2. 2 /
GE /
June 7, 2004
Optimizing TP-1 Transformers…
Merritt & Chaitkin, Pulp/Paper Conf 2004
• Minimum PU Loss when LL = NLL
• PU Load at Min PU Loss
~ 1 / Square root of “Loss Factor” (LL / NLL)
• Designing for Min Losses at higher loading may not
be cost effective
• Work with MV transformer vendor by specifying
Present Value of NLL $/W and LL $/W (“A” and “B”)
to get optimized design.
3. 3 /
GE /
June 7, 2004
Applying High Efficiency Transformers
Haggerty, Malone, Crouse; IAS Magazine, Nov/Dec 1998
• Life-cycle or total owning cost
• Examples of how Loss Evaluation$/W can affect
cost effectiveness of a design
• Liquid types have lower losses than VPI dry types
• Cast coil can have losses comparable to liquid type
• Higher efficiencies have higher manufacturing costs
• Use Internal Rate of Return (IRR) method for
evaluation
• Loading should be considered
• Not “Is it Justified?” But “How much should we invest?”
4. 4 /
GE /
June 7, 2004
Transformer Economic Evaluation
Rasmussen, IAS Transactions March/April 1984
• Demand charges
• Transformer peak load does not necessarily
coincide with service peak load.
• Energy charges
• Utility rate increases
• Depreciation/Tax effects - Modified Accelerated
Cost Recovery System (MACRS), 15 years
• Cash Flow/ Present Value – Compare alternatives
• Rate of Return “ROR” (IRR) – Profitability indicator
5. 5 /
GE /
June 7, 2004
Preceding available from
ieeexplore.ieee.org
• Nominal charge to non-members
• IAS Members can download for FREE
• 2009 IAS membership adder: $20
• Access to IEEE IAS papers dating back
> 30 years!!
6. 6 /
GE /
June 7, 2004
NEMA TP1-2002
Guide for Determining Energy Efficiency for Dist Transformers
• A (NLL) & B (LL) factor evaluation equations
• Download for free from www.nema.org
7. 7 /
GE /
June 7, 2004
US Department of Energy
Appliances and Commercial Equipment Standards –
Distribution Transformers
• Federal Register Oct 12, 2007
• 10 CFR Part 431 Final Rule
• MV Transformer minimum efficiency
• Liquid AND dry-types
• Effective 2010
• NOT same as NEMA TP-1……Higher!
8. 8 /
GE /
June 7, 2004
Utility Rate Information – PG&E
http://www.pge.com/tariffs/rateinfo.shtml
Annualized
Average
PG&E
Schedule
Max Demand
Max
Demand
Amps @
480V
Peak
Part-
Peak
Off-
Peak
Part-
Peak
Off-
Peak
A1 < 200kW 301 $0.20 $0.20 $0.20 $0.14 $0.14 $0.17
A6 200kW < < 499kW 750 $0.41 $0.19 $0.12 $0.14 $0.12 $0.17
A-10 < 499kW 750 $0.14 $0.14 $0.14 $0.11 $0.11 $0.12
E-19 499kW < < 1000kW 1504 $0.16 $0.11 $0.09 $0.09 $0.08 $0.10
E-20 > 1000kW $0.15 $0.10 $0.08 $0.09 $0.08 $0.09
Summer: May through Oct
Winter: Nov. through April
Peak: 12:00 Noon - 6:00PM
Part-Peak: 8:30AM to 9:30PM
Off-Peak: 9:30PM to 8:30AM
SECONDARY VOLTAGE ENERGY RATES
EXCLUSIVE OF DEMAND CHARGES, IF
APPLICABLE Summer Winter
9. 9 /
GE /
June 7, 2004
A Simple NPV Calculation
Comparing energy cost
Power Savings (watts) 1 1 1
Hours in a year 8760 8760 8760
Annual Energy Savings (kWh) 8.76 8.76 8.76
Energy Inflation Factor 3.00% 3.00% 3.00%
Energy cost ($ /kWh) $0.10 $0.15 $0.20
NPV Discount Rate 5.00% 5.00% 5.00%
15 Year NPV $10.45 $15.68 $20.91
