Low Voltage Dry Type Transformers

1
Low Voltage Dry Type Transformers

• CONSORTIUM FOR ENERGY EFFICIENCY
• June Program Meeting
• Nelly Leap
• Electrical Engineer
• Bonneville Power Administration
• June 13-14, 2007
• Boston, Massachusetts

2
Introduction

• Congress established NEMA TP-1 as the
  minimum-efficiency standard via EPAct 2005.
• Low voltage dry-type transformers are required by
  EPAct of 2005 to meet the NEMA TP-1 efficiency
  standard.
• As of January 2007, all transformers produced for
  use in the United States need to meet those
  standards. Transformers produced before that
  date still may be sold.
• NEMA TP-1 (Energy Star) is Level 1 efficiency
  standard.
• Higher-efficiency transformers level 2,3,4, or
  5/6 are not commercially available.

3
Rebate for Commercial and Industrial Low Voltage
Transformers

• BPA will offer incentives under the industrial
  and commercial programs to encourage early
  replacement of older transformers and upgrades to
  higher efficiency transformers (level 2,3,4 or
  5/6).
• Very small energy efficiency improvements can
  equal large kWh savings over the life of the
  transformer. This is because of the large number
  of transformers in near-constant use.
• Based on 1992 FERC data, there were at least
  769,000 transformers in BPAs region (average
  size 80 KVA, average number of customers per
  transformer 3).

4
Transformer Application

• Low voltage transformers step down 480V to
• 277V for lighting systems
• 208V (3 phase) and 120V (single phase) for plug
  load, task lights, computers, printers,
  refrigerators and small equipment.

5
Rebate Deemed Calculation for C and I
Transformers (TRC calculator)

• The rebate calculation requires
• Annual kWh savings, based on differences in
  losses
• Project cost
• Measure life in years (typically the life of a
  building or 30 years)
• Load profile based on flat load or better
  measurements.

6
Cost Effectiveness

• The rebate calculation must satisfy the
  Benefit-Cost (B/C) ratio criteria
• B/C gt 1 -- the measure is cost-effective
• B/C lt 1 -- the measure is not cost-effective

7
kWh Savings for CI Transformers

• Savings are based on the difference in losses
  between the standard transformer with low
  purchase price and higher priced transformers
  (level 1,2,3,4 or 5/6 efficiency standards).
• TP-1 (Level 1) standard has higher energy
  efficiency in the form of less core and winding
  losses.

8
Determine Energy Losses

• Core and winding losses (at full capacity) are
  nameplate data.
• User must provide the average load (in percent of
  nameplate capacity) to determine the winding
  losses.
• Total Losses (kW)

Core losses (watts) ( Load)2 Winding
Losses at Full Capacity (watts) 8760/1000
9
NYSERDA Study

• NYSERDA study was done by the Cadmus Group for
  single phase and three phase low voltage
  transformers.
• NYSERDA assumptions and their estimates of the
  installed efficiencies are used because NYSERDA
  savings are realistic.

10
Full Cost Analysis for Early Transformer
Replacement

• Full savings are the difference of annual losses
  between the NYSERDA baseline transformer and the
  higher efficiency transformer (level 2,3,4 or
  5/6).
• Assuming the cost of early replacement is the
  full cost of the higher efficiency transformer
  (level 2,3,4 or 5/6).
• Using the full cost of a higher efficient
  transformer results in non-cost effective
  measures for single phase transformers and cost
  effective measures for three phase transformers.

11
Incremental Cost Analysis for Transformer
Upgrades

• Incremental savings are the difference in losses
  between the TP-1 transformer and higher
  efficiency transformer level 2,3,4 or 5/6.
• Incremental cost is the difference between the
  TP-1 transformer cost and the cost of the higher
  efficiency transformer.
• Using the incremental cost of the higher
  efficiency transformer results in cost effective
  measures for single and three phase transformer.

12
Conclusion

• Higher-efficiency transformers level 2,3,4, or
  5/6 are not commercially available.
• We strongly recommend to the manufacturers to
  produce these higher-efficiency transformers in
  order that BPA can offer a transformer rebate
  program to the utility customers.