s

A

-znclosure (1)

su Paper for the Distribution Transformers Test Procedures Workshop

February 10, 199

The Department is interested in receiving information and statements to help resolve the

following issues:

a. Adoption of national and international consensus standards in the test

procedures for determining ene rgy efficiency of distribution transformers.

The Department is considering incorporating by reference six standards as the test

procedures. The two primary test standards have been approved by the American National

Standards fintitute (ANSI) and prepared by the Institute of Electrical and Electronics Engineers

(IEEE): ANSI C57.12.90-1993, "IEEE Standards Test Code for Liquid-Immersed Distribution,

Power and Regulating Transformers and IEEE Guide for Short Circuit Testing of Distribution

and Power Transformers," and ANSI C57.12.91-1995, "IEEE Standard Test Code for Dry-Type

Distribution and Power Transformers." Two other standards, ANSI C57.12.00-1993, "IEEE

Standard General requirements for Liquid -Immersed Distribution, Power and Regulating

Transformers," and ANSI C57.12.01-1989, "IEEE Standard General Requirements for Dry-Type

Distribution and Power transformers, Including Those with Solid Cast and/or ResinEncapsulated Windings," specify reference temperatures and joss tolerances for the transformers

being tested and recommend preferred continuous power ratings for transformers. C57.12.00

also specifies accuracy tolerances of the measuring systems.

The Department is also considering incorporating by reference .a guide prepared by the

, ( 

·)!.;nelosure (1) 

b,ua Paper for the Distribution Tnmlformers Tat Procedures Workshop 

011 February 10, 1991 

The Department is interested in receiving information and statements to help resolve the 

following issues: 

. a. Adoptioll of national and international consensus standards in the tat 

procedures for detemlJinin~ energy efficiency of distribution transformers. 

The Department is co;'lsidering incoIpOrating by reference six standards as the test 

procedures .. The two primary test ~dards have been approved by the American National 

Standards Institute (ANSI) and prepared by the Institute of Electrical and Electronics Engineers 

(IEEE): ANSI CS7:12.90-1993, "IEEE Standards Test Code for Liquid-Immersed Distribution, 

Power and Regulating T~ormers and IEEE Guide, for Short Circuit Testing of Distribution 

and Power Transformers." and ANSI CS1.12.91-199S. "IEEE Standard Test Code for Dry-Type 

Distribution and Power Transformers." Two other standards, ANSI CS7.12.OO-1993, "IEEE 

Standard General requirement~ for Liquid -Immersed Distribution, Power and Regulating 

Transformers." and ANSI CS7.12.01-1989, "IEEE Standard General Requirements for Dry-Type 

Distribution and Power tfansformers, Including Those with Solid Cast andlor ResinEncapsulated Wmdings," specify reference temperatures and Joss tolerances for the transformers 

being tested and recommend preferred continuous power ratings for tran,sformers. CS7.12.oo 

also specifies accuracy toieranees of the measuring systems. 

The Department is also ~~id~ring incorporating by reference.a guide ~repared by the 
National Electrical Manufacturers Association (NEMA), 1-1996, "Guide for Determining

Efficiency for Distribution Transformers," with respect to reference temperatures and

measures ofenergy tion. Finally, the Department is considering incorporating by

refererice a single clause, 4.11.1, in a standard prepared by the International Standards

Organization (ISO), ISO Standard 9001-1993, "Quality Systems - Model for quality assurance in

design, development, production, installation, and icing," regarding quality assurance of the

test and measuring equipment.

All of the above-m tion(®d stagy. dards contain more information than that applicable to loss

or efficiency testing. Hence, the Department only intends to incorporate by reference the

applicable clauses in the proposed test procedures . Such requirements as reference temperatures,

measures ofenergy consumption, measurement accuracy requirements are not fully consistent

among the cited standards. DOE intends to use uniform test requirements in the proposed test

procedures for both the liquid-immersed and dry-type transformers. Certain items, such as the

sampling plan and the concept of a basic model , are not addressed by the referenced standards but

are required in the DOE test procedures.

The Department is aware of an effort by NEMA to produce a standard (TP 2, a

companion to TP 1) on test procedures for efficiency determination of distribution transformers.

DOE will examine this document for possible incorporation by reference in the proposed DOE

test procedures, once the standard has been approved and finalized.

Questions and Request for Comments

(1) Are the six consensus standards appropriate for referencing as the DOE-required test

practice?

4 

- . National Electrical Manufacturers Association (NEMA). TP 1-1996,. "Guide for Determining 

Energy Effi~ency for Distribution Transformers," with respect to reference temperatures and 

measures of energy cOnsumption. Finally, the Department is considering incorporating by 

reference a single clause, 4.11.1,_ in a standard prepared by the International Standards 

Organization (ISO), ISO Standard 9001-1993, "Quality Systems - Model for quality assurance in 

design, development. production, installation, and servicing," regar~ing .quality assUrance of the 

test and measuring equipment. 

All of the above-mentionl%l stru.dards contain more information than that applicable to loss 

or efficiency testing. Hen~, the Departl.nent only intends to incorporate by reference the 

applicable clauses in the proposed test pl'l.lcedures. Such requirements as reference temperatures, 

measures of energy consumption, m~surement accuracy requirements are not fully consistent 

among the cited standards. DOE intends to use uniform test requirements in the proposed test 

procedures for both the liquid-immersed and dry-type transformers. Certain items, such as the 

sampling plan and the concept of a basic mode~ are not addressed by the referenced standards but 

are required in the DOE test procedures. 

The Department is aware of an effort by NEMA to produce a standard (TP 2, a 

. companion to TP 1) on test procedures for efficiency determination of distnDution transformers. 

DOE will examine this document for possible incorporation by reference in the proposed DOE 

test procedures, once the standard has been approved and finalized. 

Questions and Regpest for Comments 

(I) Are the six consensus standards appropriate for referencing as the DOE-required test 

pra~ce'l 
(2) Is the clause-by-clause referencing of ANSI standards in draft 5 of "Test Procedure for

on Transformers,' pp. 16.20, too detailed? Should such referencing

escribing dc resistance, no-l loss, and to loss measurements-and by alluding to the

abbreviated by referencing only the appropriate sections in the two test codei-those

c clauses where qxceptions are made?

(3) Should additional relevant ds now in preparation and approval stages, such as

IEEE PC57.123/D1.1 "Draft Guide for Transformer Loss Measurement" and

NEMA -2 considered as additional or alternative references? Will such standards

add to the knowledge base of the already existing consensus standards and

enhance the user convenience?

b. Burden imposed on industry, especially small manufacturers, by additional

testing and data processing

During the information gathering, and preparation of the draft, several items have caused

concern and prompted debate during visits and presentations to interested parties. There was a

general concern about additional and excessive burdens imposed on manufacturers as a result of

new regulations, standards and testing requirements. Small manufacturers with limited test

facilities were apprehensive about E's test requirements.

The Department strives to base the proposed test procedures as much as possible on the

existing standards. The actual tests and measurements in the NISI' draft test procedures are the

'The National Institute of Standards and Technology has developed a set of draft test

procedures for distribution transformers which DOE is distributing to stakeholders in preparation

for the public workshop.

(2) Is the clause-by-clause referencln~ of ANSI standards in draft 5 of "Test Procedure for 

Distri~on Transformers;" PI'. 16 - 20, too detailed? Should mch referencing be 

abbreviated by referencing only the appropriate sections in the two test code&-those 

describing dc resistance, n~IQad loss, and lpad loss measurements-and by alluding to the 

specific clauses where ~ceptions are made? 

. (3) Should additional relevant standards now in preparation and approval stages, such as 

IEEE peS7 . 1231D 1.1 "Draft Guide for Trannormer Loss Measurement" and 

NEMA TP-2 be considered as additional or alternative references? Will such standards 

add to the knowledge base of the already existing consensus standards and 

enhance the user convenience? 

b. Burden imposed on industry, especiaUy smaD manufadurers, by additional 

testing and data processing 

During the infc;>nnation gathering and preparation of the draft, several items have caus~ 

concern and prompted debate during visits and presentations to interested parties. There was a 

general concern about additional and excessive burdens imposed on manufacturers as a result of 

new regulations, standards and testing requirements. Small manufacturers with limited test 

facilities were apprehensive about DOE's test requirements. 

The Department strives to base the proposed test procedures as much as possible on the . . 

existing standards. The actual tests and measurements ~ the NIST1 draft test procedures are the 

. lThe National Institute of Standards and Technology has developed a set of draft test 

.' procedures for distnDution transfomiers whic:h DOE is distributing to stakeholders in preparation 

for the public workshop. . 
same as in the existing p ce. Ile draft test procedures include new requirements for sampling

and data Processing involving adjustment to now reference temperatures and calculation of

efficiency from the loss data.

DOE would ' e comments from manufacturer s about eir specific situations and

anticipated difficulties, and suggestions to how problems can be solved and burdens minimized.

Qusafians and It oast for Comments

(1) What specific requirements in the NIST draft test pr sire are causing concern about

significant additional burden imposed by testing requrements? Please cite difficulties

anticipated.

c. Definition of "basic model" for distribution transformers.

It is common for a single transformer manufacturer to make numerous models of

transformers covered by EPCA. Often, several models are essentially the same transformer but

with each model having some refinement that does not affect energy efficiency or ormance. A

manufacturer may determine which models have electrical and mechanical characteristics that are

essentially identical. Each such group of models may be categorized into a family , and only

representative samples within each family, or "basic model", would be tested.

With regard to the residential appliance programs, 10 CFR 430.2, the term "basic model"

is defined as follows: "Basic model means all units of a given type of covered product (or class

thereof) manufactured by one manufacturer and [with respect to dishwashers, for example] which

do not have any differing physical and functional characteristics that affect energy consumption."

DOE is considering a similar definition for transformers: "Basic model means all units of a

• A 

'lame as in the exiSting practice~ The draft test procedures include new requirements for sampling 

ad data processing involvirig adjustment to new reference temperatures and calculation of 

efficiency from the loss data . 

. DOE would like comments from manufacturers about their specific situations and 

anticipated .difficulties, an~ suggeStions as to how problems can be solved and burdens minimized. 

"Questions and Request for Comments 

(l) What specific requirements in the NIST draft test pr:>eedut'e are causing concern about 

significant additional burden imposed by testing requir"ments? Please cite difficulties 

anticipated. 

c. Definition of "basie model" for distribution transformers. 

It is common for a single transformer manufacturer to make numerous models of 

transformers coveted by EPCA Often, several models are essentially the same transformer but 

. with each model having some refinement that does not affect energy efficiency or performance. A 

manufacturet may determine which models have electrical and mechanical characteristics that are 

essentially id,entical. Each such group of models may be categorized into a family, and only 

representative samples within each family, or "basic model", would be tested. 

With regard to the residential appliance programs, 10 CPR. 430.2, the term "basic model" 

·is defined as ,fonows: "Basic mOdel means all units of a given type of covered product (or class 

" . ' 

thereof) manufactured by on~ manufacturer and [with respect to dishwashers. for example] which 

do not have any differing physical and functional characteristics that affect energy consumption." 

DOE is considering a similar definition for transform~s: "Basic model means all units of a 
®® Blven type of covered equipment (or class thereof) manufactured by, a single ' er and,

ith raped to. distribution which have the same ratim have electrical

eristics that are essentially identical, and do not have any differing physical or electrical

'stirs which affect 4 ion or efficiency." For the purpose of this definition,

68rating" would mean standard output power rating, such as one of those tabulated in NEMA TP

1, tables 4- 1 and 4®2.

Questions and Request for Comments

(1) In view of such a definition for a "basic model," do you anticipate significant difficulties in

grouping your products into basic models?

(2) For those manufacturers having only a few items per model, would it be possible to

combine a number of models into families of basic models, e.g.,,grouping many actual

production models of the same nominal kVA rating in one family of models?

d. Sampling plan for units, to be test ed.

The Code ofFederal Regulations (CFR), in 10 CFR Part 430 §430.23 outlines

sampling plans for compliance testing. For example, under §430.23.(q)(1), "For each basic model

of fluorescent lamp ballasts, as defined in paragraph (14) of §430.2, a sample of sufficient size, no

less than four, shall be tested to insure that ... (ii) Any represented value of the ballast efficiency

,factor or other measure of energy consumption of a basic model for which consumers would

favor a higher value sno greater than the lower of(A) the mean of the sample or (B) the

lower 99 percent confidence limit of the true mean divided by 0.99."

• 4 given type of covered ~pment (or class thereof) manufactured by a single manufacturer and) 

. ·wi~ respect to. distribution transformers, which have the same rating, have eleCtrical 

·dw'aderistics that are essentially identical, and do not have any differing physical or electrical 

characieristics which affect energy consUmption or efficiency." For the purpose of this definition, 

"rating" would mean standard· output power rating, such as one of those tabulated, in NEMA TP 

1, tables 4 - 1 and 4 - 2. 

Questions and ReQuest. for Comments 

(1) In view of such a definition for a "basic mode~ tI do you anticipat~ significant difficulties in 

grouping your products into basic models? 

(2) For those manufacturers having only a few items per model, would it be possible to 

combine a number of models into families of basic models, e.g., grouping many actual 

production models of the same nominal kVA rating in one family of models? 

d. Sa~piing plan for units.to be tested. 

