PROPOSED STANDARD PROTOCOL FOR
TRANSFORMER DE-ENERGIZING
Submitted to
REGIONAL TECHNICAL FORUM
Submitted by
CASCADE ENERGY
5257 NE MLK Jr. Blvd., STE 301
Portland, OR 97211
February 20, 2013
Standard Savings Estimation Protocol - Transformer De-Energizing
TABLE OF CONTENTS
1. PURPOSE............................................................................................................ 1
2. SUNSET DATE ...................................................................................................... 1
3. DEFINITION
OF KEY TERMS ..................................................................................... 1
4. ELIGIBLE PROJECTS ............................................................................................... 1
5. REQUIRED KNOWLEDGE AND SKILLS OF PRACTITIONER ................................................... 2
6. DELIVERY VERIFICATION ......................................................................................... 2
7. DATA COLLECTION REQUIREMENTS ........................................................................... 2
7.1. Transformer Characteristics............................................................................................... 2
7.2. No-Load Losses .................................................................................................................. 3
7.3. De-Energized Duration ....................................................................................................... 3
8. PROVISIONAL DATA REQUIREMENTS ......................................................................... 3
9. SAVINGS ESTIMATION STEPS ................................................................................... 3
9.1. Compute Savings for De-Energized Periods ...................................................................... 4
10. SAMPLING PROCEDURE ........................................................................................ 4
11. RELATIONSHIP TO OTHER PROTOCOLS AND GUIDELINES ............................................... 4
12. TYPICAL COST OF APPLYING THIS PROTOCOL ............................................................. 6
13. USER’S GUIDE TO THE SAVINGS CALCULATOR ............................................................ 6
APPENDIX A: NEMA TP-1 TRANSFORMER EFFICIENCY STANDARDS .................................... 8
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Standard Protocol – Transformer De-Energizing
1. PURPOSE
This protocol establishes a method by which annual electrical energy savings (kWh) can be estimated for
de-energizing an existing transformer when it is unloaded or when it is not in use. De-energizing a
transformer reduces energy use by eliminating the no-load losses of the energized transformer.
This protocol specifies minimum acceptable data collection requirements and the method by which
these data are to be used in computing savings. For some data elements, alternative sources of data,
considered to be of superior quality, are also defined and are allowed. Annual energy savings are
computed using the Microsoft Excel-based ‘Transformer De-Energizing Savings Calculator’ that
accompanies this document to ensure standardized application of the savings estimation methods.
2. SUNSET DATE
This protocol is approved for use until NEMA transformer efficiency standards change, or such time that
a protocol revision is proposed and adopted, but not longer than five years (February 20, 2017) from the
date it was approved by the Regional Technical Forum, whichever comes first.
3. DEFINITION OF KEY TERMS
Project. One instance of an individual transformer de-energizing and re-energizing as a result of
protocol implementation.
Baseline. This modifier, as in baseline transformer operation, refers to the unloaded, or no-load state of
an in-use transformer prior to de-energizing as a result of protocol implementation.
Delivery Verification. This is the process of verifying the state of the transformer, either energized or
de-energized.
No-Load Loss Power. The expended power of a transformer that is operating at its rated voltage and
frequency but is not supplying power to a load. No-load losses can include core loss, dielectric loss,
conduct loss in the winding due to excitation current, and conductor loss due to circulating current in
parallel windings.
Post. This modifier, as in post transformer de-energizing, refers to the period after the utility has
disconnected power from the transformer and it has been de-energized as a result of protocol
implementation.
4. ELIGIBLE PROJECTS
The following criteria define the eligible transformer de-energizing projects:
 Transformer type must be either liquid-filled or dry-type.
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Standard Savings Estimation Protocol – Transformer De-Energizing
 Transformer must be either single-phase transformer between 3 kVA – 167 kVA, or three-phase
transformer between 15 kVA – 1,000 kVA.
 Transformer must be classified as low voltage (less than or equal to 600V).
5. REQUIRED KNOWLEDGE AND SKILLS OF PRACTITIONER
The practitioner responsible for entering data into a savings calculator to develop project-specific
energy savings must possess the following:
 Understanding of the appropriate range of key variables and values required to accurately
input data
used to calculate transformer de-energizing energy savings.
The practitioner responsible for applying this protocol to a transformer must possess the following:
 A full understanding of appropriate safety procedures for working around transformers.
 Ability to identify, by visual inspection, the transformer type, rating, voltage, and phase.
6. DELIVERY VERIFICATION
The following delivery verification steps are taken by the program operator to ensure the protocol is
implemented as intended and is capable of achieving reliable energy savings:
 Verification that the transformer is de-energized on the date de-energizing is recorded by visual
inspection of utility records, and verification that the transformer is re-energized on the date reenergizing is recorded by visual inspection of utility records.
7. DATA COLLECTION REQUIREMENTS
The following data must be collected and entered into the Transformer De-Energizing Savings Calculator.
The minimum acceptable procedure for obtaining the data is specified.
7.1. Transformer Characteristics
 Transformer Type. Determined by visual inspection.
