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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%.

  • 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 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

  • 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.

  • 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 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
  • 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).

  • 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 communication options come with the HPS TruWave Active Harmonic Filter
  • What does AHF stand for
  • 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.

  • 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 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:

       

  • Line reactor – definition
  • Iron core filter 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.

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

  • 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.

  • 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?
  • 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.

  • 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).

  • What is ANSI NETA ATS-2017?
  • Does HPS have NRTL certification?
  • 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 exciting or excitation current?

      A transformer exciting current is the current or amperes required to energize the core. Even with zero load, a transformer will draw a small amount of current due to internal loss. The excitation current is made up of two components. The real component in the form of losses that are commonly referred to as no-load losses. The second form is reactive power measured in KVAR.

  • What is a solar grounding bank?
  • What is NEMA ST 20?
  • What is NFPA (National Fire Protection Association)?

      The National Fire Protection Association (NFPA) is a United States trade association, albeit with some international members, that creates and maintains private, copyrighted standards and codes for usage and adoption by local governments.

      NFPA 70E covers the Standard for Electrical Safety in the Workplace.

  • What does Readily Accessible mean?

      Per 1.2.2 of NEMA ST-20, Capable of being reached quickly for operation, renewal, or inspections, without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, chairs, etc.

  • 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 ANSI C57.12.01?
  • 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.

  • 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.

  • When Using a Two or Three Contactor Bypass with a Variable Frequency Drive, Where Should the Input and Output Line Reactors be located?
  • What is Voltage Regulation?

      Voltage regulation is the difference between the transformer secondary No-Load and Full-Load voltage with respect to its Full-Load voltage.  Essentially, every transformer has a voltage drop caused by its own impedance (which is composed of its winding resistive and inductive properties).  Therefore, at different voltages and loading conditions, this internal voltage drop across the transformer windings will vary and ultimately will affect the final secondary output voltage.

  • What is Zone Classification?

      Obsolete versions of seismic standards used to classify seismic areas ranging from zone 0 to zone 4, where zone 0 indicates the weakest earthquake ground motion and zone 4 indicates the strongest. The zone classification is no longer used. The current standards specify the Sds design earthquake spectral response acceleration parameter as described above.

      Please refer link https://seismicmaps.org/ to determine the Sds criteria for a specific location.

  • Who Needs Seismic?

      Healthcare facilities and emergency response locations, including police stations and other vital government facilities, will often include a Seismic Certification requirement. Power generation stations may also have this requirement as well as facilities handling hazardous, toxic or explosive materials.

      To determine the Sds criteria for a specific location, the U.S. Geological Survey provides a utility on their website, which can be viewed at https://seismicmaps.org/

  • What is NFPA 70E?

      NFPA 70E is the titled Standard for Electrical Safety in the Workplace, is a standard of the National Fire Protection Association (NFPA). The document covers electrical safety requirements for employees. The NFPA is best known for its sponsorship of the National Electrical Code (NFPA 70).

      NFPA 70E addresses employee workplace electrical safety requirements. The standard focuses on practical safeguards that also allow workers to be productive within their job functions. Specifically, the standard covers the safety requirements for the following:

      • Electrical conductors and equipment installed within or on buildings or other structures, including mobile homes, recreational vehicles, and other premises (yards, carnivals, parking lots, and industrial substations)
      • Conductors that connect installations to a supply of electricity
      • Not covered are – electrical installations in marine, aircraft, auto vehicles, communications and electrical utilities.

      Key principles covered are JSA/JHA/AHA procedures to ascertain shock protection boundaries, arc flash incident energy expressed in calories/cm2, lockout-tagout, and personal protective equipment. While the various OSHA, ASTM, IEEE and NEC standard provide guidelines for performance, NFPA 70E addresses practices and is widely considered as the de facto standard for Electrical Safety in the Workplace.

  • How are Seismic Units Rated?

      Three criteria are typically defined for seismic units:  Sds, Ip, z/h.

      Sds = Design earthquake spectral response acceleration parameter at short periods (ASCE 7-16 Section 11.4.4 Design Spectral Acceleration Parameters).  The required motion coefficient is dependent on the facility’s location and soil type. Most of the United States requires Sds = 0.05 to 1.5g. Specific regions require an Sds = 2.0g such as along the Missouri state line south of Illinois and parts of California.