The Code of Federal Regulations (CFR). in 10 CFR Part 430 §430.23 outlines. 

sampling plans for compliance testing. For ~ample. under §43().23.(q)(1). "For each basic model , oftluorescent lamp ballasts. as defined in paragraph (14) of §430.2. a sample of sufficient size, no 

. less than four. shall be tested to insure ihat ... (li) Any represented value of the ballast efficiency 

~or or other measure of energy consumption of a basic model for which consumers would 

&vor a higher value shall be no greater than the lower of (A) the mean of the sample or (B) the 

. lower 99 percent confidence limit of the true mean, divided by 0.99." . . 
The sampling for enforcement testing is provided in 10 CFR P 430 §430.70,

ip ' plan is

f a determination of co

applicable standard.

of distribution transformers:

on the statistical t-test yielding 97.5 percent probability

liance when the true mean efficiency is equal to the

this time the Department is considering one of two sampling plans for compliance

1) TIM plan in §430.23, using the lower 95 percent confidence limit, but without

specifying the minimum number ofunits in the sample (A minimum of two units is implicitly

required to estimate the confidence limit.) The "IC" factor, based on the six percent lots

tolerance specified in ANSI C57. 12.00 and C57. 12.01, is selected to be 0.999.

2) A modified version of the proposed sampling plan for enforcement testing of motors as

outlined in 61 60474 - 60475, Appendix B to Subpart 'G.of Part 431, "Sampling Plan for

Enforcement Testing," is considered for compliance testing of distribution transformers. The

considered modification consists of replacing the factor (120 - 0.2 SFE)/SFE(20 - 0.2 SFE) in

equation (5) by the new factor (106 - 0.06 SFE)/SFE(6 - 0.06 SFE). This plan yields a 90 percent

probability of obtaining a determination of compliance when the true mean is equal to the

standard.

For the enforcement testing of tformers the Department is considering a plan similar

to 2) above but changing the probability of det ermination of the compliance from the 10th

-percentile to the 2. 5th percentile.

Questions and Request for Comments

(1) Please provide comments on the two sampling plans DOE is considering for compliance

.. . 

• "'.1' •• 

. The san;tpling plan for enforcement testing is provided in 10 CFR Part 430 §430.70, 

'Appendix B. This. sampling plan is baSed on the statistical t-test yielding 97.5 ~cent probability 

of obtaining a determination of compliance when the trUe mean efficiency is equal to the 

. appliCable standard. 

. Ai this time the Department is considering one of two sampling plans for compliance 

t~ of distribution transformers: 

1) The plan described in 1430.23. using the lower 95 percent confidence limit. but without 

specifying the minimum number of units in the sample (A minimum of two units is implicitly 

required to estimate the confidence limit.) The "K" factor, bued on the six percent lOGS 

tolerance specified in ANSI C57.12.00 and C57.12.01. is selected to be 0.999 . 

. 2) A modified version of the proposed sampling plan for enforcement testing ofmotars as 

outlined in 61 F.R 60474 - 60475, Appendix B to Subpart G.ofPart 431, "Sampling Plan for 

. , . 

Enforcement Testing," is considered for compliance testing of distnbution transformers. The 

. considered modification consists ofreptaeing the factor (120 ~ 0.2 SFE)/SFE(20 - 0.2 SFE) in 

equation (5) by the new factor (106 - 0.06 SFE)lSFE(6 - 0.06 SFE). This plan yields a 90 percent . . 

. probability of obtaining a determination of compliance when the true mean is equal to the 

standard. 

For the enforcement testing of transformers the Department is considering a plan similar 

to 2) above but changing the probability ofdeiermination of the compliance from the 10th 

.percentile to the 2.Sth percentile. 

Questions and Request for Comments 

(1) Please provide comments on the two sampling plans DOE is considering for compliance . ' . 
(2) Please describe other approaches you believe DOE should consider.

Selection of a measure of energy consumption for distribution transformers.

DOE considers efficiency as the preferable measure of energy consumption. The industry

ce, as required by the cited ANSI standards, has been to mandreport transformer

losses. DOE believes that for energy conservation purposes =111 ciency is a better measure as it

presents a unified and normalized measure allowing manufacturing trade-offs between the two

types oflosses. -(Transformer losses would still be measured to determine efficiency.) The

Department would like to obtain comments on this measure of energy consumption and the

practicality of its use for the DOE test procedures.

Questions and BQ]jj9 for Comments

(1) Are there any strong reasons why efficiency should not be used?

(2) Should other measures of energy consumption be considered : e.g., loss, power normalized

relative to output kVA, either on per unit basis or percentage basis?

(3), Is reporting ofefficiency and losses at reduced loading levels appropriate for an energy

conservation standard?

10

. fSelection of reference temperatures the reference temperatur es in consensus

standards lack uniformity.

testing. 

(2) Please descrlDe other approaches you believe DOE should consider. 

eo Selection of" measure of eneray consumption for distribution transformers. 

DOE co~ders' efficiency as the preferable measure of energy consumption. The industry 

practice, as required by the cited ANSI standards, bas been to m~e and ~eport transformer 

losses. DOE believes that for energy conservation purposes efficiency is a better measure as it 

presents a unified and normalized measure allowing· manufacturing trade-offs between the two 

types of losses. '(Transformerlosses would still be measured to determine efficiency.) The 

Department would like to' obtain comments on this measure of energy consumption and the 

practicality of its use for the DOE test procedures. 

Questions and Request for Comments 

(1) Are there any strong reasons why efficiency should not be used? 

(2) Should other measures of energy consumption be considered: e.g., loss. power normalized 

relative to output kV A, either on per unit basis or percentage basis? 

(3). Is reporting of efficiency and losses. at .reduced loading levels appropriate for an energy 

conservation standard? 

f. Selection of reference temperatures - the reference temper~tures in consensus 

standar~s lack uniformity. 
C57.12.00 specifies reference temperatures for liquid immersed o : 20°C for

no-load losses 85°C for load lo on 20°C dent temperature and 65 °C

temperature rise at the rated full load. 057. 12.01 s es five, reference temperatures for load

losses load: 80, , 135, 150, and 170°C based on 20°C ambient temperature

and temperature rises of five insulation classes; no reference temperature is specified for no-load

losses. I specifies reference temperatures of 20°C for no-load losses of both types of

tranArmers, 85 °C for load losses of liquid- immersed transformers, and 75 °C for load-losses of

all dry-type transformers. 1 specifies efficiency at less than the rated full load-S0 % of the

rated load for all liquid- immersed and medium voltage dry-type transformers, 35%

of the rated load for the low voltage dry-type transformers. NIST calculated the temperature

rises for reduced loading per TP 1. After examination, these data suggest that 75 °C represents an

approximate average of the ten conditions involving two loading levels and five temperature rises.

A similar calculation was ormed for the liquid-immersed transformers, yielding a temperature

rise of 35 °C and consequently a "new reference temperature" of 55°C.

DOE is considering using 20°C as the reference temperature for no-load losses of all

transformers, 75°C for load losses of dry type transformers, and 55°C for load losses of liquidimmersed transformers, should the future DOE energy conservation standard require loading

levels as in 1 . DOE 'eves these reference temperatures would make representations of test

data for both types of transformers more consistent.

estions and Request for Com is

Please provide comments, especially if there are in your view strong reasons for or against

the following modifications in reference temperatures from the values established in ANSI

'0 .' , CS7.12.00 specifies reference temperatUres for liquid immersed transformers: 200

e for 

no-load losses and 8S·C fur load losses, based on 200 e ambient'temperature and 6Soe 

. . 

temperature riSe at the rated fiillload. CS7.12.01 specjfies five, r~ference temperatures for load - ' ' I 

losses at the rated full load: 80, 100, 13S, lS0, and 1700 e based on loDe ambient temperature 

and tempera~e rises of five insulation classes; no rd'erence temperature is specified for no-load 

losses. TP 1 specifies reference temperatures of20°C for no-lOad lQsses of both types of 

transformers, 8SoC for load losses of liquid-immersed transformers, and 'SoC for load-losses of 

an dry-type transformers. TP 1 specifies efficiency at less than the rated full load-SO % of the 

, 

rated load for all liquid-immersed transformers and medium voltage dry-type transformers, 3S% 

of the rated load for the low voltage dry-type 'transformers. NIST calculated the temperature 

rises for reduced loading per TP 1. After examination, these data suggest that 7SoC represents an 

approximate average of the ten conditions involving two loading levels and five temperature rises. 

A similar calculation was performed for the liquid-immersed transformers, yielding a temperature 

rise of3SoC and conseque~tly a "new reference temperature" ofSSoC. 

DOE is considering using lOoe as the reference temperature for no-loa~ losses of all 

transformers, 1SoC for load losses of dry-type transform~rs. and SSoC for load losses of liquid-

~ersed transformers. should the future DOE energy conservation standard require loading 

, , 

levels as in TP 1. DOE believes these reference teniperatures would make representations of test 

data for both types of transformers more consistent. 

Ouestions and ~eguest for Comments 

Please provide comments.especiallyif~ere are in your view strong reasons for ()r against 

the following modifications in ref~ence temperatUres from the values established in ANSI 
Standards C57.12.00 and C57.12.01:

(1) reference temperature of 20°C for no-load losses of dry-type transformers (also

by TP 1).

(2) Specifying a single reference temperature of 75°C for load losses of dry-type transformers

having all five insulation ses. two loading levels (also required by 1), in effect

10 temperature rise conditions are approximated by one. Calculation of the actual

temperature rises indi tes that for four conditions the reference temperature rise is

underestimated (the actual temperature will be higher than 75 °C), for five it is

overestimated, and for one the calculated temperature is 75°C.

(3). Specifiling a reference temperature of 55°C for load losses of liquid-immersed

transformers at 50% load.

g. Requirement for applying corrections to measurement data of both liquidimmersed and dry-type types of tsformers.

C57.12.90 requires corrections for the phase angle error of m easuring instruments when

measuring load losses having a low power factor. An algorithm is provided in C57.12.90 to

calculate this correction and a table summarizing conditions under which this correction should be

applied or can be neglected. This standard also specifies corrections for the no-load loss data if

measurements are performed otherthan the specified reference temperature of 200C. Again,

an algorithm is provided. Such corrections are not required in C57. 12.91 for dry-type

I T

o· 

Standards CS7:12.00~ CS7.12.oi: 

I (l) Speclfying reference temperature of 20°C for no-load losses of dry-type transformers (also 

required by TP 1). 

(2) SpecifYing a single reference temperature of7SoC for load l~sses of dry-type transformers 

baving all five insulation clusesand two loading levels (aI~ required by TP 1), in effect 

10 temperature rise conditions are approximated by one. Calculation of the actual 

temperature rises mdicates ~t for four conditions the reference temperature rise is 

underestimated (the actual temperature will be higher than 7S0C), for five it is 

overestimated, and for one the calculated temperature is 7SoC. 

(3) Specifying a reference temperature ofSSoC for load losses of liquid-immersed 

transformers at SOOIO load. 

I. Requirement for applying corrections to measurement data of both liquidimmersed and dry-type types of transformers •. 

C57 .12.90 requires corrections fo~ the phase an~e error of measuring instruments when 

· measuring load losses having a low' power factor. An algontbm is provided in CS7.l2.90 to 

Calculate this correction and a table summarizing Conditions under which this correction should be 

applied or can be neglected. This standard also specifies corrections (or the no-load loss data if 

measurements are performed at other than the specified reference temperature of 20°C. Again, 

an algorithm is provided. Such corrections are not tequired in CS7.12.91 for dry-type . 
brmen DOE is considering applying corrections to both

estions It uest for r o

.. . corrections, if required, to memrement data ofdry.

is already done for liquid immersed transformers?

Requirement for quality assumnce in testing.

C57.12.00 provides a table of u.ncertainty'limits of vari ous measurements required in loss

or efficiency determination. DOE believes that this table should be applicable to dry-type

To ensure compliance with the requirements in this table, DOE is considering

including ' for guidance the following ' partial clause (4.11.1) from ISO. d 9001-1993:

" e supplier shall establish and maintain documented procedures to control, calibrate and

maintain inspection, measuring and test equipment (including test software) used by the

supplier to demonstrate the conformance of product to the specified requirements.

Inspection, measuring and test equipment shall be used in a manner which ensures that

measurement uncertainty is known and is consistent with the required measurement

capability."

Questions and Request for Comments

(1) Are there concerns about applying measurement accuracy requirements to dry-type

o is now done for liquid-immersed transformers, and about inclusion for

guidance of a clause from ISO 9001 -1993 on measurement quality assurance procedures?

.. 

, ' 

transformers~ DOE is considering applying corrections to both tnmsformer types.' 

, 

Ouestions apd ReQuest for Comments 

(I) Are·there concerns .oout applyfug corrections. ifreqwred, to ~rement data of drytype transformers as is already done, for liquid immersed transformers? 

Ia. Requirement for quality u.urance in testing. 

CS7.12.00 provides a table of uncertainty' limits of various mtuurements required in loss 

or efficiency determination.' DOE believes that this table should be applicable to dry-type 

transformers. To ensure compliance with the requirements in this table, DOE is considering 

including for guidancetbe following partial clause (4.11.1),from ISO standard 9001-1993: . , 

"The supplier shaII.establish and maintain documented procedures to controt calibrate and 

.maintaiIl inspection,.measuring and test equipment (mcluding test software) used by the 

supplier to demonstrate the conformance of product to the speci~ed requirements. 

Inspection, measuring and test equipment shall be used in a manner which ensures that . 

, measurement uncertainty is known and is consistent with the required measurement 

capability." . 

