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Introduction to Technical Loss of Power System

The Third Country Training Course

Technology Improvement for Transmission and Distribution in Iraq

November 2008

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Major Factors of Power LossMajor Factors of Power LossPower Plant

Losses of Transformer

Consumers (Domestic,Industrial,Commercial etc.)

Losses of Transmission Line

Losses of Distribution Line

Substation

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Transmission/Distribution Losses and Total LossesTransmission/Distribution Losses and Total Losses

A

B

Consumer

Substation

Distribution pole

500 kV 187 kV 66 kV 6.6 kV 100 V or 200 V

Transmission loss Distribution loss

A

Electric power

consumption in P/S

Electric power

consumption in S/S

PS SS SS SS B

Transformer loss (1)

Transmission loss (1) Transformer

loss (2)

Transmission loss (2)

Transformer loss (3)

Transmission loss (3)

Distribution loss (1)

Transformer loss (4)

Distribution loss (2)

Transformer loss (5)

Watthour meter

Power station

Substation

Electric power consumption in S/S

Electric power consumption in P/S

Transmission loss

Distribution loss

Consumption

in P/S

Consumptionin S/S

Transmission and distribution

loss

Total loss

Am

ou

nt o

f g

en

era

ted

/rece

ived

p

ow

er

Am

ou

nt o

f d

em

an

de

d

po

we

r

Ｃ

Ｄ

Transmission loss

Distribution loss

C

D

Transmission and distribution loss S

up

ply ca

pa

city a

t sen

din

g e

nd

Su

pp

ly cap

ab

ility a

t de

ma

nd

en

d

Total loss rate =1-B/A

Transmission and Distribution loss rate

=1-D/C

PS

SS

*

Excluding the consumption in P/S

Including the consumption in S/S

Substation (for distribution)

Step-up TR

Electric power

consumption in S/S

Electric power

consumption in S/S

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Major Factors of Power LossMajor Factors of Power Loss

Resistance Loss

Corona Loss

Dielectric Loss of CableCopper Loss & Iron Lossof Transformer

Loss of T.L

Loss of D .L

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Resistance Loss Resistance Loss (general formula)(general formula)

Where : Line Current [A] : Resistance of one line [ /m] : Length of the Line [m]

When current flows through T.L. or D.L. which have Resistance, Joule heat that corresponds to Resistance Loss generates:

Resistance Loss is as follows: ][Ww

dxriwL

o x 2

irL

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Resistance Loss Resistance Loss (Overhead T.L)(Overhead T.L)

Where, : Charging current [A]

: Power factor

(In case of a short-distance)

LrIw 23

cIcos

Where, : Line Current [A]

: Resistance of one line [ /km]

: Length of the Line [km]

IrL

(In case of a long-distance)

22 3/1cos3 IcIcIILrw ・・

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Resistance Loss (D.L.)Resistance Loss (D.L.)

Where, : Sending-end current [A] : Dispersal loss factor

Current is not constant except the case “Concentrating on the end of line”. Therefore;

xi

rLhIdxriw m

L

o x22

mIh

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Resistance Loss (D.L.)Resistance Loss (D.L.)<Load Distribution and Dispersal Loss Factor>

Concentrating on the end of line

Dispersal loss factor

Model of dispersal load

Distributing equally on the lineIncreasing, so that it goes to the end of lineBecoming the maximum in the middle of lineDecreasing, so that it goes to the end of line

%333

1

1

%5315

8

%205

1

%3860

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Corona Loss Corona Loss (Overhead T.L)(Overhead T.L)

In case of a transmission line with voltage higher

than about 100kV, if the conductors which size of

diameter is too small for the specific voltage use,

voltage potential gradient on conductor surface

becomes high, and occurs partial breakdown of the

air insulation.

Corona discharge occurs, and causes corona loss.And it is significantly affected by some external

factors. (from weather condition, such as water or snow deposit on the conductor)

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The losses of Overhead T.L.The losses of Overhead T.L.

A Comparison of Transmission Losses among Different Overhead Lines

Class

Yearly electric loss energy (MWh/100 km ･ circuit ･yr)

RemarksResistance

lossCorona loss Core loss Total

154 kVTACSR 610 mm2

(1 conductor)

57,700(99.3)

8(Negligible)

410(0.7)

58,118(100)

Figures in parentheses are composition ratios (%).

