DISTRIBUTION TRANS JRMER TECHNOLOGY

BEN MCCONNELL ENERGY DIVISION OAK RIDGE NATION : LABORATORY

JUNE 1 3 . 1994AMENTAL TRANSFORMER OPERATION

DEFINITION: TWO OR MORE COILS COUPLED BY A MUTUAL MAGNETIC FIELD. VARYING ALTERNATING VOLTAGE SOURCE IMPLIES VARYING FLUX

----- Vl*N1=V,*N ITI =IfI^T2_ VOLTAGE TRANSFORMATION DEPENDS ONLY ON THE EXISTENCE OF ALTERNATING FLUX. AIR CORE POSSIBLE BUT " ONE' CORE PREFERRED FOR EFFICIENCY.ORNL-DWG 94-1755

SOURCE

LOAD [ I ] v2

i m.. 11 0/2

0/2; P I MARY WINDING

(RolptAnnp = r, )

0/2 N 1 TURNS

N1TlIRN.

SECONDARY WINDING (Resistance = r2) 4

LAMINATED IRON CORECONNECTIONS IN T RZE DISTRIBUTION SYSTEMS

Fig 5 Single - ---:. w;-a-*`3rmer

Fig 7 3-Phase S-Legged Core ANSI/IEEE 067.105.1978

1 6 2L -Type Tvandormer

# Construction 

# O ,r y fOr Cas 

## + I?e skVWER EQUATION

VA = 4.443*f*N*J*AArw-*B..... *Aclw (MIKS UNTfS where, VA = RATED 1-PHASE POWER IN VOLT-i E S f = RATED FREQUENCY IN Hz N = NUMBER OF TURNS IN WINDING COBS FRED J = rms CURRENT DENSITY IN A SINGLE TTU`RN (Amps/MZ) Acrw = CRO S S- SE CTI ONAL AREA / TURN (M=Brow, = MAXIMUM FLUX DENSITY IN TESAclw = ACTIVE CORE CROSS-SECTIONAL AR.=A M2)VOLTAGE (MACHI' EQUATION

E (Volts) = 4.443*f*N*Bmax*Aclw, or VOLTSEJRN Volts/T = E/N = 4.443*f*B*Aclw or

MAXIMUM FL

UX DENSITY (4.443*f*Aclw)NO LO SSES (NLL)

NO LOAD LOSSES OR CORIE LOSSES ARE BASICALLY THE RESULT OF HYSTERESIS AND EDDY CURRENT LOSSES IN THE CORE MATERIALS AND ARE INDEPENDENT OF LOAD. NLL = P h + Pe = VOLCO (f* Kh *BXmax + Ke*f *t2*B2 where, Kh, Ke, x ARE CONSTANTS AND t = LAMINATION T.H C KNESS TYPICALLY 3-9 MIL FOR COLD ROLLED GRAIN OFIENTTED HIGH SILICON ( 3.5%) STEEIS (SiFe ) AND B IS 1.6-.8 TESLA. FOR AMORPHOUS T_ Ph =0 AND t = 1 MIL AND NLL ARE VERY LOW; BUT Bm= IS 1.4 TESLA. CORE PACKING FRACTION: = 0.95 FOR SiFe AND 0. FOR AMORPHOUS METAL NET COST OF AMORPHOUS CORE TRANSFORMER ABOUT 257o HIGHER.ORNL-DWG 94-1757

UtLMAUUNL I VA I ION

CURVE INITIAL MAGNETIZATION CURVE

HmOI NL= L)WO 94,17 66 2.0 1.8 1.6 p ap 1.4 1.2 z w 0 >G 1.0

0 0.6 0.4
0.2

0 2,500 5,000 7 ,500 10,000 MAGNETIC FIELD INTENSITY [H(A/m)] 12,5002.0 97 +--- 

### a Ell;

R o riented sheers'

: ' w. M9 t

5

IF J-1. -LI 1. 1 Irk Iiii -T

4 #

Exunple A-6

0.5 i

Example A-545 I I I I I i I I I I 8 10 11- 14 16

Magnetic Faux Densi-, n A,,,auss q Grain Oriented SiFe - amorphous Metal500 450 400 350 w 300 cf) 0250 J 200 0 H 150 100 50 0 ORNL-DWG 94-1765

0.16 0 .32 0.48 0.64 0.8 0.96 1.12 PER UNIT LOAD (Nameplate Rating = 1.0)TRANSFORMER =` CIENCY

MAXIMUM EFFICIENCY OCCL AT THE LOAD, S, FOR CH NLL = (S/Sb)2*LL AND E GIVEN BY EFFICIENCY(Eta) = POWERnut POWEROut + TL) or at uni: power factor, Et-z = S / (S + NLL + (S/Sb)2*LL ? where S = LOAD IN kVA, and NAMEPLATE RATING IN WVORNL-DWG 94-1764 99.5 99.4 PP11 99.2 99.1 99.0 98.9 98.8 98.7 98.6 98.5 98.4 98.3 98,2 98.1 003.0 97.9 97.8 97.7 97.6 97.5 MOD NLL, LOW LL 