. Questions and Request for C~ts 

.(1) Are there conceins about applying measurement accuricy requirements to dry-type 

transformers as is DOW done for liquid-immersed transformers, and about inclusion for 

guidance of a clause from ISO 900 1 ': 1993 on measuremeni q~tY assurance procedures? . " . . 
427 P02 JAN 12 '• 98 16:00

National l Standards a Ta , b

G a i t h u r g, Maryland 9 1.

Telephone; (301)975-2431

fra*Na.! (301)948-5796

Mall: Room B344, Building 220

January 12, 1998

Ms. Kathi Epping

Program Manager

Office of Codes and Standards, EE 43

Department of Energy

1000 Independence Ave. S.W.

Washington, D.C. 20585

Dear Ms. Epping:

Enclosed is a copy of a report "Energy Conservation Program for Consumer. Products; Test

Procedure for Distribution Transformers," draft 5, prepared by the Electricity Division, National

Institute of Standards and Technology (NIST) for inclusion in the Department's notice of

proposed rulemaking for test procedures.

This draft is submitted to DOE for distribution to prospective attendees of the Department's

workshop on distribution transformer test procedures, scheduled for February 10, 1998, and to

other interested parties to stimulate discussion at the workshop and submission of peer review

comments. The material including recommendations in the submitted draft is preliminary and.

may differ from that in the final report.

Since the draft report is of a preliminary nature and has not received full review byNIST, it may,

n.ot be cited and referenced for the purpose other than those stated in this letter.

arues K. Oltboff;.Leader

Electrical Systems Group'

Electricity Division

cc: J. Hill

Enclosure

427 P02 . JAN 12 '·98 1/?:00 

UlamED STATEB DEPAMMENT oF COMMERCII! 

N.Ukmal .~ of Btandllllrds .nd Technology . 

. ~ithenburg. Maryland 2QB99aJO'I· . 

January 12~ 1998 

Ms. ~tbi Epping 

Program Manager. . 

" . Office of Codes and Standatds, EE 43 

Department of Energy· 

1000 Independence Ave. S.W .. 

Washington~ D.C. 20585 

Dear Ms. Epping: .. 

Telaphon.; (lOI )11'15-2431 

pal( Wo.: ·(SOI)!I4S.S7!16 

1'4&11: ltpom B3"'~. BlIlJdins ~:ZO 

Enclosed is a copy Qf a report "Energy Conservation Program for Consumer Products; Test 

procedure for Distrihution Transformers." draft 5, prepared by the Electricity Divisi6n, National 

InStit)J.te of Standards and Technology (NIST) for inclusion in the Department's notice of" . 

proposed rulemaking for test proccdw:cs. 

This ¢aft is submitted to DOE'fo! distribution to prospective attendees ofth~ Department's 

workshop on distribution transformer test procedures, scheduled for February 10, 1998, arid to 

other interested parties to stimulate discussion at the 'Workshop and 'submission of peer review 

comments. The material including recommendations in the submitt~ draft is preliminary. arid 

may differ from that in the .tiDal report. . . .. 

Since the draft report is of a preliminary nature and has not received full revievv by.NIST. it may· . 

not be cited and referenced. for the purpose other than: those stated in this letter. . 

.• SinoerOly,t! ~. 

~lIbOfl;Leadei .. 

Electrical Systems Group'! 

Electricity Di,vision ' 

. cc: J. :fiill 

, Enclosure 

, . 

NISiI 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

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Energy Conservation Program for Consumer Products; Test Procedure for Distribution

Transformers

Draft 5

January 12, 1998

Preamble

(Note: introductory administrative material teen delete 'this draft)

Discussion

The Department of Energy proposes to adopt tes rocedure for distribution transformers.

This test procedure would apply to those pr s covered section 325(g)(5) of the Act ( The

Energy Policy and Conservation Act (SPCA)

1. Test Procedure

The Departme' s consi 'ng incorporate by reference six standards, as referenced in

section 323(b)(5) of the , as a est procedure in Appendix S to Subpart B of 10 CFR part

430. Four of these, constitute the primary references, are national standards prepared by the

Institute of Electrical and Electronics Engineers (IEEE) and approved by the American National

Standards Institute (ANSI): ANSI C57.12.90-1993, "IEEE Standards Test Code for LiquidImmersed Distribution, Power and Regulating Transformers and IEEE Guide for Short Circuit

Testing of Distribution and Power Transformers," ANSI C57.12.91-1995, "IEEE Standard Test

Code for Dry-Type Distribution. and Power Transformers," ANSI C57.12.00-1993, "IEEE

Standard General requirements for Liquid-Immersed Distribution, Power and Regulating

i

NIST DRAFT OF NOPR FOR DISTRmUTION TRANSFORMER TEST PROCEDURE 

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Energy Conservation Program for Consumer Products; Test Procedure for Distribution 

Transformers . 

Draft 5 

January 12, 1998 

Preamble 

(Note: introductory administrative material 

. I 

Discussion 

The Department of Energy proposes to adopt te cedure for distribution transformers. 

. This test procedure would apply, to those pr section 325(g)(5) of the Act (The 

Energy Policy and Conservation Act (EPCA) 

1. Test Procedure 

The Departme· incorporate by reference six standards, as referenced in 

section 323(b)(5) of the as a est procedure in Appendix S to Subpart B of 10 CFR part 

the primary references, are national standards prepared by the 

Institute of Electrical and Electronics Engineers (IEEE) and approved by the American National 

Standards Institute (ANSI)~ ANSI C57.12.90-1993, "IEEE Standards Test Code for LiquidImmersed Distribution, Power and Regulating Transformers and IEEE Guide for Short Circuit 

Testing of Distribution and Power Transformers," ANSI C57.12.91-1995, "IEEE Standard Test 

Code fot Dry-Type Distribution and Power Transformers," ANSI C57.12.00-1993, "IEEE 

Standard General requirements for Liquid-Immersed' Distributi~n, ~ower and Regulating 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

****************************************************************************

Transformers," ANSI C57. 12.01-1989, "IEEE Standard General Requirements for Dry-Type

Distribution and Power Transformers, Including Those with Solid Cast and/or ResinEncapsulated Windings ." The Department also considers incorporating by reference a guide

prepared by the National Electrical Manufacturers Association TP 1-1996, "Guide for

Determining Energy Efficiency for Distribution Transformers ,' it spect to reference

temperatures and measures of energy consumption . Fina he Depart t considers

incorporating by reference a single clause , 4.11.1, in tan rd prepared by the International

Standards Organization (ISO), ISO Standard 9001 - 1993, Quality Systems - Model for quality

assurance in design, development, productio tallation ,servicing," regarding quality

assurance of the test and measuring equipmen

All previously mentioned st ds cons ore information than that applicable to loss

or efficiency testing. Hence, o e a abl causes are incorporated by reference in the draft

DOE test procedure . Any subseque endment to these standards by the standard-setting

organizations (ANSI, E, I ) will not affect the DOE test procedure, which can be.

amended only by DOE. test ocedure will provide results suitable for determining whether

the products comply with the dard levels which may be established by the Act.

Additionally, the Department specifies in the proposed test procedure the following

requirements which either are not found in the cited references or may differ among these

references, but are needed to comply with the Act: ( 1) using transformer efficiency at specified

loading levels as the preferred measure of energy consumptiod; (2) using the same reference

temperature of 20 °C for reporting the no-load losses of liquid-immersed and dry-type

transformers; (3) if the efficiency is selected at lower than the rated loading , using the reference

2

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**************************************************************************** 

Transformers," ANSI CS7.12.01-1989, "IEEE Standard General Requirements for Dry-Type 

Distribution and Power Transformers, Including Those with Solid Cast and/or ResinEncapsulated Windings." The Department also considers incorporating by reference a guide 

prepared by the National Electrical Manufacturers Association , TP 1-1996, "Guide for 

Determining Energy Efficiency for Distribution Transformers,' 

temperatures and measures of energy consumption. Fina t considers 

incorporating by reference a single clause, 4.11.1, in d prepared by the International 

Standards Organization (ISO), ISO Standard 9001-1993, 

assurance in design, development, productio . servicing," regarding quality 

assurance of the test and measuring equipmen 

, All previously mentioned st ore iriformation than that applicable to loss 

or efficiency testing. Hence, 0 

organizations (ANSI, 

amended only by DOE. 

the products comply with the 

causes are inporporated by reference in the draft 

endment to these standards by the stand~d-setting 

) will not affect the DOE test proc,edure, which can b~. 

ocedure will provide results suitable for determining whether 

dard levels which may be established by the Act. 

Additionally, the Department specifies in the proposed test procedure the following 

requirements which either are not found in the cited references or may 'differ among these 

references, but are needed to comply with the Act: (1) using transformer efficiency at specified 

loading levels as the preferred measure of energy consumptiorl; ,(2) using the same reference 

temperature of 20°C for reporting the no-load losses of liquid-immersed and dry-type 

transformers; (3) if the efficiency is selected at lower than the rated loading, using the reference 

2 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

temperature for load losses that approximates the temperature rise at new loading conditions (as

opposed to using temperature rises as in ANSI standards for rated nameplate loading); for

example, if loading levels such as those in NENIA TP 1 are selected, reporting of efficiency of

liquid-immersed transformer at 50% of the rated load and the refe temperature 55'C for

load losses; reporting of efficiency of dry-type transformers ra \ **d fo . edium voltages, 1201 volts

and above, at 50% of the rated load and the reference to ature of 7 for load losses;

reporting of efficiency of dry-type transformers rated r 1 voltages, up to 1200 volts, at 35%

of the rated load and the reference temperature of 75 ° C load losses; (4) correcting the

measured load loss data of dry-type transfo for phase le errors in the measuring

equipment as required in ANSI standards for

significant relative to required meas

data of dry-type transformers t

liquid-immersed transformers, if such

accuracy; (6) measurin

sed transformers, if such errors are

pnt acc ; (5) correcting the measured no-load loss

erature of 20°C as required in ANSI standards for

correction is significant relative to required measurement

t e transformers to the same accuracy as specified for

The test procedure inv es the measurement of electric power consumed by the

transformer in the form of no-load and load losses, as well as'determination of certain other

quantities. needed to establish the test conditions : temperature of the windings and the core;

current, voltage, frequency and waveform of voltage, and direct current resistance of the

windings. Certain quality assurance procedures necessary to ensure reliable test data'are available.

in ISO. 9001- 1993 and are recommended as examples in this DOE test procedure.

In summary, the considered DOE test procedure retains the same measurements of losses

, NISI DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

***********************************************************************~  

temperature for load losses that approximates the temperature rise at new loading conditions (as 

opposed to using temperature rises as in ANSI standards for rated nameplate loading); for 

example, if loading levels such as those in NEMA TP 1 are selected, reporting of efficiency of , . 

liquid-immersed transformer at 50% of the rated load and the refl temperature 55°C for 

load losses; reporting of efficiency of dry-type transformers ra 

and above, at 50% of the rat~dload and the reference te for load losses; 

reporting of efficiency of dry-type transformers rate voltages, up to 1200 volts, at 35% 

of the rated load and the reference temperature of 75°C ad losses; (4) correcting the 

measured load loss data of dry-type transfo e errors in the measuring 

equipment as required in ANSI standards for I sed transformers, if such errors are 

sigQificant relative to required meas ; (5) correcting the measured no-load loss 

data of dry-type transformers t erature of 20c

C as required in ANSI standards for 

liquid-immersed transformers" if sucH orrection is significant relative to required measurement 

~ccuracy; (6) measuri e transformers to the same accuracy as specified for 

liquid-immersed transfo 

es the 'measurement of electric power consumed by the 

transformer in the form of no-load and load losses, as well as'determination of certain other 

quantities ,needed to establish the test conditions: temperature of the windings and the core; 

- current, voltage, frequency and waveform of voltage, and direct current resistance of the 

windings. Certain quality assurance procedures necessary to ensure reliable test data 'are available 

in ISO 9001- 1993 and ar:e recommended as examples in this DO~ test procedure. 

In summary, the considered DOE test procedure retains the same measurements oflosses 

3 ' 
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** *********************************k*********** *************** **************

as specified in the current versions of the previously cited ANSI standards, but requires some

harmonization of requirements for the two types of transformers; additional computation is

required to convert the data to reference temperatures consistent with reporting of efficiency at

lower than the rated loading.

2. Reference Conditions

DOE is considering to establish certain reference nditions for reporting the test results.

For the purpose of this DOE test procedure iency of li id-immersed transformers is

reported at 50% of the rated load and the refe n e rature of 20°C for no-load losses and

55°C for load losses; efficiency of

and above, is reported 'at 50%

load losses and 75°C for load losses;

up to 1200 volts, is re

no-load losses and 75°C

computation should be adjust

ers operated at medium voltages, 1201 volts

and the reference temperature of '20°C for nociency of dry-type transformers operated at low voltages,

e rated load and the reference temperature of 20°C for

sses'. The measured no-load and load losses used in efficiency

to the stated reference conditions, if such adjustments are

significant relative to the required measurement accuracy.

Under the current industrial practice, the load losses of liquid-immersed transformers are

reported at the rated load and the reference temperature of 85°C, as specified by ANSI

'Establishing of specific, loading levels belongs to the energy conservation standard, but

correction of measurement data to new reference conditions is a part of the test procedure. The

loading levels of the NEMA. TP i are used here . only as examples.

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

**************************************************************************** 

as specified in the current versions of the previously cited ANSI standards, but requires some 

harmonization of requirements for the two types of transfonners; additional computiltion is 

required to convert the data to reference temperatures consistent with reporting of efficiency at, 

lower than the rated loading. 

