus of many governments, agencies and individuals. Energy generation is a major contributor to the greenhouse gas emissions. In addition to widespread efforts to make energy generation more environmentally friendly, there is also a goal to lower energy consumption within most industrial, commercial and residential areas. Achieving increased energy efficiency levels for equipment and consumer products has become a priority for many manufacturers.

      Improving the energy efficiency of new transformers is a primary goal of the US Department of Energy (DOE), and they have the legal authority to define efficiency levels and enforce compliance.  Environmentally conscious consumers also recognize that buying a higher energy efficiency transformer will have a societal payback over many years.

      The Department of Energy has established new and more stringent Energy Efficiency levels for Transformers in the U.S. effective January 1st 2016.  The new efficiency levels for Medium Voltage Liquid-Filled, Medium Voltage and Low Voltage Dry-Type Distribution Transformers are defined in DOE’s CFR (Code of Federal Regulations) title 10 part 431.  Widely known as DOE 10 CFR p431, it was published in the Federal Register Vol. 78, No. 75 on Thursday April 18, 2013.  According to the DOE, the new efficiency levels are expected to reduce energy losses by an average of 18% in low-voltage dry-type distribution transformers and 13% for medium-voltage dry-type transformers, over the current TP-1 efficiency levels.

      To put the benefits of this change in perspective, the DOE projects savings up to $12.9 billion in total costs to consumers and 3.63 quadrillion Btu of energy over a 30 year period. In addition, about 265 million metric tons of carbon dioxide emissions will be avoided, equivalent to the annual greenhouse gas emissions of about 52 million automobiles.

      The subject of energy efficiency for transformers raises two main considerations:

      1. Under normal operation a transformer is always on (typically at 35% average loading), making any energy efficiency improvements more significant over an extended period of time.  This means that customers will be rewarded in two manners:  they are reducing greenhouse gas emissions and there is an economic payback through reduced energy costs.  Considering the life expectancy of a transformer and the fact that the transformer will be on 24 hours a day, 7 days a week for the next 25-30 years, even small energy efficiency improvements will pay dividends for decades.  A secondary benefit is that more efficient transformers generate less heat, and in many cases this translates into lower costs to cool the environment in which they are utilized.
      2. The currently mandated energy efficiency levels are already hovering around the 98-99% mark, depending on the type of transformer and ratings.  This means that any further efficiency improvements become more challenging to achieve, typically requiring more and/or better core and conductor materials.  This will directly impact the cost of the transformer in most cases.  However, as noted in point 1 above, there is an economic benefit to offset the higher initial transformer costs.  The new DOE 2016 compliant transformers that will come on the market will also be somewhat heavier than the current TP-1 efficiency level transformers.

      Hammond Power Solutions (HPS) has an online Energy Savings Calculator to help to our customers determine the savings they can achieve by installing a higher efficiency transformer.  It includes a comparison of transformers with older efficiencies to those of higher efficiency (TP1, NEMA Premium and DOE 2016 in the future) as well as specifics of the application and the customer’s cost of energy.

      Currently, for applications that require higher energy efficiency than the DOE regulated TP-1 levels, industry is using Premium Efficiency transformers defined by the NEMA Premium Efficiency Guidelines that stipulate approximately 30% lower loses than the TP-1 levels.  In terms of the environmental benefits of using a NEMA Premium transformer over a TP-1 rated let’s look at an example:

      The Electricity savings resulting from upgrading one three phase 75 kVA transformer can be translated into one of the following:

      • 1.19 Metric Tons of CO2
      • 121 Gallons of Gasoline
      • About 1/6th of the energy used by an average household annually
      • Planting 28 Trees
      • 0.9 Acres of Forest
      • Recycling 0.34 Metric Tons of Waste
      • Savings of $166 per year at $0.12 per kW-Hr

      Forest image 

      At some kVA ratings NEMA Premium energy efficiency levels meet or slightly exceed the DOE 2016 levels, some are slightly below the new requirements.  However, the NEMA Premium products are optional within the market today, and many consumers do not take advantage of the benefits they afford.  Hence, the DOE will require that all transformers manufactured after January 1st, 2016 will meet the new efficiency levels.