The transformer type is obtained from the
nameplate data on the transformer. A transformer may be one of the following types, which refers to
the method of cooling utilized: liquid-filled or dry-type. Alternately, if nameplate data is not available,
transformer type may be obtained from manufacturer’s published data sheets.
 Rated Capacity. Determined by visual inspection.
The rated capacity is obtained from the nameplate
data on the transformer. Alternately, if nameplate data is not available, capacity rating may be
obtained from manufacturer’s published data sheets.
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Standard Protocol – Transformer De-Energizing
 Voltage and Phase. Determined by visual inspection.
The voltage and phase of the transformer are
obtained from the nameplate data on the transformer. Alternately, if nameplate data is not available,
voltage and phase may be obtained from manufacturer’s published data sheets.
7.2. No-Load Losses
 Determination of No-Load Losses. Transformer no-load losses shall be obtained through the NEMA
TP 1-2002 transformer efficiency standards shown in Appendix A of this protocol. Alternately, if a
manufacturer no-load loss for the specific transformer exists, or a real power measurement of the
transformer no-load loss was taken subsequent to installation of the transformer, then either can be
used to estimate the no-load loss of the transformer in lieu of using the NEMA default tables.

Default No-Load Loss. The default no-load loss shall be based on NEMA TP 1-2002 transformer
efficiency standards (see Appendix A), and are calculated in the Transformer De-Energizing
Savings Calculator using the method described in Section 9.1.

Alternate Method Using Manufacturer No-Load Loss. The no-load loss may be determined
through manufacturer-listed specifications in lieu of using the default tables. The no-load loss
may be available on the transformer nameplate, published specifications, operations and
maintenance manual, or by contacting the manufacturer directly.

Alternate Method Using Real Power Measurement. If a real power measurement of the
transformer no-load loss has been taken subsequent to installation of the transformer, this may
be used in lieu of the default tables. The real power measurement should follow industryaccepted procedures and/or be in accordance with IEC60076 or IEEE/ANSI C57.
7.3. De-Energized Duration
 De-Energized Duration. Determine the number of hours per year the transformer is de-energized
based on visual inspection of utility record date(s) of de-energization and date(s) of re-energization.
8. PROVISIONAL DATA REQUIREMENTS
There are no provisional data collection requirements.
9. SAVINGS ESTIMATION STEPS
Savings are estimated using the Transformer De-Energizing Savings Calculator that accompanies this
protocol. Savings are estimated as follows.
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Standard Savings Estimation Protocol – Transformer De-Energizing
9.1. Compute Savings for De-Energized Periods
 No-Load Loss Power. Determine the no-load loss power in watts using the NEMA TP 1-2002 default
efficiency tables, or one of the alternate methods listed in Section 7.2 and the following equation:
100 − %
𝑆𝐵 × 𝑃 × 1,000 × ( % )
𝑁𝐿 =
2
𝑃
1 + (𝑃
)
𝑚𝑎𝑥%
Eq. (1)
Where,
𝑁𝐿
𝑆𝐵
𝑃
=
=
=
%
=
𝑃𝑚𝑎𝑥%
=
No-load loss, watts.
Nameplate rating, kVA.
Per unit load relative to nameplate rating at which the efficiency is
specified. P is defined as 0.50 for liquid-filled transformers, and 0.35 for
dry-type transformers.
Transformer efficiency, which is assumed to be the NEMA TP-1 2002
minimum transformer efficiency standard.
The load point at which maximum efficiency occurs.
For this analysis, it is assumed that 𝑃 = 𝑃𝑚𝑎𝑥% . Thus, the equation can be resolved to:
100 − %
𝑆𝐵 × 𝑃 × 1,000 × (
)
%
𝑁𝐿 =
2
Eq. (2)
 Annual De-Energized Hours. Determine the number of de-energized hours for the transformer on an
annual basis through visual inspection of utility records noting de-energization date and planned reenergization date.
 Annual Savings.
Divide the no-load loss power in watts by 1,000 W/kW, and multiply by 24 hrs/day
times the number of de-energized days per year. This results in the annual energy savings estimate in
kWh.
𝐸𝑆𝑎𝑣𝑒𝑑 = 𝑁𝐿 × DeEnergized Days ×
24
1,000
Eq. (3)
10. SAMPLING PROCEDURE
No sampling is permitted by this protocol. Data collection and savings estimation is required for each deenergized transformer.
11. RELATIONSHIP TO OTHER PROTOCOLS AND GUIDELINES
The relationship between this protocol and other relevant protocols and guidelines is as follows:
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Standard Protocol – Transformer De-Energizing
 NEMA TP 1-2002, Guide for Determining Energy Efficiency for Distribution Transformers. This guide
establishes the minimum efficiency ratings for transformer manufacturers. These efficiencies were
adopted by EPACT in 2005, and are referenced in EPACT 135(c)(4), and the Code of Federal
Regulations CFR 413 Subpart (k), and apply to all transformers manufactured after January 1, 2007.
