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Recent laws enacted in the states of Massachusetts and Minnesota legislate the use of high efficiency distribution transformers in commercial and industrial facilities; other states are expected to follow. The impetus for such dramatic measures is the promise of reduced energy utilization. In addition to lowering operating costs, lower energy utilization can reduce the need for infrastructure overbuilding and result in less greenhouse gas emissions, making a substantial contribution toward a cleaner environment.

Since there appear to be numerous benefits accrued from the use of higher efficiency transformers, why wouldn’t every good corporate citizen rise to the occasion and do our planet some good? Why is legislation required?

Traditional buying patterns reflect a strong preference for first cost, the responsibility for which usually rests with the electrical contractor. The purchase of more energy efficient products requires a shift in the buying process where life cycle cost analysis includes ongoing operating costs as well as upfront capital costs. The implementation of a legislative strategy may require a rethinking of the buying process associated with the construction process for commercial and industrial transformers.

This article will examine some of the issues relating to the transition to the use of energy efficient transformers.

Energy and Environmental Goals
Simply put, high efficiency transformers consume less power doing a similar job as a more conventional, less efficient transformer. Lower power consumption translates into a lower energy bill for the consumer and, therefore, less total power generation is required. From an environmental perspective, less power generation reduces as the need to burn coal (and other fossil fuels) lessens, which in turn reduces greenhouse gases emissions. A reduced requirement for power generation reduces the need for infrastructure overbuilding. In the big picture, the air becomes cleaner, we have a better place to live, and we become more competitive internationally as our costs of goods and services become more economical. This scenario seems like a win, win proposition.

Background –How are transformer inefficiencies or losses derived?
Transformers are not perfect energy transfer vehicles. Their inefficiencies fall into two categories: No load (or core) losses and load losses.

• No load losses relate to the cost of powering the magnetic circuit of the transformer, which enables the transfer of power. As such, no load losses are incurred 24 hours a day, 7 days a week, for as long as the transformer is energized even when load is connected. Typically, no load losses are higher for low cost transformers, K-rated transformers and low temperature rise transformers. Also, losses tend to increase with the rating of the transformer. These losses predominate when the transformer is lightly loaded.

• Load losses relate to the windings losses. These vary with the square of load current. Because of this mathematical relationship, load losses increase rapidly as a transformer is loaded and represent most of the total losses when the transformer is heavily loaded.

Transformer losses and efficiency data are readily available from the various manufacturers, but it should be noted that the data applies to linear loading. Yearly operating cost is calculated by multiplying kW losses by the hours/year usage and cost of power (kWh and Demand). What is not well understood is the negative impact modern electronic loads (nonlinear) have on transformer efficiency. Transformers feeding computers and other electronic equipment see their losses increase dramatically (more on this later).

Required efficiency levels – NEMA TP-1
To date, the laws either in place or under consideration refer to NEMA Standards Publication TP-1-1996 "Guide for Determining Energy Efficiency for Distribution Transformers," specifically to the minimum efficiency levels contained in Tables 4-1 and 4-2, with "distribution transformer" being defined as transformers having primary voltage of 34.5 kV or below and secondary voltages of 600 volts and below.

Figure 1. Excerpt for three phase efficiency from Table 4-2 NEMA CLASS 1 EFFICIENCY LEVELS FOR DRY-TYPE DISTRIBUTION TRANSFORMERS

Photo 1. Dry type standard 30 kVA transformer with NEMA 3-R rainshield installed outdoors.

NEMA TP-1 and the EPA ENERGY STAR® Commercial & Industrial (C&I) Transformer Program
In its quest to identify opportunities to reduce greenhouse gas emissions, the EPA identified that commercial and industrial distribution transformers account for somewhere between 60 and 80 billion kWh of losses each year. These losses translate into 9 days of US power generation, resulting in substantial associated smokestack emissions. The ENERGY STAR C&I distribution transformer program is an extension of what is already a very successful program. The ENERGY STAR logo program is a recognized symbol of energy savings (you see it on copiers and computer monitors) and is administered by the US Environmental Protection Agency (EPA). The minimum transformer efficiency levels match those in NEMA TP-1. This EPA program raises the level of public awareness that the transformer is a source of substantial energy losses and associated pollution, and provides a positive association for manufacturers who partner with the EPA and deliver compliant products bearing the ENERGY STAR logo.