      Ip = Component Importance Factor (ASCE 7-16 Section 13.1.3 Component Importance Factor).  Ip is dependent on the function of the building in which the transformer is installed. Typically, an Ip is assumed to equal 1.5 for transformers expected to function continuously through and after an earthquake.

      z/h = A ratio of the height in the structure that the component has been anchored, to the overall height of the structure.  A value of z/h of 1.0 states that the component is capable of being installed anywhere within the structure (ASCE 7-16 Section 13.3.1 Seismic Design Force).

      z/h - a ratio of the height of the structure

  • What is Seismic Certified?

      A fair amount of construction projects require components to be “Seismic Certified.” A Seismic Certification ensures the component will withstand and operate after an event such as an earthquake. In addition to requiring structural components to meet specific seismic regulations, most jurisdictions also require non-structural components – including electrical systems – to be “Seismic Certified.”

      Seismic requirements are defined by the International Building Code 2018 and the California Building Code (2019). ASCE 7-16 is the base standard for many building codes, and is referenced by both IBC and the CBC.

      OSHPD, the Office of State-wide Health Planning and Development, requires actual “shake-testing” of products prior to allowing products to be specified for construction or retrofit projects anywhere in the state of California. This testing must be reviewed by a California state certified structural engineer. Without a widespread nationwide approval process, many other jurisdictions require the OSHPD Special Seismic Certification Preapproval (OSP) for projects.

  • Do HPS transformers conform to the NEC 451-10 grounding requirements?

      All HPS enclosed transformers and reactors can be installed to be compatible with the NEC 451.10 grounding requirements.

      A) Dry-Type Transformer Enclosures. Where separate equipment grounding conductors and supply-side bonding jumpers are installed, a terminal bar for all grounding and bonding conductor connections shall be secured inside the transformer enclosure. The terminal bar shall be bonded to the enclosure in accordance with 250.12 and shall not be installed on or over any vented portion of the enclosure.

      Exception: Where a dry-type transformer is equipped with wire-type connections (leads), the grounding and bonding connections shall be permitted to be connected together using any of the methods in 250.8 and shall be bonded to the enclosure if of metal.

      HPS ventilated low-voltage transformers are typically supplied with pre-installed grounding bars or lugs. If the unit does not have pre-installed lugs, the enclosure is compatible for the user to install the required lugs in accordance with NEC 250.12. It is the installer’s final responsibility to determine if the final installation complied with local code requirements.

  • What is a vault room?

      A vault room is a reinforced concrete structure used for the purpose of housing liquid cooled transformers, switchgear and other electrical distribution equipment. Requirements for vault rooms for liquid filled transformers are defined by many specifications including NEC 450.26. Vault requirements are outlined in NEC 450, Part III, beginning with 450.4. Typical requirements might include:

      • Ventilation with outside air via a dedicated ductwork
      • Three hour fire-resistant construction including a minimum 4″ concrete floor
      • Oil containment capable of containing the entire liquid contents of the largest transformer
      • Some exceptions will allow lower construction standards such as the use of sprinklers, carbon dioxide or halon systems and/or the use of “less flammable” liquids.

  • What is the International Building Code?

      The International Building Code (IBC) is a model building code developed by the International Code Council (ICC). It has been adopted for use as a base code standard by most jurisdictions in the United States. The IBC addresses both health and safety concerns for buildings based upon prescriptive and performance related requirements. The IBC is fully compatible with all other published ICC codes. The code provisions are intended to protect public health and safety while avoiding both unnecessary costs and preferential treatment of specific materials or methods of construction.

  • What type of transformers does the NEC 2017 require a 1 hour fire seperation barrier?

      A 1 hour fire separation barrier is required for any dry type transformer over 112.5 kVA with less than class 155C insulation. As a practical matter, few dry type transformers in this size range utilize insulation systems below 155C. The most common insulation type is 220C.

      The 1 hour fire separation requirement would also apply to liquid-filled transformers specified in Article 450 based on the type of liquid used and other ratings.