 IEC60076 and IEEE/ANSI C57. These standards reference the technical requirements, including the
design, testing and application of single and three-phase power transformers. They are referenced
here for the purposes of taking accurate power measurements of transformers at no-load conditions.
 International Performance Measurement & Verification Protocol (IPMVP), Volume I, 2007
(www.ipmvp.org). This protocol is consistent with Option A - Retrofit Isolation: Key Parameter
Measurement described in the IPMVP, as a number of key parameters are entered or indirectly
assumed.
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Standard Savings Estimation Protocol – Transformer De-Energizing
12. TYPICAL COST OF APPLYING THIS PROTOCOL
Shown below is an estimate of typical cost of applying this protocol to a single transformer.
Item
Hours $ / Hour
Total Cost
Labor
Practitioner
Data gathering
Savings estimate
Total
2
$110
$ 220
0.5
$110
$ 55
$275
13. USER’S GUIDE TO THE SAVINGS CALCULATOR
The Transformer De-Energizing Savings Calculator calculates the annual energy savings following the
steps outlined in Section 9 of this protocol.
Step 1: Manufacturer No-Load Loss Rating Available. The default selection is “N” for No. However if
an alternate method is used to obtain the no-load loss rating as described in Section 7.2, select “Y”
for Yes.
Step 2: Transformer Rated Capacity. Enter the rated capacity in kVA into the Savings Calculator. The
transformer rating (size) must be between 3 – 167 kVA for single-phase transformers, and 15 – 1,000
kVA for three-phase transformers, as described in Section 4. If a transformer size is outside the
eligible size range, then the calculated Annual Energy Savings will return “ERROR!’’.
Tables 1 and 2 in Appendix A show typical transformer ratings, which are the default sizes used in the
Savings Calculator to calculate no-load losses. If a non-standard transformer size is input into the
calculator, the Savings Calculator will calculate the no-load loss based on the next smaller listed
transformer size.
Step 3: Transformer Phase. Select “1” for single-phase transformers, or “3” for three-phase
transformers from the drop-down list.
Step 4: Transformer Type. Select “Liquid” for liquid-filled transformers, or “Dry” for dry-type
transformers from the drop-down list.
Step 5: No-Load Loss. If “Y” was selected in Step 1, enter the manufacturer listed no-load loss in watts.
If “N” was selected in Step 1, the default no-load loss will automatically be displayed in watts, based
on the inputs from the previous steps and the NEMA TP-1 efficiency standards showing in Tables 1
and 2 in Appendix A.
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Standard Protocol – Transformer De-Energizing
Step 6: Number of Days per Year Transformer is De-Energized. Enter the number of days in previous
year that the transformer was de-energized. If a number greater than 365 is entered, then the
calculated Annual Energy Savings will return “ERROR!”.
Step 7: Annual Energy Savings. The Annual Energy Savings in kWh/yr is calculated based on the inputs
from the previous six steps. If the Annual Energy Savings displays “ERROR!”, check the inputs in Steps
2 and 6 to ensure they are within the eligible criteria.
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Standard Savings Estimation Protocol – Transformer De-Energizing
APPENDIX A: NEMA TP-1 TRANSFORMER EFFICIENCY
STANDARDS
The following tables are the NEMA TP-1 2002 minimum efficiencies and estimated no-load losses based
on the calculation described in Section 9.1.
Table 1: NEMA TP-1 Minimum Efficiency and Transformer
Design Losses for Liquid-Filled Low-Voltage Transformers
Single Phase
Size
(kVA)
3
5
7.5
10
15
25
37.5
50
75
100
167
No-Load
Efficiency Loss
(%)
(W)
98.0%*
15
98.2%*
23
98.3%*
32
98.3%
43
98.5%
57
98.7%
82
98.8%
114
98.9%
139
99.0%
189
99.0%
253
99.1%
379
Three-phase
Size
(kVA)
15
30
45
75
112.5
150
225
300
500
750
1,000
No-Load
Efficiency
Loss
(%)
(W)
98.0%
77
98.3%
130
98.5%
171
98.7%
247
98.8%
342
98.9%
417
99.0%
568
99.0%
758
99.1%
1,135
99.2%
1,512
99.2%
2,016
Table 2: NEMA TP-1 Minimum Efficiency and Transformer
Design Losses for Dry-Type Low-Voltage Transformers
Single Phase
Three-phase
No-Load
No-Load
Size
Efficiency Loss
Size
Efficiency
Loss
(kVA)
(%)
(W)
(kVA)
(%)
(W)
3
97.1%*
16
15
97.0%
81
5
97.3%*
24
30
97.5%
135
7.5
97.5%*
34
45
97.7%
185
10
97.6%*
43
75
98.0%
268
15
97.7%
62
112.5
98.2%
361
25
98.0%
89
150
98.3%
454
37.5
98.2%
120
225
98.5%
600
50
98.3%
151
300
98.6%
745
75
98.5%
200
500
98.7%
1,152
100
98.6%
248
750
98.8%
1,594
167
98.7%
385
1,000
98.9%
1,946
*Efficiencies are not provided by NEMA for these transformer sizes. Tabulated efficiencies are extrapolated
estimates.
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