      The environmental impact and savings for our customers resulting from the DOE changes are positive and significant.  HPS fully embraces and supports this change, and the environmental benefits our society will receive as a result.  We proudly offer high quality transformers meeting the most stringent Energy efficiency requirements today and will be in a position to support the migration to the new DOE 2016 higher-efficiency designs for our valued partners and customers, beginning in the latter half of 2015.

  • Can a transformer be back-fed or used in reverse?

      In general, distribution transformers can be reverse connected without de-rating the nameplates KVA capacity. However, this is rarely considered in modern applications due to NEC code changes. Several precautions need to be taken for reverse connection of some smaller transformers. These would include:
      Dealing with higher current inrush which can cause nuisance tripping.

      HPS transformers under 6kVA three-phase and 3kVA single-phase, there is a “turns ratio compensation” on the low voltage winding. When backfed the turns compensation actually reduces the output voltage.
      When a three-phase transformer is reverse connected thus resulting in a Wye-Delta configuration, the neutral terminal must be isolated. This modification may violate the warranty and agency listings such as U.L.

      Back-fed transformers increase the installer’s liability since a future user may not realize what is the primary while de-energizing the transformer.

      In general HPS suggest that a proper step up transformer which is designed with the low voltage terminals as the primary terminal be used.

  • New Energy Efficiency levels US 2016

      Transformers have been and remain an essential part of our electrical infrastructure.  Everywhere we look there is a transformer supplying power to industrial, commercial or residential applications.

      In the past decades the greenhouse gas emissions and the effects on our planet have become the focus of many governments, agencies and individuals. Energy generation is a major contributor to the greenhouse gas emissions. In addition to widespread efforts to make energy generation more environmentally friendly, there is also a goal to lower energy consumption within most industrial, commercial and residential areas. Achieving increased energy efficiency levels for equipment and consumer products has become a priority for many manufacturers.

      Improving the energy efficiency of new transformers is a primary goal of the US Department of Energy (DOE), and they have the legal authority to define efficiency levels and enforce compliance.  Environmentally conscious consumers also recognize that buying a higher energy efficiency transformer will have a societal payback over many years.

      The Department of Energy has established new and more stringent Energy Efficiency levels for Transformers in the U.S. effective January 1st 2016.  The new efficiency levels for Medium Voltage Liquid-Filled, Medium Voltage and Low Voltage Dry-Type Distribution Transformers are defined in DOE’s CFR (Code of Federal Regulations) title 10 part 431.  Widely known as DOE 10 CFR p431, it was published in the Federal Register Vol. 78, No. 75 on Thursday April 18, 2013.  According to the DOE, the new efficiency levels are expected to reduce energy losses by an average of 18% in low-voltage dry-type distribution transformers and 13% for medium-voltage dry-type transformers, over the current TP-1 efficiency levels.

      To put the benefits of this change in perspective, the DOE projects savings up to $12.9 billion in total costs to consumers and 3.63 quadrillion Btu of energy over a 30 year period. In addition, about 265 million metric tons of carbon dioxide emissions will be avoided, equivalent to the annual greenhouse gas emissions of about 52 million automobiles.

      The subject of energy efficiency for transformers raises two main considerations:

      (1) Under normal operation a transformer is always on (typically at 35% average loading), making any energy efficiency improvements more significant over an extended period of time.  This means that customers will be rewarded in two manners:  they are reducing greenhouse gas emissions and there is an economic payback through reduced energy costs.  Considering the life expectancy of a transformer and the fact that the transformer will be on 24 hours a day, 7 days a week for the next 25-30 years, even small energy efficiency improvements will pay dividends for decades.  A secondary benefit is that more efficient transformers generate less heat, and in many cases this translates into lower costs to cool the environment in which they are utilized.

