To: D Distri b Ener g

Subj e Dear
This a Stak e accu r docu m be us webs i
1 2 3 4 5

A D OE Stakeho b ution Trans fo g y Efficiency D

e ct: DOE Dis t

Stakeholder:

a nalysis of Di s e holders who r ate analysis a m ents. It is m y eful. I will p o i te for all inte r
. Introducti o . Referenc e . Analysis . Conclusio n . Recomme
A

. Introdu c In 2007, I w to addres s Departme n Avery lar g Meetings. manufact u analyzed a IEEE Tran Transform Proposals

. I am not a findings in energy eff i Regardles any of the the team.
I have ex a recognize applicatio n reasonabl e Standards lders for o rmer D eterminatio n

t ribution Tra n

s tribution Tr a have reques t a nd recomm e ysuspect th a o st a word ve r r ested partie s

o n e s

n s ndations

c tion

w as elected t s Stakeholde r n t Of Energy g e task force This task fo r u rers, users a a nd reported a sformers Co m ers Subcom m

. stakeholder b this report a r i ciencies for M s of the effici e stakeholder s

a mined distrib

the difficulty o n s. However, e selection fo

. n

sformer Loa d

a nsformer Lo a t ed that I pro v e ndations ba s a t a multiplicit y r sion on my I E s to access. T

o be Chairm a r s’ concerns a (DOE) regul a now meets r e r ce now has a nd other inte r a t each meet m mittee’s sit e m ittee, Task F

b ut will gladl y r e understoo d M edium Volt a e ncy levels t h s , this attemp t

ution transfo r o f finding a o n several type r use in setti n d ing Study

a ding was pr o v ide insight. M s ed on my pe yof stakehol d E EE Transfo r T he following

a n of an IEE E a nd issues wi t a tions for Dist e gularly at ea c a bout 100 m e r ested partie s ing with min u e at www.tran F orce for Rev

yparticipate w d by those w h a ge and Low V h at are select e tto display fa c

r mer loading f n e shoe fits a s of informati n g Distributio n 3704 Char Octo b Ph Fx Cell phop www

o mpted by th e M y objective rsonal experi d ers may fin d r mers Commi

topics will b e

E Transforme r t h current an d t ribution Tran s ch of the IEE e mbers and i s s . Data is re g u tes and pres e

sformersco m iew of DOE E

w here neede d h o will be sel e V oltage Distr i ed and of an y ctual informa

f rom 1992 th r a ll approach f o

on have bee n n Transform e High Ridge R lotte, NC 28 2 b er 9, 2011 704-846- 3 704-845- 2 704-236- 3 p kinson@hvol

.hvolt.com

e interest of a is to provide ence and ot h d this analysi s

ttee DOE En e e addressed:

r s Committe e d proposed c h s former Ene r E Transform e s composed o g ularly accum e ntations po s m mittee.org , D E nergy Effici e

d to be sure t h e cting the ne x i bution Trans f ypredispose d tion should p

r ough presen o r all transfo r n available to e r Energy Effi c R d 2 70
3 290 2 520 3 320 t.com

