Improved efficiency distribution transformers are available for use in the industrial and commercial sectors. Existing efficiency standards cover three-phase low and medium voltage liquid and dry-type transformers.
Most of the electricity used in commercial and industrial facilities flows through distribution transformers on the customer side of the meter. Commercial buildings often have one or more low voltage distribution transformers on each floor to supply power for plug loads, lighting, HVAC, and other building systems. These distribution transformers are energized 24 hours per day, 365 days per year. Improved efficiency (Tier 1) transformers are now available from many manufacturers.
Transformer efficiency has been improved through changes in design, core or winding material selection, and in the type and amount of insulation used in the transformer. Higher grade steel in the core and more copper in the windings improve efficiency. Amorphous metal reduces core losses when compared with silicon steel. Multiple core designs have evolved that allow for powering down unneeded sections of the transformer core. The Consortium for Energy Efficiency (CEE) identified two efficiency tiers: Tier 1 yields a 35% reduction in total losses (fixed losses plus variable losses) while Tier 2 results in a roughly 50% reduction in losses compared to federal minimum standard level as the baseline.
Even small incremental improvements in transformer efficiency result in significant energy savings. CEE calculated the energy savings of Tier 1 and 2 transformers relative to baseline transformers. Savings range from 414 kWh/year for a 15 kVA Tier 1 transformer to over 21,100 kWh/year for a 1000 kVA Tier 2 unit. Getting these new improved efficiency transformers into service is difficult as transformers have an average useful life of 30 years.
Status:
Baseline Description: 1500 kVA Three-Phase Medium Voltage Dry-Type Transformer Baseline Energy Use: 51198 kWh per year per unit
The energy use is for a 1500 kVA medium voltage dry-type transformer serving a load of 500 kW. The old base case transformer has an efficiency of 98.8% at its 50% load point. The baseline "energy use" is expressed in terms of annual energy losses. (Note: the loss term can be expressed as 31.1 kWh/kVA).
"Typical" Savings: 35% Low and High Energy Savings: 35% to 36% Energy Savings Reliability: 5 - Comprehensive Analysis
To determine energy savings, we must know the efficiency of old, standard efficiency transformers as well as the performance of state-of-the art units. The efficiency values at 50% of rated load are given in Table #1 for old standard efficiency transformers, for NEMA Class 1 transformers (as defined in NEMA Standard TP-1 of 1996), and for transformers that meet the DOE’s new Energy Conservation Standards for Distribution Transformers. DOE’s minimum efficiency standards Final Rulemaking was issued on April 18th, 2013 and applies to all three-phase, medium-voltage dry type distribution transformers manufactured for sale or imported into the U.S. after January 1st, 2016.
Table #1 Transformer Efficiency over Time (medium voltage, dry-type)
kVA Rating Base Case Transformer DOE EPCA Transformer Efficiency 150 97.9 98.6
500 98.4 98.96
1500 98.8 99.22
Assuming that a 1500 kVA transformer is serving a 500 kW load, the old base case transformer has an efficiency of 98.8% with losses equivalent to 51,198 kWh/year. The new DOE EPCA compliant transformer has full load efficiency of 99.22% and reduces losses to 34,433 kWh/year, a reduction of 35.3%.
Energy Use of an Emerging Technology is based upon the following algorithm. Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.