      (2) The currently mandated energy efficiency levels are already hovering around the 98-99% mark, depending on the type of transformer and ratings.  This means that any further efficiency improvements become more challenging to achieve, typically requiring more and/or better core and conductor materials.  This will directly impact the cost of the transformer in most cases.  However, as noted in point 1 above, there is an economic benefit to offset the higher initial transformer costs.  The new DOE 2016 compliant transformers that will come on the market will also be somewhat heavier than the current TP-1 efficiency level transformers.

      Hammond Power Solutions (HPS) has an online Energy Savings Calculator to help to our customers determine the savings they can achieve by installing a higher efficiency transformer.  It includes a comparison of transformers with older efficiencies to those of higher efficiency (TP1, NEMA Premium and DOE 2016 in the future) as well as specifics of the application and the customer’s cost of energy.

      Currently, for applications that require higher energy efficiency than the DOE regulated TP-1 levels, industry is using Premium Efficiency transformers defined by the NEMA Premium Efficiency Guidelines that stipulate approximately 30% lower loses than the TP-1 levels.  In terms of the environmental benefits of using a NEMA Premium transformer over a TP-1 rated let’s look at an example:

      The Electricity savings resulting from upgrading one three phase 75 kVA transformer can be translated into one of the following:

      • 1.19 Metric Tons of CO2
      • 121 Gallons of Gasoline
      • About 1/6th of the energy used by an average household annually
      • Planting 28 Trees
      • 0.9 Acres of Forest
      • Recycling 0.34 Metric Tons of Waste
      • Savings of $166 per year at $0.12 per kW-Hr

      Dense Forest

       

      At some kVA ratings NEMA Premium energy efficiency levels meet or slightly exceed the DOE 2016 levels, some are slightly below the new requirements.  However, the NEMA Premium products are optional within the market today, and many consumers do not take advantage of the benefits they afford.  Hence, the DOE will require that all transformers manufactured after January 1st, 2016 will meet the new efficiency levels.

      The environmental impact and savings for our customers resulting from the DOE changes are positive and significant.  HPS fully embraces and supports this change, and the environmental benefits our society will receive as a result.  We proudly offer high quality transformers meeting the most stringent Energy efficiency requirements today and will be in a position to support the migration to the new DOE 2016 higher-efficiency designs for our valued partners and customers, beginning in the latter half of 2015.

  • how Line Reactor eliminate Nuisance Tripping

      Transients due to switching on the utility line and harmonics from the drive system can cause intermittent tripping of circuit breakers. Furthermore, modern switchgear, equipped with solid-state trip sensing devices, is designed to react to peak current rather than RMS current. As switching transients can peak over 1000 volts on a 600 volt system, the resulting over-voltage will cause undesirable interruptions.

      A reactor added to your circuit restricts the surge current by utilizing its inductive characteristics and mitigates nuisance tripping. The impedance of a transformer will have similar effects.

      Learn about HPS Centurion R Reactors

  • Capacitor switching reactor – definition
  • What is ANSI C57.12.91?
  • What is ANSI C57.12.51?

      IEEE Standard for Ventilated Dry- Type Power Transformers, 501 kVA and Larger, Three-Phase, with High- Voltage 34.5 kV to 601 V and Low- Voltage 208Y/120 V to 4160 V covering General Requirements. The current standard was updated in 2008.

      This standard is intended to set forth characteristics relating to performance, limited electrical and mechanical interchangeability, and safety of the equipment described, and to assist in the proper selection of such equipment. Specific rating combinations are described in the range from 750/1000 to 7500/10 000 kVA inclusive, with high-voltage 601 to 34 500 volts inclusive and low-voltage 208Y/120 to 4160 volts inclusive. Part I of this standard describes certain electrical and mechanical requirements and takes into consideration certain safety features of 60-Hz, two-winding, three-phase, ventilated dry-type transformers with self-cooled ratings 501 kVA and larger, generally used for step-down purposes. Part Il describes other requirements or alternatives which may be specified for some applications and lists forced-air-cooled ratings for certain sizes.