a number of

unfiltered h er backgrou n s and report t o e rgy Efficien c

e Task Force h anges to th e r gy Efficiency e rs Committe o f

ulated, s ted on the D istribution e ncy

h at the x t round of f ormers. d positions o f rove useful t o

t and r mer make a c iency



### 1 n d o c y

e

. e

f o

### 2 B. References: 1. FERC Form 1 Data 2. Electric Utility Total Owning Cost history 3. NEMA TP-1 from 2002 and from 1996 4. Distribution Transformer Size Optimizati on by Forecasting Customer Load by Jerrod Luze, Black Hills Power, Rapid City, South Dakota. 5. DOE Chapter 6 Energy Use and End Use Load Characterization. 6. ABB Total Ownership Cost (TOC) Calculator 7. Loading Study of a Manufacturing Plant by Philip J Hopkinson, PE (1995 and 2005) 8. Boston NEMA TP-1 Background (1995) 9. Optimizing Energy Efficiency Standards for Low Voltage Distribution Transformers a thesis by Ken Harden of Schneider Electric at Purdue University 10. NEETRAC Distribution Transformer Ther mal Test Procedure from May 29, 2002 11. My experience as a distribution tran sformer design engineer from 1966-2011 C. Scope 1. Medium Voltage Liquid Filled Distribution Transformers 2. Medium Voltage Dry Type Distribution Transformers 3. Low Voltage Dry Type Transformers. D. Assumptions 1. Transformers always remain energized and core loss (no load loss) is always occurring. 2. Transformer winding losses along with stra ys and eddies vary with the square of load current. 3. Historical no load and load loss relationships may be a significant indication for future decisions. 4. For all load considerations, peak transfor mer efficiency always occurs at the point where no load losses equal load losses. 5. Highest transformer losses occur at the highest permissible load. Hence differences in alternative transformer efficiencies at the highest load have greater impact on total watt losses. 6. Electric Utility Total Owning Cost (A and B factors) is representative of both the value of a watt saved and of their loading models. 7. Load cycles vary by regions of the countr y, by seasons of the year and by time of day. 8. RMS equivalent load is most representative of the watt losses that are being dissipated in the transformer in service. 9. Routine tests at a manufacturer’s produc tion facility should be converted to expected RMS equivalent load to verify the efficiency t hat will be most representative of the inservice condition. 10. The DOE measurement point for effici ency will normally o ccur at the most representative RMS equivalent load, which may or may not be equal to the point of peak efficiency where core loss equals load loss. However the transformer is usually most optimally designed for lowest cost wh en the measurement point occurs at the point of peak efficiency. E. A look at the 25 kVA single phase pole type transformer 1. The 25 kVA pole type transformer has been the most representative kVA rating for pole type transformers for many decades of time.

### 3 2. Many of the relationships for the 25 kVA transformer apply broadly to other medium voltage transformers, such as Total Owning Cost relationships and loss ratios. 3. During the 1960’s the 25 kVA transformer normally had 100 watts of core loss and 300 watts of load loss. 4. During the 1970’s Total Owning Cost relati onships were introduced with two factors, called A and B. The A factor was the present worth of a watt saved and was measured in $ / watt. The B factor was app lied to adjust full load winding loss to the value of load loss that is most representative of the normal expected operating condition, or the RMS equivalent load in se rvice. Mathematically, the following is a good way to visualize B: B= (PU Load)^2 * A (1) Where PU load is the per unit load of the transformer. Here, if PU Load is 0.5 then B becomes: B at 0.5 load = 0.5^2 * A = 0.25 * A (2) 5. In practice, the B factor is usually sli ghtly greater than the square of per unit load times A to recognize the value associated with peak demand. By increasing B slightly, the transformer will have suffici ently low load losses as to maintain a relatively flat efficiency over wide changes in load. This is im portant because loading can vary significantly and even exceed trans former rated kVA. If the transformer efficiency deteriorates excessively at high load then the peak demand may result in higher net cost to serve the load. 6. Total Owning cost formulas initially focu sed on an A factor of $3/watt and a B factor of $1/watt and remained in that range fr om the 1970’s to the mid 1980’s. 7. During the 1980’s and 1990’s wide variations of loss evaluations occurred with A factors varying from a low of under a dollar to as high as $10/watt. Interestingly the B factors remained mostly in a range of 0.2-0.3 * A. 8. In 1996, NEMA introduced TP-1, but derived from the relationship of a B factor = 0.25 A. Many manufacturers were solicited to supply design data that became the basis for the published efficiencies. 9. In 2007, the DOE published new mandatory efficiency values that became effective in 2010 that assumed an RMS equivalent load of 50% of nameplate. Manufacturers report that the same efficiencies may be reached by using TOC methods with an A factor of $4/watt and a B factor of $1/watt. 10. In 2011, many Utilities purchase transfor mers that just meet the DOE published efficiencies however some Utilities purchase tr ansformers to a TOC owning cost formula that reaches beyond the DOE requirements. The most common TOC formula for premium efficiencies is: a. A = $5.91/watt b. B = $1.81/watt 11. For any TOC relationship the RMS equivalent load is simply: RMS equivalent load = (B/A)^0.5 (3)
12. Recall that in the 1960’s the 25 kVA no load watts were 100 and the load watts were 300. Hence the assumed per unit load was: PU load in the 1960’s = (100/300)^0.5 = 0.58 (4) 13. From the 1970’s to the mid 1980’s t he assumed per unit load remained unchanged 14. During the 1980’s to 2000, some owning cost formulas had a B that was 0.25 A hence: PU load in the 2000-2011 period has ranged from 0.5-0.58 for all popular owning cost formulas.F

