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Reduction of Losses in Distribution Transformers
Dr. Juan C. Olivares-Galvan, ProfessorUniversidad Autonoma Metropolitana
Invited lecture for IEEE Greece PES Chapter4 November 2010, Athens, Greece
ContentI. IntroductionII. Stray losses in distribution
transformeresIII. Dielectric lossesIV. Tank losses due to high currents of LVV. Design parameters of wound coresVI. Conclusions
I. IntroductionOverheatingInsulation designLoss reductionNoiseSize and shape
No-load testLoad test
Objetive Reduce transformer losses
Pno-load = Pe+Ph+ Pd
Pload= PI2R+PEC+Pstray
Why distribution transformers?
5000-MW utility system
With reduction of losses Mexico will invest less in generation
0.0
50.0
100.0
150.0
200.0
250.0
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 Año
GWh
Producción Producción
Demanda Demanda
0.0
50.0
100.0
150.0
200.0
250.0
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 year
G Wh
Installed generation
Demand
II. Stray losses in transformers
500 kVA, shell typeClosed topologyEddy current cancelationLoad test
Stray losses vs transformer rating
7359.4)(9838.0)(0007.0 2 −+= kVAkVAPstray2056.0
/ )(0393.0 kVAP LS =W
Description of experiment
Results of experiments
roµµσωδ 2=
Incident, reflected and transmitted fields near the surface of conductors
Js
σ large
Depth of penetration
Incident H field
Reflected H-field
Transmitted H- field
Present worth analysis
( ) Aii
iP n
n
)1(11
+−+
=
Cost ofelectromagnetic shield= 10%
i =10 percent
0 30 US$18
P
Transformer life
Time
02468
10
Loss
cos
t as
a pe
rcen
tage
of
tran
sfor
mer
cos
t
Time (years)
IV. Dielectric losses
P2>P3, P2>P1
CVPd δω tan2=
Stages of transformer manufacturing
IV. Tank losses due to high currents of LV
Pad-mounted transformersWith and without stainless-steel plateIX= 590.49 A, IH=5.65 APlate thickness: 6.35 mmAISI 304Carbon steel: ASTM A36
Experimental results
A=B=36 cm=15δ
Test with and without stainless steel Same active element was usedTests without oil
Load lossses vs primary current for a 225 kVA transformer
Simulations
Simulations in 3D of tank losses
Nodes: 12179Elements: 90179
Magnetic field measurements around LV
0
10
20
30
40
50
60
70
80
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Points
Peak
mag
netic
flux
den
sity
(m
illig
auss
)
112.5 kVA150 kVA500 kVA
fE
Gauss mvpeakpeak ⋅
⋅=
2.1560 ,
Magnetic field measurements
1 2 3
4 5 6
7 8 9
10 12
13 14
11
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Points
Peak
mag
netic
flux
den
sity
(m
illig
auss
)
Maximum values of electric field and magnetic flux density in public areas
ICNIRP: International Comission on Non-Ionizing Radiation ProtectionCENELEC: Comité Européen de Normalisation ElectrotechniqueIRPA: International Radiation Protection AssociationNRPB-UK: UK National Radiation Protection Board
ICNIRP:5 kV/m, 0.1 mTCENELEC:10 kV/m, 0.64 mTNRPB:12 kV/m, 1.6 mTIRPA:5-10 kV/m, 0.1-1 mT
Present-worth analysis
( ) Aii
iP n
n
)1(11
+−+
=
i =10 percent
0 30 US$41.87
P
Transformer life
Time
02468
1010 12 14 16 18 20 22 24 26 28 30
Loss
cos
t as
a P
erce
ntag
e of
tr
ansf
orm
er c
ost
Years
V. Reduction of core losses
Core with step-lap joint
x
y
Steel Lamination
Ti
d
Lo
ns
g
Design of wound core
D F
G
E
m
turnn B
VA )(37513=
,2DAE e= ( ) ekgnfe FWPW =
4.62
2.27
5.60
3.27
5.35
2.853.53
2.85
4.76
2.30
4.23
2.13
0.00
2.00
4.00
6.00
pu
15 30 45 75 113 150
Transformer rating (kVA)
D/E G/F
LHL windings
020
4060
80100
120140
160
4 6 8 10 12 14 16 18 20 22 24 26 28
AWG size
win
ding
tens
ion
(kg)
Maximum tension Minimum tension
Experiments with core parameters
Sample Longitud traslape (cm)
No load losses (W)
1 2 49.01
2 1 47.49
3 1 44.24
4 1 46.61
5 2 55.38
6 1 51.42
7 2 53.58
8 1 50.18
9 1 48.98
10 2 55.11
11 1 50.88
12 1 50.03
Simulations using FEM
NeumannMagnetic flux trajectories for an air gap of 3mm and overlap length of 1.0cm, a) Two laminations per step; b) Eight laminations per step
a) b)
Emisions of power plants
(50,000,000transformers)( 6.43 W)(8760 hours/year)(30 years) = 84,490,200,000 kWh.
(84,490,200,000 kwh)(9800 BTU/kwh)=828,003,960 MBTU
Present worth analysis
i =10 percent
0 30 $3.79
P
Transformer life
Time
02468
10
Loss
cos
t as
a pe
rcen
tage
of
tran
sfor
mer
cos
t
Time (years)
( ) Aii
iP n
n
)1(11
+−+
=
VI. ConclusionsReduction of losses in three key elements of transformers.Extensive measurements of the load-loss test and no-load test were carried out on the test transformers.Tank losses were reduced 90 W using electromagnetics shielding.Tanks losses were reduced 200 W using T plate of stainless steel in a pad-mounted transformer.
ConclusionsBehaviour of no-load losses during the manufacturing of distribution transformer. Core losses were reduced when overlap distance were reduced from 2 cm to 1 cm.
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