  • What is an air terminal chamber (ATC) or line terminal compartment?

      This is an air filled terminal compartment, typically 12″-24″ wide that is bolted to one or both sides of a substation transformer. This typically contains either the primary or secondary connections with a steel barrier separating it from the larger chamber containing the actual transformer core and coil. The ATC may also contain additional connections for loop feeds and/or lightning arresters.

  • Air core motor starting reactor – definition
  • What are dust filters?

      Dust filters are placed over ventilation openings to mitigate dust accumulation within the transformer’s enclosure. Filters are typically made to be removable and washable. Care must be taken for regular maintenance since accumulating dust will limit airflow and reduce air cooling. For this reason, dust filters are typically avoided through using non-ventilated designs or moving the transformer’s location. Because of reduced airflow, transformers cannot be retrofitted with dust filters without derating or using fan forced venting.

  • What are solar transformers?

      Solar transformers covers a broad selection of transformers which are designed for the unique requirements of a solar power system. These transformers can include solar inverter transformers, grid tie transformers and zig-zag autotransformers or isolation transformers specially designed to be used in grounding banks for utility hook-ups. Transformers used to directly deliver power to utilities must often be capable of bidirectional current flow.

  • What is an incoming line interrupter switch (electrical disconnect)?

      This is typically a two position, three phase switch designed to disconnect a transformer on the line side. The switch may or may not also have fuses. The switch assembly is typically attached directly to the transformer enclosure and electrically connected through close coupled bussing.

  • What is a solar grounding bank?
  • What is a pad mounted transformer?

      A pad mounted transformer typically refers to a specific style of enclosure for larger transformers that is capable of being installed in areas accessible to the general public. The transformer will typically have features including tamper resistant construction, tamper proof bolts and screws, lockable compartments with hinged doors, bottom entry of primary and secondary cabling and baffled ventilation openings if applicable. These should not be confused with the general statement that electrical transformers are often installed on a concrete pad.

  • What is NEMA ST 20?
  • What are Medium Voltage Transformers and where are they used?

      Medium voltage transformers that have one or more windings above 1.2 k-volts. Ventilated medium voltage transformers up to 2500 kVA are covered by DOE 2016 efficiency regulation in the U.S.A. and up to 5000 kVA by NRCan 2019 efficiency regulations in Canada.

      They are primarily for use in stepping down medium voltage power to a lower operating voltage for commercial, institutional or industrial applications. However, medium voltage transformers may also be used to step-up voltage.

  • What does is a reconnectable transformer?

      A reconnectable transformer typically refers to a transformer with two primary connections. These may be used for mobile equipment, test transformers or to accommodate future voltage changes and upgrades in a facility without having to change the transformer. Depending on the difference in voltages and application reconnectable transformers may be exempt from current efficiency regulations.

  • What does LV stand for?
  • What is a Unit Substation Style Transformer (USST)?
  • What is U.L. 1562?

      U.L. 1562 covers medium voltage dry-type transformers:

      1.1 These requirements cover single-phase or three-phase, dry-type, distribution transformers, including solid cast and resin encapsulated transformers. The transformers are provided with either ventilated or non-ventilated enclosures and are rated for a primary or secondary voltage from 601 to 35000 V.

      1.2 These transformers are intended for installation in accordance with the National Electrical Code, ANSI/NFPA 70.

      1.3 These requirements do not cover the following transformers:

      1. Instrument transformers
      2. Step-voltage and induction voltage regulators
      3. Current regulators
      4. Arc furnace transformers
      5. Rectifier transformers
      6. Specialty transformers (such as rectifier, ignition, gas tube sign transformers, and the like)
      7. Mining transformers
      8. Motor-starting reactors and transformers

      1.4 These requirements do not cover transformers under the exclusive control of electrical utilities utilized for communication, metering, generation, control, transformation, transmission, and distribution of electric energy regardless of whether such transformers are located indoors, in buildings and rooms used exclusively by utilities for such purposes; or outdoors on property owned, leased, established rights on private property or on public rights of way (highways, streets, roads, and the like).