Effect of electronic equipment on transformer efficiency & power quality
IMPORTANT: Today’s transformer testing standards call for loss testing under resistive (ideal linear) loading. This is the traditionally accepted approach. Today electronic or nonlinear loading is the reality. Actual transformer losses under real-world loads like today’s electronic office equipment (personal computers, printers, etc.) have clocked in at almost triple those from factory tests using standard resistive loads. The difference stems from the harmonics (higher frequency currents) produced by the large and ever increasing quantities of electronic equipment we are connecting to our electrical systems today. The energy story is even more acute when the cost of cooling is considered and accounted for as a result of this harmonic-rich load.

Since the whole point of the electrical system is to deliver decent power to the connected loads, the transformer can play a make or break role in determining the level of power quality and efficiency in the system. Both can be achieved together. For example, Powersmiths International Corporation’s K-Star transformer has been independent performance validated by the US DOE to hold 98% efficiency under computer-type loading while delivering substantial harmonic reduction.

Figure 3. Power Quality Institute Energy Savings and payback Calculator

Photo 2. NEMA TP-1 Energy STAR compliant, K-Star harmonic cancellation transformer (courtesy of Powersmiths International Corp.)

Ironically, NEMA TP-1 exempts transformers designed for high harmonics from having to meet its efficiency targets. So policy and reality seem to diverge with respect on this matter.

Who will feel the impact of NEMA TP-1 and Harmonic Correcting Energy Efficient Tranformers?

• The Buyer
The ultimate buyer of these products may or may not be familiar with transformers and the associated operating cost. For example, if the buyer is an owner/operator, then the case for life cycle costing and return on investment usually makes sense. For property managers, first cost may be the key buying decision criteria. Because these products typically cost more up-front, it is important to understand the buyer’s motivation. Understanding the buyer’s motivation will go a long way.

• The Facilities Energy Auditor will have a keen interest in these products because it falls within the mandate of reducing power consumption.

• The Environmental Coordinator benefits from the less tangible but global "greening" associated with reduced smokestack emissions due to the reduction in power consumption.

• The Electrical Consulting Engineer, in conjunction with the building architect, can offer the client clean, more reliable power and a lower operating cost.

• The Electrical Inspector will be required to inspect every transformer installation to ensure that the labeling reflects the new efficiency levels. The inspector will have to be educated to a precise course of action in case of nonconformance with any laws in place.

• The Electrical Contractor will be asked in many cases to supply a three year life cycle cost for a proposed solution. This will provide the client with the necessary information to make an informed decision where legislation is not enacted.

Question: Less clear is who bears the liability if a non-compliant product is installed? One or more of the above? Stay tuned as state laws are enacted.

Education – The Key
• Given that the transformer is tucked away in a small electrical room and requires next to no maintenance, its impact in terms of losses and power quality is not well understood.

• While efficiency standards such as NEMA TP-1 (sometimes with legal teeth), environmental programs such as the EPA ENERGY STAR C&I transformer program, and harmonic standards such as IEEE-519 exist, they must be explained in terms that make financial sense.

• Appreciation for a Total Ownership Cost model for determining transformer purchasing, one that includes both up-front and operating cost, is a must if the entrenched first cost purchase decision is to be displaced.

The key is education. The opportunity for savings, better power quality and environmental benefits is bigger than we can imagine, but the story has to be told to everyone. We all stand to win.

Further Reading
NEMA Standards Publication TP-1-1996 "Guide for Determining Energy Efficiency for Distribution Transformers"

• www.pqi.com 

• www.epa.gov/energystar 

• www.epa.gov/ASAP 

• www.eren.doe.gov/femp/procurement/trans.html 

• www.powersmiths.com 

• www.squared.com 

Philip Ling is a licensed electrical engineer. He has been active in the field of harmonic cancellation for the past ten years, publishing over two dozen papers and presenting at technical power quality conferences across North America, addressing such topics as high neutral current and efficiency of systems under nonlinear load. Most recently he has focused on designing very high efficiency transformers that hold their efficiency when feeding the electronic equipment found in today’s office environment.

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