, 2. Reference Conditions 

DOE is considering to establish certain reference ·tions for reporting the test results. 

For the purpose of this DOE test procedure Id-immersed transformers is 

reported at 50% of the rated load and the refe rature of 20°C for no-load losses and 

55°C for load losses; efficiency of ers operated at medium voltages, 1201 volts 

and above, is reported at 50% ad and the reference temperature of' 20°C for noload losses and 75°C for load losses; iency of dry-type transformers operated at low voltages, 

up to 1200 volts, is re e rated load and the reference temperature of 20°(: for 

no-load losses and 75°C sses1

• The measured no-load and load losses used in efficiency 

computation should be adjust to the stated reference conditions, if such adjustments are 

significant relative to the, required measurement accuracy. 

Under the current industrial practice, the load losses of liquid-immersed transformers are 

. reported at the rated load and the reference temperature, of 85°C, as specified by ANSI 

lEstablishing of specific, loading levels belongs to the energy conservation standard, but 

correction of measurement data to new reference conditions is a part of the test procedure. The, 

loading levels of the NEMA TP.l are used here,only as examples. 

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****************************************************************************

057.12.00. This reference temperature is based on ambient temperature of 20°C and the

temperature rise of 65°C. The load losses of dry-type transformers are reported at the rated load

and, based on the insulation system used, at one of five specified temperature rises in addition to

ambient temperature of 20°C, as specified by ANSI 057.12.01. T ultant reference

temperatures are: 80, 100, 135, 150, and 170°C., ANSI stand s .12.90 and C57.12.91

provide an identical algorithm for converting the measur ad loss va to specified reference

temperatures.

For no-load losses of liquid-immersed transforms ANSI 057.12. 00 specifies the

reference temperature of 20°C, thus approxi ftg ambient nditions. Additionally, ANSI

057.12.90 provides an algorithm for converti

temperature to that at the reference erature`.No reference temperature is specified for the

no-load losses of the dry-type t

The NEMA Guide TP 1, 199 ecommends minimum efficiencies and the following

reference conditions fo istribut tra formers: for liquid-immersed transformers the reference

loading is 50% of rated to and t reference temperatures are 20°C and 85°C for no-load and

load losses, respectively; fort medium-voltage dry-type transformers, the reference loading is

50% of the rated load and the reference temperatures are 20°C for no-load losses and 75°C for

load losses; for the low-voltage dry-type transformers, the reference loading is 35% of the rated

load and the reference temperatures are 20°C for no-load losses and 75°C for load losses.

The previous examples illustrate considerable diversity in the reference conditions as

specified in the existing consensus standards. To enhance uniformity in requirements and facilitate

comparison of products using liquid-immersed and dry-type insulations, the Department is

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

 .** ************* •• ****************************************************** 

CS7.12.00. This reference temperature is based on ambient temperature of 20°C and the 

temperature rise of 65°c. The load losses of dry-type transfonners are reported at the rated load 

and, based on the insulation system used, at one of five specified temperature rises in addition to 

ambient temperature of 20°C, as specified by ANSI CS7.12.01. 

temperatures are: 80, 100, 13S, ISO, and 170°C .. ANSI stand 

provide an identical algorithm for converting the measur to specified reference 

temperatures. 

For no-load losses of liquid-immersed transfonn SI CS7.12.00 specifies the 

reference temperature of 20°C, thus appro' nditions. Additionally, ANSI 

CS7.12.90 provides an algorithm for converti loss value measured at another 

temperature to that at the reference reference temperature is specified for the 

no-load losses of the dry-type t . . 

commends minimum efficiencies and the following 

reference conditions fc fonners: for liquid-immersed transfonners the reference 

loading is SO% of rated 1 reference temperatures are 20°C and 8SoC for no-load and 

load losses, respectively; for t medium-voltage dry-type transformers, the reference l~ading is 

SO% of the rated load and the reference temperatures are 20°C for no-load losses and 75°C for 

. load losses; ror the low-voltage dry-type transformers, the reference loading is 35% of the rated 

load and the reference temperatures are 20°C for no-load losses and 75°C for load losses. 

The previous examples illustrate considerable diversity in the reference conditions as' 

specified in the existing consensus standards. To enhance unifonnity in requirements and facilitate 

comparison of products using liquid-immersed and dry-type insulations, the Department is 

5 
KIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

considering 20°C as the reference temperature for no -load losses of both transformer types, 55°C

as the reference temperatures for load losses of liquid-immersed. transformers operating at 50% of

the rated load, and 75°C as the reference temperature for load losses of dry-type transformers

operated at 50% and 35% of the rated load.

Three considerations influenced the selection of these ere a temperatures : to obtain'

uniformity in reference conditions, to have the reference itions that reflect the actual

operating conditions, to maintain consistency with th ra es of the current consensus

standards as much as possible . Satisfying all three state nditions was not practical or even

possible, because of the previously mention ersity in th xisting practice. The proposed

reference temperature for no-load losses of bo es ransformers is 20°C which is consistent

with C57.12. 00 and TP 1, but not O 57.12. hich does not specify the reference

temperature for no-load losses ry- an formers. This. reference temperature is close to

the ambient temperature, readily avai le for loss measurement when the transformer is cold, but

does not represent ope ing con ion However, the changes in the core losses due to

temperature are small, q'u d as x 10' per unit per °C,' and will have small effect on the

resultant calculated efficiency.,

If the measure of transformer energy consumption in a potential future energy

conservation standard is efficiency at less than full-rated or nameplate loading, it is proper to

adjust the reference temperature for load losses as done in TP-1 for dry-type transformers. It is

proposed that in the DOE test procedure the reference temperature be lowered also for the load

losses of liquid-immersed transformers from 85 °C to 55°C to better approximate the conditions of

the actual use and extend the same approach to both types of transformers. The conversion of

6

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**************************************************************************** 

considering 20°C as the reference temperature for no-load losses of both transformer types, 55°C 

as the reference temperaiures for load losses of liquid-immersed. transformers operating at 50% of 

the rated load, and 75°C as the reference temperature for load losses of dry-type transformers 

operated at 50% and 35% of the rated load. 

Three considerations influenced the selection of these to obtain' 

uniformity in reference conditions, to have the reference reflect the actual 

operating conditions, to maintain consistency with th ,s of the current consensus 

standards as much as possible. Satisfying all three state ditions was not practical or even 

possible, because of the previously mention xisting practice. The proposed 

reference temperature for no-load losses ofbo ransformers is 20°C which is consistent 

with C57.12.00 and TP I, but not hich does not specify the reference 

temperature for no-load losses ormers. This reference temperature is close to 

the ambient temperature, readily avat e for loss measurement when the transfornier is cold, but 

does not represent op However, the changes in the core losses due to 

temperature are small, qu" x 10-4 per unit per °C,' and will have small effect on the 

resultant calculated efficiency 

Ift~e measure of transformer energy consumption in a potential future energy 

, , 

conservation standard is efficiency at less than full-rated or nameplate loading, it is proper to 

. adjust the reference temperature ror load losses as done in TP-l for dry-type transformers. It is ' 

proposed that in the DOE test proced~re the reference temperature be lowered also for the load 

'losses of liquid-immersed transformers from 85°C to 55°C to better approximate the conditions of 

the actual use and extend the same ap'proach to both types of transformers. The coilVersion of ' 

6 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

load losses to a different reference temperature is a computational operation using a well

established algorithm published in ANSI C57,12.90 and ANSI C57.12.91.

For load losses of dry-type transformers, TP-1 recommends a single reference temperature

of 75°C as a substitute for five temperatures at the rated load corr p ding to five insulation

classes. To assess soundness of such a selection, reduced ope tin mperatures were calculated

at 50% and 3S% of rated load for all five temperature cla of dry-typ ' sulation and for liquidimmersed insulation. The relationship whereby the t per re rise (AT) is proportional to the

0.8th power of the dissipated power (W) was used fort calculation. Thus, AT = kW-, where

k is a constant. The assumption was made t the rated d 75% of dissipated power is the

load loss, the remainder no-load (core) loss.

The results are summarized ' ble 1-A both the 50% and 35% of the rated loads. It

is instructive to note that for d e tr ormers out of 10 estimated reference temperatures

five are below 75°C, four are above one exactly on. Thus, the selected value in TP-1

represents a

reasonable compromise, eeciallf each of the 10 groups were to have similar installed kVA

capacity.

It should be noted that alternative choices for reference temperatures are feasible, for

example, to retain the same reference temperatures for the load losses as in ANSI C57.12.00 and

ANSI 057.12. 01, but to make an allowance in the minimum efficiency requirement for the

possible overestimation of the magnitude of losses using the temperature corresponding to the

rated load. We invite comments by the interested groups and individuals on this matter.

7

I

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**************************************************************************** 

load losses to a different reference temperature is a computational operation using a well 

established algorithm published in ANSI C57.12.90 and ANSI C57.12.91. 

F or load losses of dry-type transformers, TP-l recommends a single reference temperature 

6f75°C as a substitute for five temperatures at the rated load corr ing to five insulation 

classes. To assess soundness of such a selection; reduced ope 

at 50% and 35% of rated load for all five temperature cl ulation and for liquidimmersed insulation. The relationship whereby the t re rise (6. T) is proportional to the 

0.8th power of the dissipated power (W) was used for t culation. Thus, 6.T = kWO·8

, where 

k is a constant. The assumption was made t d 75% of dissipated power is the 

load loss, the remainder no-load (core) loss. 

The results are summarized . both the 50% and 35% of the rated loads. It 

is mstructive to note that fbr d ers out of 10 estimated reference temperatures 

five are below 75°C, four are above Thus, the' selected value in TP-l 

represents a 

reasonable compromise, f each of the 10 groups were to have similar installed kVA 

capacity. 

It should be noted that alternative choice.s for reference temperatures are feasible, for 

example, to retain the same reference temperatures for the load losses as in ANSI C57.12.00 and 

ANSI C57.12.01, but to make an allowance in the minimum efficiency requi~ement for the 

possible overestimation of the ~agnitude oflosses using the temperature corresponding to the , " 

rated load. We invite comments by the hiterested groups and individuals on this matter. 

7 
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3. Basic Model

With regard to the residential appliance programs, 10 CFR 430.2, the term "basic model"

is defined as follows: "Basic model means all units of a given type of covered product (or class

thereof) manufactured by one manufacturer and [with respect to hers, for example} which

do not have any differing physical and functional characteristi tha ect energy consumption."

DOE is considering a similar definition for transfo rs: "Basic del means all units of a

given type of covered equipment (or class thereof) ufa ured by a single manufacturer and,

with respect to distribution transformers, which have the a rating, have electrical

characteristics that are essentially identical, o not have y differing physical or electrical

characteristics which affect energy consumpti " For the purpose of this definition,

"rating" means standard output po ting, sui,s one of those tabulated in NEMA TP 1,

tables 4-1 and 4-2, reproduced as s 1 and 2 . These power ratings are also the preferred

ratings from ANSI C57.12.00-1993 liquid-immersed transformers and ANSI C57.12.01-1989

for dry-type transform

The Department cipat that this definition will separate the various types of

transformers according to the ominal power (kVA) rating, insulation type (liquid-immersed. or

dry-type), number of phases (single or three) and the voltage rating range (medium-voltage and

low-voltage for dry-type transformers).

4. Measures of Energy Consumption

DOE is proposing in today's notice three interrelated measures of energy consumption:

8

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***********************************************************~**************** 

3. Basic Model 

With regard to the residential appliance programs, 10 CFR 430.2, the term "basic model" 

is defined as follows: "Basic model means all units of a given type of covered product (or class 

thereof) manufactured by one manufacturer and [with respect to hers, for example] which 

do not have any differing physical and functional'characteristi 

DOE is considering a similar definition for trans:fi del means all units of a 

given type of covered equipment (or class thereof) red by a single manufacturer and, 

with respect to distribution transformers, which have the rating, have electrical 

characteristics that are essentially identical, y differing physical or electrical 

characteristics which affect energy consumpti cy." For the purpose of this definition, 

"rating" means standard output POWfillllflilt one of those tabulated in NEMA TP 1, 

tables 4-1 and 4-2, reproduced 1 and 2. These power ratings are also the preferred 

ratings from ANSI CS7.12.00-1993 i tiid-imrnersed transformers and AN~I CS7.12.01-1989 

for dry-type transform 

that this definition will separate the vario~s types of 

transformers according to the ominal power (kV A) rating, insulation type (liquid-immersed. or 

dry-type), number of phases (single or'three) and the voltage rating range (medium-voltage and 

low-voltage' for dry-type transformers). 

4. Measures of Energy Consumption 

DOE i~ proposing' in today's notice three interrelated measures ofener~ consumption:. 

8 
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(a) total transformer losses, (b) transformer efficiency, and (c) estimated annual energy

consumption (EAEC). All these measures are tentatively considered using loading parameters of

NEMA TP 1 at 50% of the-rated load for liquid-immersed and medium-voltage dry-type

transformers and at 35% of the rated load for low-voltage dry-typ r sformers. DOE considers

efficiency as the preferable measure of energy consumption. in stry practice, as required by

the cited ANSI standards, has been to measure and repo nsformer 1 s. DOE believes that

for energy conservation purposes efficiency is a bett ea re as it is a normalized measure and

allows trade-offs between the two types of losses. The artment would like comments on this

measure of energy consumption and the pra ty of its us or the DOE test procedures.