. Other L o 1. The F E total k i relatio name p as se a load d it is in losse s 50% o 2. Phil H o power transf o groun d harm o 3. Typic a

N M H w t h e h
4. A Lo o o ading relati o

E RC 1 report i lowatt-hours nship the si m p late. Howe v a sonal period s o es not mea s its normal se s that are pre s o f nameplate. o pkinson ma d to a manufa c o rmers were m d ed wye con n o nics and ma k a l load cycles

N ote that load M ississippi P o H owever, for 5 w here the sp e h at occurs, a n xpenditures b ighest loadin g

. o k at Low V o l o nships

shows total i of sales of el m ple average l v er, this inclu d s where load i s ure the loss e rvice. RMS e s ent over lon g d e a study of c turing plant. m easured as n ected transf o k ing a path fo

are as show n

ing can be q u o wer and Flor 5 0% RMS eq u cific individu a n y peaks in l o b y the Utility t g periods.
l tage Transf o nstalled cap a ectricity thro u l oad would a p d es many tim e i ng may be e i e s that are b e e quivalent lo a g periods. T h
the loads on The RMS e q 50% of nam e o rmers do a w r zero seque n n below:

u ite variable a i da Power ca u ivalent load, a l loads are n o ading may r e t o account fo r

o rmers a city of distri b u ghout the U n p pear to be a e s of light lo a i ther light or h e ing dissipate d a d is a true m h e RMS equi v

typical indus t q uivalent loa d e plate. Ther e w onderful job n ce currents.

a s a function o ses or flatter

, each profile ormalized. I n e sult in additi o rgeneration r b ution transfo r n ited States. little more th a d such as at h eavy. The s d by the tran s easure of th e v alent load is trial transfor m d to the liquid e he also lea r

of absorbing

o f time of da y as in the co m is replaced b n spite of the o nal peak de m r equirements r mers and From this an 20% of night as well imple averag s former whe n e transformer

closer to the

m ers supplyin

filled r ned that delt a third

yas in the m posite curve b y a flat curve

smoothing m and during the



### 4 e n

g

a :

.1. M e R M 3 5 2. M e 3 0 R M m o 3. T h 1 9 ty p 1 8 n o

Figure 1 s h Note that t impact on transform e load woul d e asurements M S equivale n 5 % of namepl e asurements 0 0 low voltag e M S equivale n o re than 35 % h e Cadmus G 9 90’s that su g p e transform e 8 % of namepl o t clear for th e a. When R efficie n by no l o b. When R efficie n load lo s efficie n result o load p e c. Figure efficie n 35% to optimi z

h ows total ef f t he efficiency watts loss in e r achieved p e d be strikingl y at the DOE F n t loading for L

ate. during the s u e dry transfor m n t. However r % which in tot a G roup and No r g gested loadi n e rs in some N ate. It may b e following re a R MS equival e n cy peaks at 3 o ad losses is R MS equival e n cy peaks at 1 s ses is 42. H n cy falls off v e o f this is that s e riods and le a