### .t,

0.08 0
. 24 0.4 0.56 0.72 0.88 1.04 1.2

PER UNIT LOAD (Nameplate Rating = 1.0)TO DECREASE NO LOAID LOSSES

or

or CHANGE CORE MATERIALS REDUCE FLUX DENSITY (B) BY INCREASING CORE X -SECTION (Aclw) or DECREASING VOLTSITURN (EIN) REDUCE CORE FLUX PATH LE ` GT}I BY DECREASING CONDUCTORS X-SECTION (Acrw) FREE PARAMETERS : MATERIAL A lw, E/N, Acrw, HEIGHTS OF CORE AND COIL WINDOWS.or, DECREASE LOAD LOSSES

CHANGE CONDUCTOR MATERIALS REDUCE CONDUCTOR CURRENT DENSITY ( by INCREASE' : G CONDUCTOR X-SECTION (. is or REDUCE CONDUCTOR LENGTH by

REDUCING CORE X-SECTION (Acrw) or INCREASE VOLTS PER TURN (E/N), o 1: ^ -/Cd, tf:J e^ v N cv A A r& ° V 4.17 o o ° o° o° 0 0 oTRANSFORMER LIFE

A DESIGN LIFETRlE OF 20 YEARS IS TYPICAL ASSUMING FULL TIME OPERATION AT THE NAMEPLATE. TIllS DESIGN LIFETIME IS RELATED TO INSULATION LIF E WHICH DEPENDS ON THE HISTORY OF THE OPERATING HOT SPOT TEMPERATURE. PRESENT PRACTICE IS TO DESIGN FOR A HOT SOT TEMPERATURE RISE OF 65 DEGREES CELSIUS ABOVE AMBIENT IN OIL PAPER INSULATIONS AND 150 DEGREES CELSIUS IN DRY TYPE INSULATIONS. EXCEEDING THIS LIMIT FOR ANY SIGNIFICANT TIME QUICKLY R ED U CES EXPECTED TRANSFORMER LIFE WHILE BEING BELOW IT GREATLY EXTE ND S THE LIFETIME. NOMINALLY 5 0 % REDUCTION IN LIFE FOR EACH 8 DEG RE E RISE OTHER FACTORS INFLUENCE USEABLE LIFETTh E, SUCH AS LIGHTNING, ACCIDENT, AND EARLY RETIREMENT DECISIONS.UJ

360 2'S 0 220 180 40 120 100 80

HOTTEST SPOT TEMPEUTURE $ IIEGREES C_oss of life after one day's operation v7 fW load as a function of ambient te--^peaturef

Op erat ing time against hot spot temperature for on: y loss of life

4OVERLOAD ABILITY

OVERLOAD IS RELATED T ALLOWED TEMPERATURE RISE AND HEAT REMOVAL RATE. TYPICALLY OIL PAPER SYSTEMS CAN OPERATE AT UP TO 200% LOAD FOR PERIODS OF HOURS WITH JUT SIGNIFICANT LOSS OF PERFORMANCE BUT WITH LOSS OF TRANSFORMER LIFE. WHILE DRY TYPE INSULATION MATERIALS ARE CAPAB LE OF OPERATING AT HIGHS TEMPERATURE, THESE L NSULATION SYSTEMS AR SS TOLERANT OF OVERLOAD BECAUSE OF D HEAT REMOVAL CAPABILITY.SUMMARY

CLEARLY TRAIN N FORMER DESIGN IS AN I-- ERATIVE PROCESS AND T- HE CHOICE OF OPTDIIZA-ION VARIABLE CAN BE KEY. TI- 'ERFORMANCE OF THE INSULATING SYSTEM, THE V4 EIGHT AND EXTERNAL D I SIGNS MUST BE INCLUDED r,-- THE ANALYSIS. AT PRESENT TIT: TRANSFORMERS ARE I ESIGNED FOR THERMAL LIMITS AND PERHAPS TOTAL C -ING COSTS AND NOT FOR .f IMUM EFFICIENCY, M UM EFFICIENCY OVER SOME RELATIVE LOAD= RANGE OR MINIMUM LOSSES. THE DIFFERENCE IN TTTLITY AND INDUSTRLAL LOADING AND ECONOMIC PRACTICES WILL PLAY KEY ROLES IN ANY ANALYSIS. SINCE COST IS N RY STRONGLY RELATED TO MATERIALS QUANTITIES AND PERFORMANCE AND REDUCED LOSSES REQUIRE MORE AND/OR BETTER (MORE EXPENSIVE) MATERIALS, RE)U CED LOSSES AND INCREASED EFFICIENCY Mt ST BE CLOSELY EXAMINED RELATIVE TO INCREASED COTS..