The Code of Federal Re tions (CFR), in 10 CFR Part 430 §430. 23 outlines in

general terms the sam g plan co Hance testing. For example, under §430.23 (q)(1), "For

each basic model of fluor ent -la p ballasts, as defined in paragraph (14) of §430.2, a sample of

sufficient size, no less than fo shall be tested to insure that ... (ii) Any represented value of the

ballast efficiency factor or other measure of energy consumption of a basic model for which

consumers would favor a higher value shall be no greater than the lower of (A) the mean of the

sample or (B) the lower 99 percent confidence limit of the true mean divided by 0.99."

The sampling plan for enforcement testing is provided in 10 CFR Part 430 §430.70,

Appendix B. This sampling plan is based on the statistical t-test yielding 97.5 percent probability

of obtaining a determination of compliance when the true mean efficiency is equal to the

9

. NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

*****.*****************.*.**.************** •••••• ** ••• ********************** 

(a) total transformer losses, (b) transformer efficiency, and (c) estimated annual energy 

consumption (EABe). All these measures are tentatively considered using loading parameters of 

NEMA TP 1 at 50% of the· rated load for liquid-immersed and medium-voltage dry-type 

transformers and at 35% of the rated load for low-voltage dry-ty sformers. DOE considers 

efficiency as the preferable measure of energy consumption. try practice, as required by 

. the cited ANSI standards, has been to measure and repo s. DOE believes that 

for energy conservation purposes efficiency is a bett e as it is a normalized measure and 

allows trade-offs between the two types oflosses. The ment would like comments on this 

measure of energy consumption and the pra or .the DOE test procedures. 

5. Number of Units to be Tested 

'ons (CFR), in 10 CFRPart 430 §430.23 outlines in 

Hance testing. For example, under §430.23 (q)(l), "For 

p ballasts, as defined in paragraph (14) of §430.2, a sample Of 

sufficient size, no less than fo hall be tested to insure that ... (ii) Any represented value of the 

ballast efficiency factor or other measure of energy consumption of a basic model for which 

consumers would favor a higher value shall be no greater than the lower of (A) the mean of the 

sample or (B) the lower 99 percent confidence limit of the true mean divided by 0.99." 

The sampling plan for enforcement testing is provided in lOCFR Part 430 §430.70, 

Appendix B. This sainpling plan is based on the statistical t-test yielding 97.5 percent probability 

of obtaining a determination of compliance when the true mean efficiency is equal to the 

9 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

applicable standard.

At this time the Department is considering one of two sampling plans for compliance

testing of distribution transformers:.

1) The plan described in §430.23, using the lower'95 perc dence limit, but without

s p e c i f y i n g the minimum number of units in the sample (a mini fm .two units is implicitly

required to estimate the confidence limit.)

"A sample shall be selected and tested camp o nits which are production units, or

are representative of production units of the basi odel being tested and shall meet the

following applicable criteria. For ea is model istribution transformers, as defined

in §430.2, a sample of sufficient size s t to insure that any represented value of

transformer efficiency shall greate h t the lower of (A) the mean of the sample or

(B) the lower 95% co ce of the estimated true mean divided by 0.999.

The divisor, 0.999, is based on the s ercent loss tolerance specified in Table 19, ANSI

C57.12.00 and in an id ical tab in SI C57.12.01.

2) A modified ver oft sampling plan for enforcement testing as in 10 CFR Part 430

§430.70, Appendix B. This s pling plan outlined below is based on the statistical t-test yielding

90 percent probability of obtaining a determination of compliance with the target efficiency when.

the true mean efficiency is equal to the target efficiency.

"A sample of no fewer than five units shall be selected. at random and tested. The measured mean

efficiency of the sample shall be in compliance with the mandated minimum efficiency applicable.

to the basic model. The compliance shall be demonstrated by the following sampling plan and

analysis.

10

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

**************************************************************************** 

applicable standard. 

At this time the Department is considering one of two sampling plans for compliance 

testing of distribution transformers: 

1) The plan described in §430.23, using the lower'95 per dence limit, but without 

specifying the minimum number of units in the sample (a mini . 

required to estimate the confidence limit.) 

"A sample shall be selected and tested comp . "ts which are production units, or 

are representative of production units ofthe basi el being tested and shall meet the 

following applicable criteria. For ea istribution transformers, as ddined 

in §430.2, a sample of sufficient size s to insure that any represented value of 

transformer efficiency shall t the lower of (A) the mean of the sample ot 

(B) the lower 95% co " of the estimated true mean divided by 0.999." 

The divisor, 0~999, is based on the s ercent loss tolerance specified in Table 19, ANSI 

C57.12.00 and in an id 

sampling plan for enforcement testIng as in 10 CFR Part 430 

piing plan outlined below is based on the statistical t-test yielding 

• 

90 percent probability of obtaining a determination of compliance with the target efficiency when 

the true mean efficiency is equal to the target efficiency. 

"A sample of~o fewer than five units shall be selected.at random and tested. The measured mean 

efficiency of the sample shall be in compliance with the mandated minimum efficiency applicable. 

to the basic model. The compliance shall be demonstrated by the following sampling plan and 

analysis. 

10 
MIST DRAFT OF NOI R FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

Step 1.

Step 2.

The first .sample size (n,) must be 5 or more units.

Compute the mean (Xj) of the ured efficiency of the nl units in the first

Step 3: Compute the sample standar ation (SI).the measured efficiency, of the nl

units in the first sample as folio

or (SE(X))'ofthe mean efficiency of the first sample as

SE(X,)=

nl

Step 5'. Compute the lower control limit (LCL,) for the mean of the first sample using the

applicaple mandated efficiency (ME) as the desired mean as follows:

11

-- .. 

-' 

.. NIST DRAFT OF. NOPR FOR DISTRlBUTION TRANSFORMER TEST PROCEDURE 

.•• $* •• "''''**'''.''''*.''' •••• *** •• * •••• '''****'''Ii<*'''*'''*'''''' ••••••.• '''*"''''''''''****** ••• *'''**'''**''''''* 

The first Sample size (111) m~st be 5 or more units. 

,. . Step 1.. 

Step 2. Compute the mean (XJ

) of the measured efficiency of the "1 urnts in the first 

.\ 

Sample as follows: 

.where X; is the efficiency of unit i. 

. Step 3.' Compute the sample standar the m~asured efficiency ,of the nl 

. Step 4 .. de or (SE(X1»ofthemea,n efficiency of the first sample as .' '. '. 

follows: 

.. 

'" . ./ 

Step 5. ,Compute the lower control limit (tCL1) for the mean of the first sample using the . . 

applicapJe mandated efficiency (ME) as the desired mean as follows: 

\ 

.11 .,. - ... , 
NIST DRAFT OF NOPR. FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

LCLI =ME-tSE(XI).

Here t is the 10th percentile of a t-distribution for a sample size of . n, and yields a

90 percent confidence level for a one-tailed t test.

Step 6. Compare the mean of the first sample (X) wit he er control limit (LCL) to

determine one of thefollowing:

(i) If the mean of the first sample el the lower control limit, then the,

basic model is in noncompliance testing is at an end.

(ii) If the mean is equal t eater tha a lower control limit , no final

determination of compl c r compliance can be made; proceed to

Step 7. Determine the r. a sample size (n) as follows:

where S , and t ve the values used in steps 3 and 5, respectively. The factor

106 - 0.06ME

ME(6 - 0.06ME)

is based on a 6 percent tolerance in the total losses. Given the value of n,

determine one of the following:

(i) If the value of n is less than or equal to ni and if the mean efficiency of the first

sample (X,) is equal to or. greater than the lower control limit (LCL) , the basic

12

T

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

********************************************'******************************** 

Step 6. 

Step 7. 

LC1:1 =ME-tSE(~). 

Here t is the lOth percentile of a t-distribution for a sample size or .n] and yields a 

90 percent confidence level for a one-tailed t test. 

Compare the mean of the first sample (X]) wit 

determine one of thefollowing: 

(i) If the mean of the first sample' the lower controllimit~ then the. 

(li) 

Step 7. 

Determine the r 

e lower control limit, no final 

compliance can be made; proceed to 

1(106 ~ 0.06ME)f 

"ME(6 - 0.06ME) 

ve the values used in steps' 3 and 5, respectively. The factor ' 

106 - 0.06"ME 

ME(6 - 0.06ME) 

is based ona 6 percent tolerance in the total losses. Given the value of n, 

determine one of the following: 

(i) If the value ofn is less than or equal to n1 and if the mean efficiency of the first 

sample (X) is equal to or gr~ater than the lower control limit (LCL1) , the basic 

12 . 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

model is in compliance and testing is at an - end.

(ii) If the value of n is greater than n,, the basic model is in noncompliance. The

size of a second sample n2 is determined to be the t integer equal to or

greater than the difference n - n,.: If the value n2 . , calculated is greater than 20

- n,, set n2 equal to 20 - nl.

Step S. Compute the combined mean (X2) of el ency of the n, and n2 units of the

combined first and second samples as foil

+"2

)) of the mean efficiency of the n, and n2 units

in the combined first 04 second samples as follows:

(Note that S, is the value obtained above in Step 3.)

Step 10. Set lower control limit (LCL2) to,

LCL2 = ME-tSE(X2),

where t has the value obtained in Step 5 and compare the combined sample mean

13

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

**************************************************************************** 

Step 8. 

Step 9. 

Step 10. 

model is in compliance and testing is at an end. 

(ii) If the value ofn is greater than nb the basic model is in noncompliance. The 

size of a second sample n2 is determined to be the t integer equal to or 

greater than tbe difference n - nl . If the value 

~ompute the combined mean (X2) of 

"combined first and second samples as foIl 

iency of the n1 and n2 units of the 

Compute the st 2» of the mean efficiency of the n1 and n2 units 

in the combined first 

(Note that' SI is the value obtained above in Step 3.) 

, Set lower control limit (LC~) to, 

wh~r~ t has the value obtained"in Step 5 and compare the combined sample mean 

13 
KIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

(X2) to the lower conmtrol limit (LCL2) to fine one of the following:

(i) If the mean of the combined sample (X2) is less e lower control limit

(LCL,2), the basic model is in noncompliance tes is at an end..

(ii) If the mean of the combined sample (X equal to o eater than the lower

control limit (LCL2), the basic model ' c pliance and testing is at an end."

For the enforcement testing of transformers the artment is considering a. plan similar

to 2) above but changing the probability of nation of a compliance from the 10th

percentile to the 2.5th percentile.

While most distribution trap ers are l tested for losses, as a contractual purchase

requirement, ANSI standards d t re su h testing. ANSI 057: 12.00 does not require load

loss measurements on routine basis transformers rated for 500 kVA and smaller; only design

tests are required. AN C.57. 1 1 d s not require no-load and load loss measurements on

routine basis for transfos rate for 500 kVA and smaller; sampling approach is required for

no-load loss measurements aniffiesign tests for load loss measurements.

Manufacturers who produce fewer than 5 units of a basic model during a 180 calendar day

period may use the actual measured mean of all transformers of a particular basic model tested

during that period as the representative value. In lieu of analyzing data that are based on

sampling, manufacturers who measure losses of all transformers of a particular basic model may

use mean value of all units of a particular basic model during the previous 180 day period as the

representative value. .

14

. NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

**************************************************************************** 

, 

. (X2) to the lower conmtrollimit (LC~) to fine one of the following: 

(i) Ifthe mean of the combined sample (X;) is less 

(LCLJ, the basic model is in noncompliance 

e lower control limit 

(ii) If the mean of the combined sample(X eater than the lower 

control limit (LCL2), the basic model' pliance and testing is at an end." 

For the enforcement testing of transformers the ment is considering a. plan similar 

to 2) above but changing the probability of e compliance from the 10th 

percentile to the 2.5th percentile. 

tested for losses, as a contractual purchase 

requirement, ANSI standards d h testing. ANSI C57:12.00 does not require load 

loss measurements on routine basis ansformers rated for 500 kVA and smaller; only design 

s not require no-load and load loss measurements on 

routine basis tor transfo for 500 kVA and smaller; sampling approach is required for 

no-load loss measurements esign tests for load loss measurements. 

Manufacturers who produce fewe~ than 5 units of a basic model during a 180 calendar day 

period may use the actual measured mean of all transformers of a particular basic model tested 

during that period as the representative vwue .. In lieu of analyZing data that are based on 

sampli~g, manufacturers who measure losses ?f all transformers of a particu~ar basic model may 

use mean value of all units of a particular basi~ model during the previous 1,80 day period as the. 

representative value. 

14 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

TEST PROCEDURE

PART 430-ENERGY CONSERVATION PROGRAM FOR CONS UMER PRODUCTS

1. The authority citation for Part 430 continues to. read as

Authority: Energy Policy and Conservation Act, Title III, Pa , ended by the National

Energy Conservation Policy Act, Title IV, Part 2 by the nal Applia Energy Conservation

Act of 1987, and by the National Appliance Conserv on .nendments of 1988 (42 U.S.C. 6291-

6309).

2. Section 430.2 is amended by adding

transformers, as follows:

§ 430.2 Definitions.

del" definition for distribution

"Basic model me s all 'ts of a given type of covered equipment (or class thereof)

manufactured by a single man cturer andWith respect to distribution transformers, which have the same rating, have electrical

characteristics that are essentially identical, and do not have any differing physical or electrical

characteristics which affect energy consumption or efficiency." For the purpose of this definition,

"rating" means standard output power rating, such as one of those tabulated in NEMA TP 1,

tables 4-_1 and4-2. .