275 kVACSR 410 mm2

(4 conductors)

20,100(98.8)

54(0.3)

180(0.9)

20,334(100)

500 kWTACSR 810 mm2

(4 conductors)

11,000(94.2)

440(3.8)

240(2.0)

11,680(100)

Note: Input current: I = 1,000 (A); annual load factor: f = 0.6; loss factor: η= 0.432

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Dielectric Loss of CablesDielectric Loss of Cables (Underground T.L./D.L. )(Underground T.L./D.L. )

tanE

CfW nd

2

32

　　　 is in proportion to the squire of voltage ”V ”. Therefore, if the voltage is higher than 22kV, the dielectric loss of cable cannot be disregarded.

dW

Where, : frequency [Hz] : Static capacity [ F/km] : Line-to-line voltage [kV] : Dielectric loss tangent

fnCEtan

Single-core type

Sheath

ConductorInsulating Material

Semi-conducting

layer

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The losses of Underground T.L.The losses of Underground T.L.Transmission Losses in Underground Cables

Type of

cable

Applied voltage

(kV)

Capacity (MW)

Yearly electric loss energy (GWh/20 km ･ circuit ･ yr)

RemarksResistance

lossDielectric

lossSheath

lossTotal

OF2000 mm2

154100

0.44(20)

1.68(70)

0.09(4)

2.21(100) e ･ tan

=3.4×0.2%

2001.77(47)

1.68(44)

0.35(9)

3.80(100)

275200

0.52(11)

4.10(86)

0.15(3)

4.77(100)

4002.09(31)

4.10(60)

0.61(9)

6.80(100)

500400

0.64(7)

8.57(90)

0.27(3)

9.48(100)

6001.43(13)

8.57(81)

0.6(6)

10.6(100)

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Copper Loss & Iron Loss of a TransformerCopper Loss & Iron Loss of a Transformer

Copper Loss

Eddy current loss

Winding resistance Loss

Loss

Load loss

Non-Load loss Hysteresis

lossIron Loss

Auxiliary equipment loss

Cooling Fan lossOil pump loss

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Copper Loss & Iron Loss of a TransformerCopper Loss & Iron Loss of a Transformer

Iron Loss (Non-load Loss) Loss with steady value that

generates in an energized state, regardless of the value of the current.

Iron loss is mainly categorized to “Hysteresis loss” or “Eddy current loss”.

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Copper Loss & Iron Loss of a TransformerCopper Loss & Iron Loss of a Transformer

Iron Loss (Non-load Loss) <Hysteresis loss> The direction and magnitude of

magnetic flux in a coil constantly changes due to AC current, and it causes the friction loss between molecules.

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Copper Loss & Iron Loss of a TransformerCopper Loss & Iron Loss of a Transformer Iron Loss (Non-load Loss)

< Hysteresis loss>

: Hysteresis Loss : Frequency : Maximum Magnetic Flux Density : Proportional Constant

<Hysteresis Curve> horizontal axis ： Magnetic Field

Intensity H vertical axis ： Magnetic Flux

Density B

6.1mhh fBkP

hPf

mB

hk

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Iron Losses of a TransformerIron Losses of a Transformer

Conventional

core

Improved Core

JIS Type(NOTE)

35G165 35P135 35P115 30P105

Core Loss(w/kg)

(%)

1.65

(100)

1.35

(82)

1.15

(70)

1.05

(64)

(NOTE) The first 2-digit represents the value of the thickness (mm) multiplied by 100.

G means a normal material, and P means a high-orientation material.

The last 3-digit represents the guaranteed value of core loss which is multiplied by 100.(at the 50 Hz frequency and 1.7T flux density.)

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Copper Loss & Iron Loss of a TransformerCopper Loss & Iron Loss of a Transformer Iron Loss (Non-load Loss) < Eddy current loss> Magnetic flux change causes an electro motive force

and an eddy current is induced within the core, causing resistive heating.

: Frequency

　　 : Maximum Magnetic Flux Density : Eddy current loss :Resistivity of magnetic material : Thickness of iron plate : Proportional Constant

2

mee

fBtkP

eP

f

mB

ekt

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Copper Loss & Iron Loss of a TransformerCopper Loss & Iron Loss of a Transformer

Copper Loss (Load Loss) Load current flowing through the

winding causes resistive heating of the conductors.

Copper Loss is proportional to the square of the load current. ( )

RI 2

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Thank You!Thank You!

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Copper Loss & Iron Loss of a TransformerCopper Loss & Iron Loss of a Transformer Definition (IEC 60076-1*) Copper Loss (Load Loss) = the absorbed active power at rated

frequency at reference temperature associated with a pair of windings when rated current is flowing through the line terminals of one of the windings, and the terminals of the other winding are short-circuited. Further windings are open-circuited.

(*)”Power Transformer – General”

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Copper Loss & Iron Loss of a TransformerCopper Loss & Iron Loss of a Transformer

Definition (IEC 60076-1) Iron Loss (Non-load Loss) = the active power absorbed when

rate voltage at rated frequency is applied to the terminals of one of the winding, other winding or winding being open-circuited