  • What is U.L. 1561?

      UL1561 covers 600 Volt Class Transformers:

      1.1 These requirements cover:

      1. General purpose and power transformers of the air-cooled, dry, ventilated, and non-ventilated types to be used in accordance with the National Electrical Code, ANSI/NFPA 70. Construction types include step up, step down, insulating, and autotransformer type transformers as well as air-cooled and dry-type reactors

      OR

      1. General purpose and power transformers of the exposed core, air-cooled, dry, and compound-filled types rated more than 10 kVA to be used in accordance with the National Electrical Code, ANSI/NFPA 70. Constructions include step up, step down, insulating, and autotransformer type transformers as well as air-cooled, dry, and compound-filled type reactors.

      1.2 These requirements do not cover ballasts for high intensity discharge (HID) lamps (metal halide, mercury vapor, and sodium types) or fluorescent lamps, exposed core transformers, compound-filled transformers, liquid-filled transformers, voltage regulators, general use or special types of transformers covered in requirements for other electrical equipment, autotransformers forming part of industrial control equipment, motor-starting autotransformers, variable voltage autotransformers, transformers having a nominal primary or secondary rating of more than 600 volts, or overvoltage taps rated greater than 660 volts.

      1.3 These requirements do not cover transformers provided with waveshaping or rectifying circuitry. Waveshaping or rectifying circuits may include components such as diodes and transistors. Components such as capacitors, transient voltage surge suppressors, and surge arresters are not considered to be waveshaping or rectifying devices.

  • What is ANSI C57.12.01?
  • What is rodent screening?

      Rodent screens are added over ventilation openings of transformers to prevent rodents from entering the compartment. Large transformers installed directly on concrete pads may also need a steel bottom added. Rodent screens will not prevent the entry of dust or insects.

  • RC filter reactor – definition
  • What are High Voltage and Low Voltage windings?
  • What are the most common power problems?
  • What is the induction principle of transformers?

      A transformer consists of laminated silicon steel cores on which one or more coils of wire have been wound. The two windings are electrically isolated from each other (with the exception of autotransformers) and usually have widely different numbers of turns.

      If the transformer primary is connected to an A.C. power source of suitable voltage, a small no-load current called the exciting current will flow into the coil and produce a magnetic flux in the iron core. Since the source is A.C., the flux will also be alternating. This alternating magnetic flux links the secondary turns and induces a small voltage in each turn. The induced volts per turn of the secondary windings adds to appear across the secondary terminals. It should be understood that the flux induces a voltage in each primary turn equal to that in each secondary turn. The difference between the total induced primary voltage and the applied voltage is approximately equal to the IR drop. The ratio of turns between the primary and secondary coils determines the output voltage.

  • Should low voltage system be assessed for arc-flash hazards?

      IEEE 1584-2018 provides mathematical models for designers and facility operators to apply in determining the arc-flash hazard distance and the incident energy to which workers could be exposed during their work on or near electrical equipment.

      It generally indicates that systems with an available short circuit current of 2000 Amps or higher should be assessed for arc-flash potential. A rule of thumb would indicate that most systems fed by a 45 kVA or larger transformer will need to be assessed if impedance (%Z) of 45 kVA is less than 6%, 30 kVA if %Z is less than 4% or 15 kVA if %Z is less than 2%.

  • Are Harmonic Mitigating Transformers (HMT’s) available in medium voltage configurations?
  • What is considered Low Voltage for distribution transformers?

      The term “Low Voltage” for electrical distribution transformers can refer to different voltages. Generally transformers with primary and secondary voltages at or below 600 volts are considered “Low Voltage”.

      • 690 Volts is sometimes considered low voltage. It is sometimes referred to as a 600/690 volt system.
      • The National Electric Code considers voltages <1000 volts to be low voltage.
      • Some regulatory agencies consider 1.2 kV and below to be low voltage.

      As a result there is some market confusion for voltages between 600 and 1200 volts with some regulations having a definition gap for some of these voltages.