15

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

••••••••••••••••••••••••••••••••••••••••••••• *.,'*', •••••• ,""', •••• " ••••• 

TEST PROCEDURE 

PART 430-ENERGY CONSERVATION PROGRAM FOR CONSUMER PRODUCTS 

1. .The authority citation for Part 430 continues to. read as 

Authority: Energy Policy and Conservation Act, Title TIL, Paended by the National 

Energy Conservation Policy Act, Title IV, Part 2 by the Energy Conservation 

Act of 1987, and by the National Appliance Conse endments of 1988 (42 U.S.C. 6291-

6309). 

2. Section 430.2 is amended by adding del" definition for distribution 

transformers, as follows: 

§ 430.2 Definitions. 

• * * * • 

ts of a given type of covered equipment (or class thereof) 

manufactured by a single ma 

* * • * • 

With respect to distribution transformers, which have the same rating, have electrical 

characteristics that are essentially identical, and do not have any differing physical or electrical 

characteristics which affect energy consumption or efficiency." For the purpose of this definition, 

"rating" means standard output power rating, such as one of those tabulated in NEMA TP ~, 

tables 4 -.1 and 4 - 2. 

15 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

Distribution transformer means a transformer for transferring electrical energy from a

primary distribution circuit to a secondary distribution circuit, or to consumer's service circuit, or

between circuits on the consumer's premises. For the purpose of As OE test procedure, the

transformers with the following ratings are included : primary to f 480 V to 35 kV,

secondary voltage of 120 V to 480 V, rated load for Iiqu' ersed tr. ormers from 10 WA

to 2500 WA, for dry-type transformers from 10 kV;o 20 kVA.

Efficiency of a transformer means j

ib

o of the u output power to the total input

power. In practice, the useful output powsubtracting the total losses of the

transformer from its input.power. ntransformer varies with the output power as a

result of varying load losses.

Dry-type transf er mIs a ansformer in which the core and coils are immersed in a

gaseous or dry-compoun sulati medium.

Liquid-immersed transformer means a transformer in which the core and coils are

immersed in an insulating liquid.. .

Load losses of a transformer mean those losses which are incident to the carrying of a

specified load. Load losses include ohmic (12R) loss in the windings due to load and eddy

currents; stray loss due to leakage fluxes in the windings, core clamps, and other parts and the

16

Li

NIST DRAFT, OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

****************************'*****************************************"'****** 

* * '" >I< * 

Distribution transjormer means a transformer for transferring electrical energy from a 

primary distribution circuit to a secondary distribution circuit, or to consumer's service circuit, or , 

'between circuits on the consumer's premises. For the purpo~e of 

, " I OE test procedure, the 

tranSformers with the following ratings are included: primary 

secondary voltage of 120 V to 480 V, rated load for liqu,· .... "'UH .. I' onners from 10 kV A 

, to 2500 k V A, for dry-type'transformers from 10k V 

* '" >I< >I< >I< 

EffiCiency of a transformer means t output power to the total input 

power. In practice, the useful output power i subtracting the total losses of the 

transformer from its input ,power." ..... ~ sformer varies with the output power as a 

result of varying load losseS. 

>I< >I< * *' * 

ansformer in which the core and coils are immersed in a 

gaseous or dry-compoun medium. 

>I< '" 'iI< >I< >I< 

'Liquid-immersed transformer means a'transformer in which the core and coils are 

immersed in an insulating liquid,. 

'" '" *. '" '" 

Loadlosses of a transformer mean those losses which are inciden~' to the carrying of a , . ' 

specified load. Load losses include ohmic (I2R) loss in the windings due to load and eddy 

currents; stray loss due to leakage fluxe,s in the windings,' core clamps, and oth~r parts and the 

16 
MIST DRAFT OF NOPR. FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

****************************************************************************

loss due to circulating currents in parallel windings or in parallel winding strands . Load losses

vary quadratically with the output current and, hence, with the output power.

* * * * *

Low-voltage dry-type transformer means a transformer jh rimary voltage rated at

1.2 kV and below.

* * * * *

Medium-voltage dry-type transformer meaqffi trasformer with a primary voltage rated

above 1.2 kV.

* * * * *

No load (excitation) losses ansfo er mean those losses which are incident to the

excitation of the transformer. oad s i c ude core loss, dielectric loss, conduction . loss in

the windings due to exciting current, d conduction loss due to the circulating currents in parallel

windings. These losse ary wit he e itation voltage.

* * ,* * *

Total losses of a trans er mean the total of the no-load and load losses, excluding

losses due to accessories, such as cooling fans.

* * * * *

Transformer means a static electromagnetic device consisting of a winding, or two or

more coupled windings, with a magnetic core for introducing inductive coupling between electric

circuits. Transformers are extensively used in electric power systems to transfer power by

electromagnetic induction between circuits at the same frequency , usually to change the

17

NIST DRAFT OF NOPR. FOR DISTRlBUTION TRANSFORMER TEST PROCEDURE 

**************************************************************************** 

loss due to circulating currents in parallel windings or in parallel winding strands. Load losses 

vary quadratically with the output Current and, hence, with the output power. 

* * * * * 

Low-voltage dry-type transfonner means a transformer 

1.2 kV ~d below. 

* * * ... ... 

Medium-voltage dry-type transformer ormer with a primary voltage rated 

above 1.2 kV. 

* ... * * * 

No-load (excitation) losses mean those losses which are incident to the 

excitation of the transformer. . c ude core loss, dielectric loss, conduction, loss in . 

the windings due to excitin conduction loss due to the circulating currents in parallel 

windirigs. These losse 

... * ,II< II< * 

er mean the total of the no-load and load losses, excluding 

losses due to accessories, such as cooling fans. 

... ... * * * 

Transfonner means a static electromagnetic device consisting of a winding, or two or 

more coupled windings, with a magnetic core for introducing inductive coupling between electric 

circuits. Transformers are extensively used in electric power systems to transfer power by 

electromagnetic induction between ~ircuits at the same :frequency, usually to ·change the 

17 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

****************************************************************************

amplitudes of the voltage and current.

* * * *

3. Section 430.22 is amended by adding new paragraph(s) ows:

§ 430.22 Test procedures for measures of energy con tion.

* * * * *

(s) Distribution Transformers. (1) Total power losses; a ressed in kilowatts, of a liquidimmersed or medium-voltage dry-type trans fftr operated 50% ofthe rated load, or a lowvoltage dry-type transformer operated at 35%

clause 5.2.3 of Appendix S to this sk%W for licid; immersed transformers, and clause 5.3.3 for

dry-type transformers.

(2) Efficiency of a transforme perated continuously at 50% or 35% of rated output

power, as appropriate, tenmin in a ordance with clause 5.4 of Appendix S to this Subpart.

(3) The estimated V ual ergy consumption (EAEC), expressed in kilowatthours. per

year, for distribution tranperati ng continuously at 50% or 3 5%, of rated output power,

as appropriate, shall be the product of (i) the total transformer losses in kilowatts as determined

in (s)(2) above, and (ii) the representative use cycle of 8766 hours per year.

* * *

4. Section 420.23 is amended by adding new paragraph (s) as follows:

§ 420.23 Units to be tested.

* * * * *.

18

NIST DRAFT OF NOPR FOR DISTRlBUTION TRANSFOFJv.1ER TEST PROCEDURE 

**********"'*"'************"'*"'************************************************ 

amplitudes of the voltage and Current. 

'" '" '" '" '" 

3. Section 430.22 is amended by adding new paragraph(s) 

§ 430.22 Test procedures for measures of energy con 

'" '" '" * '" 

(s) Distribution, Transformers. (1) Total power losses; 

immersed or medium-voltage dry-:type trans 50% of the rated load, or a lowvoltage dry-type transformer operated at 35% load, determined in accordance with 

clause 5.2.3 of Appendix S to this s . -immersed transformers, and clause 5.3.3 for 

dry-type transformers. 

(2) Efficiency of a transform erated continuously at 50% or ~5% of rated output 

. power, as appropriate, ordance with-clause 5.4 of Appendix S to this Subpart . 

ergy consumption (BAEC), expressed in kilowatthours per 

year, for distribution transfo s operating continuously at 50% or 35%, of rated output power, 

, as appropriate, shall be the product of: (i) the total transformer l~sses in kilowatts as determined 

in (s)(2) above, and (ll) the representatiye use cycl~ of 8766 hours per year. 

'" '" '" '" '" 

4. Section 420.23 is am~nded by adding new paragraph (s) as follows: 

§ 420.23 Units to be tested •. 

'" '" '" '" '" 

18 
KIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE.

(s) (1) [Editorial note: first alternative considered]

For each basic model of distribution transformers , as defined in §430.2, a sample of

cient size sh be tested to insure that any represented value of transformer efficiency shall be

no greater that the lower of (A)'the mean of the sample 'or (B) the 95% confidence limit of the

estimated true mean divided by 0.999.

[Editorial note: second alternative considered]

A sample of no.fewer than five units shall be sel

efficiency of the sample shall be in compliance witli

to the basic model. The compliance sa demonstra

analysis.

Step 1. The first sample

Step 2. Compute th

sample as folio

random aid tested. The measured mean

mandated minimum efficiency applicable

by the following sampling plan and

be 5 or more units.

measured efficiency of the n, units in-the first

.Step 3 . Compute the sample standard deviation (S1) of the measured efficiency of the n,

units in the first sample as follows:

E&I(X; -X1)2

n1-1

19

• • '["' 

mST DRAFT OF' ~OPR FOR DISTRIBUTION l'RANSFORMER TEST PROCEDURE. 

****************************************~***********************************. . , ~. .' . /" . . 

(8) (1) [Editorial note: first ·alternative considered] 

For each basic model of distribution transfonners, as defined in §430.2, a sample of 

"sufficient size shall be tested to insure that any represented value oftransfonner efficiency shall be 

'no greater that the lower of (A )'the mean of the sample or (B) the 95% confidence limit ~fthe 

" '.' . . " / . " estimated-true mean divided by 0.999. ' 

[Editorial note: second alternative considered] 

, A sample of noiewer than five uints shall be sel 

efficiency of the sample shall be in cOmpliance witH 

to the basic model. 

analysis. 

St~p 1. 

The measured mean 

. dated minimum efficiency applicable I I \ ' 

by the following sampling plan and' . 

Step 2. meaSured efficiency of the n1 units in· the first 

·Step3.· 

e effiCiency of unit i. 

Compute the sample standard deviation (SI) of the measured efficienCy of the n1 

units in .the first ,sample as follow~: 

19 

, I 
,'MIST DRAFT OF NOPR FOR DISTRIBUTION. TRANSFORMER TEST PROCEDURE

Step 4. - Compute the standard error (SE(X)) of the mefficiency of the first sample as

follows:

Step 5. Compute the lower control limit (LCI,forie mean of the first sample using the

applicaple mandated efficiency (ME) as t desired mean as follows:

Here t is the 10th pe ile of a i tribution for a. sample size of ' n, and yields a

90 percent confi ce le or one-tailed t test.

Step 6. Compare the mean o e first sample (X1) with the lower control limit (LCL) to

determi one of foll ng.

If t mean f the first sample is below the lower control limit, then the

basic rnlffe! is in noncompliance and testing is at an end.

Step 7.

(ii) If the mean is equal to or greater than the lower control limit, no final

determination of compliance or noncompliance cap be made ; proceed to

Step 7.

Determine the recommended sample size (n) as follows:

n

1S1(106 - 0.06ME)

=

ME(6 0.06M&)

20

1

. .,' .. 

'~ 

.. \ 

'. 

", 

" 

, 'NIST DRAFT OF ,NOPR FOR DISTRIBUTION. TRANSFORMER TEST PROCEDURE 

********************************'*************************"'*************~.  

Step 4. 

Step 5. 

Step 6, 

Step i 

Compute the standard error (SE(X1» of the mean efficiency of the first sample as 

follows: 

'- S' SE(X)=_l " 1 . ,Ft: 

Compute the lower control limit (Le e mean of the first' sample using the 

, applicaple mandated efficiency (ME) ~ ,t 

(i) 

i tribution 'for a sample size of, n 1 "and yields a 

e first sample (XI) with the lower controllimit (LCL) to 

f the first sample is below the lower control limit, then the, 

el is in noncompliance and testing is at an end. 

'(ii), If the mean is equal to or greater than the lower cont'rollimit, no final 

determination of Compliance or noncompliance cap \>e made; proceed to 

Step 7. 

Determine the recomn:tended sample size (n) as follows: 

n ~.{tSl(106 ~ o.06ME)f ' 

'. ME(6,;, O.06ME) 

20. 

.-. 
FIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

Step 7.

Step 7. Determine the recommended sample size (n) as follows:

n=

tS,(106 - 0.06ME)

ME(6 - 0.06ME)

where S, and t have the values used in ste and 5, res ively. The factor

is based on a 6 percent toler the total 09ses. Oven the value of n,

determine one of the following'

(i) If the value o 's les nor equal to n, and if the mean efficiency of the first

sample (X) is equal t r greater than the lower control limit (LCL,) , the basic

model i comp ce d testing is at an end.

(ii) If the value n is greater than n,, the basic model is in noncompliance. The

size of a second sample n2 is determined to be the smallest integer equal to or

greater than the difference n - n,. If the value of n2 so calculated is greater than 20

- n,, set n2 equal to 20 - n,.

Step 8. Compute the combined mean (X2) of the efficiency of the n, and n2 units of the

combined first and second samples as follows:

21

· NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

** ************************************************************************** 

Step 7. 

Step 8. 

Step 7. 