1 below, cou r n cy plots for 3

40% of nam e z ed for 30% a

f iciency vers u

of the three t the transfor m e ak efficienc y ylarge. F orrestal buil d L ow Voltage

u mmer mont h m ers sugges t r epeated me a a l was close t o rtheast Utiliti e n g of less tha N ortheast loc a

e true in so m a sons: e nt load is le s 3 5% of load, t

approximate e nt load is as 1 8% load the n H owever the c e ry quickly fo r s uch transfor m a d to the nee d rtesy of Ken H conditions o f e plate. Note re considera b

u s percent lo a t ransformers m ers is drama yat only 18% d ing in the e a Dry Type tra n h s at a manu f t ed that loadi n a surements i n o the 35% a s e s conducted n 35% of na m a tions and fo u m e locations b

s s than 35% o t he ratio of tr a ly 10. low as 18% o n the ratio of c onsequence rany conditio m ers may be d for greater t H arden of Sc fpeak efficie n that at high l o b ly less effici e

a d courtesy o f

is quite differ e tically differe n % of nameplat e a rly 1990’s co n sformers w a f acturing plan ng could be l e n the winter m s sumption for

loading stud i m eplate for lo u nd loading t o b ut the conse q

o f nameplate a nsformer lo a

o f nameplate load losses d of such a rat ns of high lo a less efficien t t otal delivere d hneider Elec t n cy, ranging f o ad the tran s e nt:

fKen Harde n ent at high lo n t at high loa d e kVA the fal l ncluded that a s close to

t of loads on e ss than 35 % m onths was

the year. i es in the lat e w voltage dry o be as low a s q uences are and the a d loss divide d and if d ivided by no

io is that a ding. The tduring high d load. t ric shows th e f rom 30% to s formers

n of Schneide r

ads. The d s. If a l off at high



### 5 %

e y s

d

e

r

.G

H

Philip Presi d Figure 2 s h Ken Hard e seasons.
G . Conclus i
1. Histo load s earli e 2. Histo load s starti n 3. Insta n need s 4. Peak for a t dem a H . Recom m 1. The D betw e depa r of 50 % 2. Low V Schn infor m close J Hopkinso n d ent & CEO H h ows a clear e n. Note the c This is the n a
i ons: rical purchas e s of 50-58% o e r forward to t

rical purchas e s of more tha n n g with the in n taneous loa d s daily and s e Demand ne e t ransformer s a nds on the l o

m endations:
D OE Negotia t e en no load a rture from hi s % RMS equi v V oltage loadi n eider Electri c m ation and a n ly for rational , PE H VOLT Inc. view of load v c lear differen a ture of much

e s of mediu m f nameplate R t oday. e s of low volt n 40% of na m troduction of d s are not a g e asonal effec t e ds to be con s uch that the h o ad supply.

t ing team sh o a nd load loss e s torical relatio v alent load h a n g informatio n chas done a c n y departure f

. v ariation at a ces in seaso n of the loadin

m Voltage tra n

R MS Equival e

a ge dry tran s m eplate prior t

NEMA TP-1 g ood indicati o t s to provide s idered in th e h ighest perm

o uld work clo s e s for Mediu m nships shoul d a s been in pl a n is not gene r c ommendabl e f rom the 35 % plant in Ten n n al loads by m n g on low volt a

n sformers ha v e nt load in s e

s formers hav e t o the mid 19 9 in 1996. o n of RMS eq adequate inf o e establishm e issible loads

s ely with EEI m Voltage Uti l d be carefull y a ce since at l e rally availabl e e job of exa m % load assum p n essee, agai n m ore than 2: 1 a ge dry type

v e been bas e e rvice from th e

e been based 9 0’s and 35 %
uivalent load o rmation. e nt of load lo s do not produ c

for the prope l ity transform e ystudied. Th e e ast back to t e but Ken Ha r m ining consid e

p tion should b n courtesy of 1 between transformers

e d on expect e

e 1960’s or on expected % of nameplat e

ing which

s s allowance c e excessive

r loss ratio e rs. Any e assumptio n t he 1960’s. r den of e rable b e examined



### 6 .

e d

e

n