Determine the recommended sample size (n) as follows: 

where S I and t have the values used in ste The factor 

is based on a 6 percent toler G~ven the value of n, 

(i) If the value 0 or equal to nt and if the mean efficiency of the first 

r greater than the lower control limit (LCL1) , the basic 

model i i:l testing is at an end. 

n is greater than nt, the basic model is in noncompliance. The 

size of a second sample n2 is determined to be the smallest integer equal to or 

greater than the difference n - nt. If the value of nz so calculated is greater than 20 

Compute the combi~ed mean ~)ofthe efficiency of the n1 and ~2 units of the 

combined first ~d second samples as follows: 

21 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

_ ni+n2

X2 Xin] + n2 i =1

Step 9. , Compute the standard error (SE(X2)) of the meanncy of the n1 and n2 units

in the combined first and second samples as fol

(Note that S1 is the value obt above in

Step 10. Set lower control limit (LCL2)

twined in Step 5 and compare the combined sample mean

onmol limit (LCL) to fine one of the following:

(i) If the mean of the combined sample (X2)is less than the lower control limit

(LCL2), the basic model is in noncompliance 'and testing is at an end.

(ii) If the mean of the combined sample (X2) is equal to or greater than the lower

control limit (LCLZ), the basic model is in compliance and testing is at an end.

(2) Selection of units to be tested-involving basic models having fewer than six units and basic

22

ft

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDuRE 

**************************************************************************** 

Step 9. 

Step 10. 

_ Compute the standard error (SE(X2» of the mean 

;-

in the combined first and second samples as fol 

(Note that Slis the value obt 

Set lower control limit (LC~) 

. ned in Step 5 and compare the combined sample mean 

oI,limit (LC~ to fine one of the following: 

(i) If the mean of the combined sample (.r2)is less than the lower control limit 

(LCLJ, the basic model is in noncompliance'and testing is at an end. 

(ii) If the mean of the combined sample (.X2) is equal to or greater than the lowercontrol.limit(LCL0, the basic model is in compliance and testing is at an end. , 

. (2) Selection of units to be tested involving basic models having fewer th~ six units and basic 

22 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

models for which all units are tested . (i) For those basic models of distribution transformers, as

defined in §430.2, for which fewer than six units have been produced over the preceding period of

180 calendar days, all transformers produced over that period shall be tested and any represented

value of transformer losses, transformer efficiency, annual energy n . mption, or other measure

of energy consumption for a basic model shall be the mean v o e tested transformers.

(ii) In lieu of using the sampling approach of § 43 (s)(1), all s of a basic model

produced during the preceding 180 calendar days ca e t ed and any represented value of

transformer losses, transformer efficiency, annual energy nsumption, or other measure of

energy consumption for a basic model shall mean val of the tested transformers.

5. Subpart B of Part 43( ame byyaading Appendix S consisting of sections 1, 2, 3,

4, and 5 as follows:

Appendix S to Subpart f Pa 430--Uniform Test Method for Measuring the Energy

Consumption of Distributio ransformers.

1. Definitions

1.1 ANSI Standard means a standard approved by a committee accredited by the

American National Standards Institute.

1.2 IEEE Standard means a standard developed and approved by the Institute of

23

IT

NlST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

**************************************************************************** 

models for which all units are tested. (i) For those basic models of distribution transformers, as 

defined in §430.2, for which fewer than six units have been produced over the preceding period of 

180 calendar days, all transformers produced over that period shall be tested and any represented 

value of transformer losses, transformer efficiency, annual energy mption, ,Or other measure 

of energy consumption for a basic model shall be the mean v 

(ii) In lieu of using the sampling· approach of § 43 s of a basic model 

produce~ during the preceding 180 calendar days ca d and any represented value of 

transformer losses, transformer efficiency, ~ual energy umption, or other measure of 

energy consumption for a basic model shall of the tested transformers. 

'" ... '" '" '" 

5. Subpart B of Part 43 a ding Appendix S consisting of sections I, 2, 3, 

4, and 5 as follows: 

Appendix S to Subpart 430-Uniform Test Method for Measuring the Energy 

Consumption of Distributio 

1. Definitions 

1.1· ANSI Standard means a standard approved by a committee accredited by the 

American National Standards Institute. 

1.1' IEEE Standard means a standard "developed and approved by the Institute of 

23 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

Electrical and Electronics Engineers. All IEEE standards referenced in Appendix S have been

approved or recognized by ANSI.

1.3 ISO Standard means a standard developed and approved by the International

Standards Organization.

1.4 NEMA Standard means a standard developed anipp ved by National Electrical '

Manufacturers Association.

1.5 Phase angle error means a measuremen rro introduced by phase angle

displacement between voltage and current phasors in the st equipment. Phase angle error, if

significant, can introduce errors in measured former los,

1.6 Phase angle correction.' means

negate the effects of phase angle err

(correction) of measurement data to

1.7 Reference teniperat me he J,einperature, specified in standards, to which the

transformer losses shall be corrected d reported.

1.8 Temperatu correc m s

Y

the adjustment (correction) of measurement data

obtained with the transfo r and test at a temperature that is different from the reference

temperature to values that wolffi have been obtained with the transformer at the reference

temperature. .

1.9 Test voltage, current, and frequency . mean voltage, current, and frequency of the

electric power supplied to the transformer under test.

2.0 Waveform correction means the adjustment (correction) of measurement data

obtained with a test voltage that is non-sinusoidal (distorted) to values that would have been

obtained with sinusoidal voltage.

24

11

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

*.* ••• **********~ •• *** •••••••• * •• **********.**.~.*.* ••• **.*.*.****.***.**~.* 

Electrical and Electronics Engineers. All IEEE standards referenced in Appendix S have been 

approved or recognized by ANSI. 

1.3 ISO Standard means a standard developed and approved by the Intemation81 

Standards Organization. 

1.4 NEMA Standard means a standard developed an 

Manufacturers Association. 

1.5 Phase angle error means a measuremen roduced by phase angle 

displacement between voltage and current phasors in the equipment. Phase angle error, if . 

significant, can introduce errors in measured 

1.6 Phase angle correction 'means th (correction) of m~asurement data to 

negate the effects of phase angle e 

1. 7 Reference temperat e emperature, specified in standards, to which the 

transformer losses shall be corrected 

s the adjustment (correction) of measurement data 

test at a temperature that is different from the reference 

temperature to values that wo. have been obtained with the transfornier at the reference 

temperature. 

. . . t 

1.9 Test voltage, current, andfrequency. mean voltage, current; and frequency of the 

electric power supplied to the transformer under test. 

2.0 Waveform correction means the adjustment (corre~tion) of measurement data 

obtained with a test voltage that is non-sinusoidal .( distorted) to values that would have been 

obtained with sinusoidal voltage, 

24 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

2. References.

2.1 ANSI Std. C57.12. 90-1993, "IEEE Standard Test Code for Liquid-Immersed

Distribution, Power, and Regulating Transformers and IEEE Guide for Short-Circuit Testing of

Distribution and Power Transformers."

2.2 ANSI Std. C57 . 12.00-1993, IEEE Standard Gen R 'rements for LiquidImmersed Distribution, Power, and Regulating Transfo

2.3 IEEE Std. C57.12.91-1995, IEEE Stand T Code for Dry-Type Distribution and

Power Transformers. • This Standard specifies test metho and certain test conditions for drytype distribution transformers.

2.4 ANSI Std. C57.12.01-1989, "IEE S eneral Requirements for Dry-Type

Distribution and Power Transforms luding use With Solid Cast and/or Resin -Encapsulated

Windings."

2.5 NEMA Standards Public 'on , TP 1-1996, "Guide for Determining Energy Efficiency

for Distribution Trans

2.6 ISO Standar 01-1 3, "Quality Systems-Model for quality assurance in design,

development, production, inst ation, and servicing."

2.7 Note: specific parts of standards C57.12 . 00-1993 , C57.12.01-1989, and C57.12.91-

1995 are designated in their original publications by the term "Section," similar parts in

standards C57.12. 90-1993 and ISO 9002 : 1987(E) are designated by the term "Clause ." The use

of these terms is retained in.this DOE test procedure.

record keeping of calibration data of test and measuring instruments.

25

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

**************************************************************************** 

2. References. 

2.1 ANSI Std. C57.12.90-1993, "IEEE Standard Test Code for Liquid-Immersed 

Distribution, Power, and Regulating Transformers and IEEE Guide for Short-Circuit Testing of 

Distribution and Power Transformers. " 

2.2 ANSI Std. C57.12.00-1993, IEEE Standard Gen 

Immersed Distribution, Powet:, and Regulating Transfo 

2.3 IEEE Std. C57.12.91-1995, IEEE Stand Code for Dry-Type Distribution and 

Power Transformers .. This Standard specifies test metho d certain test conditions for dry-

. type distribution transformers. 

eneral Requirements for Dry-Type 

Distribution and Power Transform.efal!ib\C. e With Solid Cast and/or Resin-Encapsulated 

Windings." 

. n, TP 1-1996, "Guide for Determining Energy Efficiency 

for Distribution Transft 

3, "Quality Systems-Model for quality assurance in design, 

development, production, inst ation, and servicing." 

2.7 Note: specific parts of standards C57.12.00-1993,·C57.12.01-1989, and C57.12.91-

1995 are designated in their original publications by the term "Section,'; similar parts in 

standards C57.12.90-1993 and ISO 9002: 1987(E) are designated by the term "Clause." The use 

of these terms is retained in this DOE test procedure. 

record keeping of calibration data of test and ~e!lsuring instruments. 

25 
.KIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

. 3. Test Conditions.

3.1 No-load losses, liquid-immersed transformers. The test conditions for measuring the

no-load losses shall be those specified in ANSI Std. 057.12.90-19 a test voltage and

frequency given in Clause 8.2.4; the waveform correction giv in use 8 .3; and the

temperature correction given in Clause 8.4. ANSI Std. A2.00=199 ecifes in Section 5.9

the reference temperature for reporting the measure

3.2 Load losses, liquid immersed tr rmers. Th est conditions for measuring load

losses shall be those specified in ANSI Std. C .1 3 and in ANSI Std. C57.12.00-1993.

ANSI Std. C57.12.90-1993 specifie therma gpditions of the transformer under test in

Clause 5.1 (includingJits Subcla ) Clause 9.3; the test frequency, the maximum value of

correction to the measured load. loss ue to the test system phase angle error, and the minimum

size of the conductors d for s rt-ci uiting the terminals in Clause 9 .3; the magnitude of.the

test current in Clause 9 .3 . ; the mperature correction to the measured load losses in Clause

9.4.2; and the phase angle co ion to the measured load losses in Clause 9.4.1. ANSI Std.

C57.12.00-1993 specifies the reference temperature for reporting the measured load losses at. the

rated load in Section 5.9.

3.2.1 For the purpose of this DOE test procedure the load losses of liquid-immersed

transformers shall be corrected to 50% of the rated, load value and the reference temperature of

55°C.

26

,NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE ' 

•••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 

3. Test Conditions. 

3.1 No-load losses, liquid-immersed transformers. The test conditions for measuring the 

no-load losses shall be those specified in ANSI Std. C57.12.90~19 . e test voltage and. 

frequency given in Clause 8.2.4; the waveform correction giv 

temperature correction given in Clause 8.4. ANSI Std. ecifies in Section 5.9 

the reference temperature for reporting the measure 

3.2 Load losses, liquid-immersed fr, Th est conditions for measuring load 

losses shall be those specified in ANSI Std. C 3 and in ANSI Std. C57.12.00-1993. 

ANSI Std. C57.l2.90-1993 specifi ditions of the transformer under test in 

Clause 5.1 (including"its Subcla . CI use 9.3; the test frequency, the maximum value of 

correc~ion to the measured load, loss ue to the test system phase angle error, and the minimum 

size of the conductors iting the terminals in Clause 9.3; the magnitude ofthe 

test current in Clause 9.3. mperature correction to the measured load losses in Clause 

9.4.2; and the phase angle co ion to the measured load losses in Clause 9.4.1. ANSI Std. 

C57. 12.00-1993 specifies the reference temperature for reporting'the measured'load losse~ at the 

rated loa,d in Section 5.9, 

! 3.2.1 For the purpose of this DOE test procedure the load 10sse~ pfliquid-immersed 

transformers shall be corrected to 50% of.the rated, load value and the reference temperature of 

26 
KIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

3.3 No-load losses, dry-type transformers. The test conditions for measuring no-load

losses of dry-type distribution transformers shall be those specified in ANSI Std. C57.12.91-1995:

the rated voltage and frequency are specified in Section 8.2.4; the A horm correction to

sinusoidal conditions is specified in Section 8.3.

3.3.1 In addition, during the measurement of -loll losses, the average temperature of

the core shall be measured or determined from ambient c ditions.

3.3.2 For the purpose of this DOE to pr e , the no-load losses shall be measured

at or corrected to the reference tem ure of

3.4 Load losses, dry- ans ers The test conditions for measuring the load losses

of dry-type distribution transformers all be those specified in ANSI Std. C57. 12.91-1995 and in

ANSI Std. 057.12.01- 9: St 057.12:91-1995 specifies the conditions for determining

the temperature of the wi ngs i ections 5.2 and 9.3; the size of conductors and precautions

for short-circuiting the wind' are given in Section 9. 3; and the test frequency is specified in

Section 9.3. ANSI Std. C57.12.01-1989 specifies in Section 5.9 that-the load losses shall be

based'on a reference temperature equal to the rated average winding temperature rise plus 20°C.

The rated average winding temperature rises for five insulation system temperatures are listed in

Table 4A of ANSI Std. C57.12.01-1989.

3.4.1 For the purpose of this DOE test procedure,.the load losses of dry-type

27

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

***************************.************************************************ 

3.3 No-load losses, dry-type transformers. The test conditions for measuring no-load 

losses of dry-type distribution transformers shall be those specified in ANSI Std. C57.12.91-1995: 

. _ the rated voltage and frequency are specified in Section 8.2.4; the 

sinusoidal conditions is specified in Section 8.3 .. 

3.3.1 In addition, during the measurement of losses, the average temperature of 

the core shall be measured or determined from ambient c 

3.3.2 For the purpose of this DOE te , the no~load losses shall be measured 

.' at or corrected to the reference tern 

. 3.4 Load losses, dry- he test conditions for measuring the load losses 

of dry-type distribution transformers I be those specified in ANSI Std. C57.12.91 .. 1995 and in 

ANSI Std. CS7.12.01- 57.12;91-1995 specifies ~he conditions for determining 

ections 5.2 and 9.3; the size of conductors and precautions 

for short-circuiting the wind' are given in Section 9.3; and the test frequency is specified in 

Section 9.3. ANSI Std. C57.12.01-1989 specifies'in Section 5.9 thatthe load losses shall be 

based'on a reference temperature equal to the rated average winding temperature rise plus 20°C. 

The rated average winding temperature rises for five insulation system temperatures are listed in 

Table 4A of ANSI Std. C57.l2.01-1989. 

3.4.1 For the purpose of this DOE test procedure, the load losses of dry-type 

27 
.KIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

transformers shall be corrected to 50% of the rated load for medium-voltage transformers, to

35% ofthe rated load for low-voltage transformers, and to the reference temperature of 75°C.

4. Test Methods and Instrumentation,

4.1 No-load losses, liquid-immersed transformer he test me d and instrumentation

shall be those specified in ANSI Std. 057.12.90-199 laie 8.2 and all its Subclauses.

4.2 Load losses, liquid-immersed tr rmers. Th est methods and instrumentation

shall be those specified in ANSI Std . C57.12. -1 use 9.3 and all its Subclauses.

Resistance and temperature measur ts, ge n for measurement of load losses, shall be

performed according to Clause , 5. d 5 3 (including all Subclauses) of ANSI Std:

C57.12.90-1993.

4.3 No-load lose e transformers. The test method and instrumentation shall be

those specified in ANSI Std. 12.91-1995, Sections 8.2.1, 8.2.2, and 8.2.3.

4.4 Load losses, dry-type transformers. The test method and instrumentation shalt be

those specified in ANSI Std. C57.12.91-1995, Sections 9.3.1, 9,3.2, and 9,3.3.4. Resistance and

temperature measurements, germane for the measurement of load losses , shall be performed

according to Sections 5.4 (including all Subsections) of ANSI Std. C57.12.91-1995.

28

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

**************************************************************************** 

transformers shall be corrected to 50% ofthe rated load for medium-voltage transformers, to 

35% of the rated load for low-voltage transformers, and to the reference temperature of 75°C. 

4. Test Methods and Instrumentation. 

4.1 No-Iocld losses, liquid-immersed transformer. a and instrumentation 

shall be those specified in ANSI Std. C57.l2.90-199 

4.2 Load losses, liquid-immersed tr est methods and instrumentation 

, shall be those specified in ANSI Std. C57.12. - use 9.3 and all its Subclauses. 

Resistance ,and temp·erature·measur for measurement oflQad losses, shall be 

performed according to Clause 5 3 (including all Subclauses) of ANSI Std. 

C57.12.90-1993. 

e transformers. The test method and instrumentation shall be 

those specified in ANSI Std. .12.91':'1995, Secti~ns 8.2.1,8.2.2, and 8.2.3. 

4.4 Load losses, dry-type transformers. The test method ~d instrumentation shall be 

those specified in ANSI Std. C57.12.91-1995, Sections 9.3.1, 9.3.2, arid 9,3.3.4. Resistance and 

temperature measurements, germane for the measurement of load losses, shall be performed 

according to Sections 5.4 (includIng all Subsec,tions) of ANSI Std. C57.12.91-199S. 

28 
NIST DRAFT OF NOPR FOR. DISTRIBUTION TRANSFORMER. TEST PROCEDURE

4.5 Accuracies required for measuring no-load and load losses of liquid -immersed and

dry-type distribution transformers shall be those specified in ANSI Std. C57.12.00-1993, Section

9.4.

4.6 Test equipment and measuring instruments shall ained and calibrated,

calibration records maintained to ensure compliance with previous c e 4.5 . Guidance of

general quality assurance procedures in testing is ava ' le ' the following cited Clause 4.11.1 of

ISO Standard 9001-1993, "Quality Systems-Model for ity assurance in design,

development, production, installation, and s

"The supplier shall establish and mat

and maintain inspection, in

ented procedures to control, calibrate

equipment (including test software) used by

the supplier to demons the armance of product to the specified requirements.

Inspection, measurin and to qulpment shall be used in a manner which ensures that

measurement u ertain kn n and is consistent with the required measurement

capability. "

5. Measurements and Calculations.

5.1 Measure the noload and load losses of a transformers according to test methods in

Clause 4 of this .Appendix.

5.2 Calculate the load losses of liquid-immersed transformers based on operation at 50%

29

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

**************************************************************************** 

4.5 Accuracies required for measuring no-load and load losses ofliquid-immersed and 

dry-type distribution transformers shall be those specified in ANSI Std. CS7.12.00-1993, Section 

9.4. 

4.6 Test equipment and measuring instruments shall 

. calibration records maintained to ensure compliance withe 4.5. Guidance of 

general quality assurance procedures in testing is ava' the following cited Clause 4.11.1 of 

ISO Standard 9001-1993, "Quality Systems-Model for 

development, production, installation, and s 

"The supplier shall establish and mai ented procedures to control, calibrate 

and maintain inspection, mequipment (including test software) used by 

the supplier to demons ance of product to the specified requirements. 

ipment shall be used in a manner which ensures that 

measurement u and is consistent with the required measurement 

capability. " 

5. Measurements and Calculations. 

5. J Measure the no-load and load losses of a transformers according to test methods in· 

Clause 4 of this Appendix. 

5.2 Calculate the load losses of liquid-immersed transformers based on operation at sq% 

29 
MST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

of the rated output power.

5.2.1 Correct the measured no-load loss data of liquid-immersed transformers to

sinewave basis according to-ANSI Std. C57.12.90-1993, Clause

5.2.2 Correct the measured load loss data of ersed t formers for phase

angle errors in measuring instruments, if significant, rd g to 'ANSI Std. 057.12.90-1993,

Clause 9.4.1.

5.2.3 Correct the no-load and load 1o v e Clauses 5.2.1 and 5.2.2 to reference

temperature of 20°C for no-load to rid 55 ° f r load Josses and add the two to obtain the

total losses based on operation 0% e r ted output power.

5.3 Calculate a load ses dry-type transformers based on operation at 50% or

35% of the rated output p ter, a ppropriate.

5.3.1 Correct the measured no-load loss data of dry-type transformers to a sinewave

basis according to ANSI Std. C57.12.91-1995, Section 8.3. .

5.3.2 Correct the measured load loss, data of dry-type transformers for phase angle errors

in measuring instruments, if significant, according to. ANSI Std. C57.12.90-1993, Clause 9.4.1.

30

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

**************************************************************************** 

of the rated output power. 

5.2.1 Correct t~e measured no-load loss data of liquid-immersed transfonners to 

sinewave basis according to, ANSI Std. C57.12.90-1993, Clause 

5.2.2 Correct the measur~ load loss data ofliq' . onners for phase 

angle errors in measuring instruments, if significant, 

Clause 9.4.1. 

5.2.3 Clauses 5.2.1 and 5.2.2 to reference 

temperature of 20°C for no-load 10 :6 r load losses and add the two to obtain the 

total losses' based on operation 

,5.3 Calculate dry-type transformers based on operation at 50% or 

5.3.1 Correct the measured no-load loss data of dry-type transformers to asinewave 

basis according to ANSI Std. C57.12.91-1995, Section 8.3. 

5.3.2 Correct the measured load loss, data of dry-type transfonner.s for phase angle errors 

in measuring instruments, if significant, according to ANSI Std. C57.12.90-1993, Clause 9.4: 1. 

30 
NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

5.3.3 Correct the no-load and load loss values of Clauses 5.3.1 and 5.3.2 to reference

temperature of 20°C for no-load losses and 75 'C for load losses. Add the temperature-corrected

no-load loss and load loss values to obtain the total losses based on operation at. 50% or 35% of

the rated output power, as appropriate.

5.4 Calculate the efficiency in percent of transf rs operatin 50% or 35% of the

rated output power, as appropriate by using the equ

E50(35) = 100 { P50(35) I (P50(35) + 5) )],

where ESO(35) is the efficiency of the transfo n percent en operated at 50% (35%) of the

rated output power, P50(35) is the output powe 0% or 35 % of the rated (nameplate).

value, and £50(35) is the total loss po f the tr s rmer in kW at 50% or 35. % of the rated

output power.

31

. NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

******************************~********************************************* 

5.3.3 Correct the no-load and load loss values of Clauses 5.3.1 and 5.3.2 to reference 

temperature of 20°C for no-load losses and 75 °C for load losses. Add the temperature-corrected 

no-load loss and load loss values to obtain the total J~sses based on operation a~· 50% or 35% of 

the rated output power, as appropriate. 

5.4 Calculate the efficiency in percent oftransfi 50% or 350/0 of the 

rated output power, as appropriate by using the equ 

ESO(3S) = 100 [ P 50(35) I ( P 50(35) 

where ES0(3s) is the efficiency of the transfo 

rated output power, P 50(35) is, the output powe 

value, and 150(35) is the total loss po 

output power. 

31. 

n operated at 50% (35%) of the 

. 0% or 35 % of the rated (nameplate) 

nner in kW at 50% or 35 % of the rated 
KIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

Table 1

Preferred Standard kVA Ratin

Liquid-Immersed Distribution Try

667

833

1000

1500

2000

2500

s

32

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFOR1vfER TEST PROCEDURE 

•••••••••••••••• ** •• **.**.*** •• * ••• *, ••••••••••••• **** •••• * ••• ** •••••••••••• 

Table 1 

Preferred Standard kV A Ratin 

Liquid-Immersed Distribution Tr 

Single-Phase 

Power Rating, 

kVA 

10 

15 

25 

37.5 

50 

'75 

100 

167 

250 

333 

500 

667 

833 

150 

225 

300 

500 

750 

1000 

1500 

2000 

2500 

32 
MST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE

Table 2

Preferred Standard kVA Rating

Dry-Type Distribution Transform

Low Medium

Voltage, Voltage,

s 1.2 kV > 1.2 kV

33

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

* •••••• * •• * •••• * ••• ~ •• *** •• *.*****.**********.***** ••••• ******.*****.******. 

Power 

Rating, 

kVA 

15 

.25 

37.5 

50. 

75 

·100. 

167 

250 

333 

50.0 

667 

833 

Table 2 

Preferred Standard kV A Rating 

Dry-Type Distribution Transfo 

Single-Phase 

Low 

Voltage, 

~ 1.2 kV 

112.5 

150. 

225 

30.0. 

500 

750. 

100.0. 

1500 

20.0.0. 

250.0. 

33 

Low 

Voltage, 

s: 1.2 kV 

Medium 

Voltage, 

> 1.2 kV 
KIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFO R TEST PROCEDURE

Table 1-A

°C

Reference

Temperature

°C . 1 °C °C

Liquid-Immersed

85 1 65.

130 60

150 80

185 115

200 130

220 150'

85

80

100

135

150

170

35

30

.40

60

65

75

Assumptions:

No-load losses 25%; load losses 75%

Algorithm : aT=kW

AT - - temperature rise

W - - dissipated power

k - - constant

AT rounded off to the nearest 5°C

Calculated Temperature Rises for Transformers Operated at Lower Than The Rated (Nameplate) Load

Insulation

System

Temperature

Rating

Temperature Rise at

Rated Load

Temperature Rise at

50% of Rated Load

Estm. Reference

Temperature at 50'%

of Rated Load

°C

50

60

25

35

80 50

85 55

95 65

Temperature Rise at

35% ofRatedLoad

Estm. Reference

Temperature at 35%

of Rated Load

°C

45

55

70

75

85

.34

NIST DRAFT OF NOPR FOR DISTRIBUTION TRANSFORMER TEST PROCEDURE 

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Table I-A 

Calculated Temperature Rises for Transformers Operated at Lower Than The Rated (Nameplate) Load 

Insulation Temperature Rise at 

System Rated Load 

Temperature 

Rating °C 

°C 

85 65 

130 60 

150 80 

185 115 

200 130 

220 150 . 

Reference Temperature Rise at Estm. Reference 

Temperature SO"..4 of Rated Load Temperature at SO"..4 

of Rated Load 

°C °C °C 

.-

Liquid-Immersed 

85 35 55 

Dry-Type 

80 30 50 

100 .40 60 

135 60 80 

150 65 85 

170 75 95 

Assumptions: 

No-load losses 2S%; load losses 7S% 

AJgoritlnn: AT=k~~ 

AT- .. temperature rise 

W .... dissipated power 

k .... constant 

AT rounded off to the nearest SoC 

.34 

Temperature Rise at Estm. Reference 

3S% ofRated,Load Temperature at 3S% 

ofRsted LOad' 

°C °C 

-- --

25 45 

35 55 

50 70 

55 75 . 

65 85