01-Dist Part 1_new

8/7/2019 01-Dist Part 1_new

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Siemens AG 2006

Distance Protection for transmissionlines: part 1

Power Transmissionand Distribution


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Page 2 TLQ 2004 Distance Protection Part1

Siemens AG 2006

Power Transmission and Distribution

Why impedance protection?

Situation: Meshed network and two infeedsDirectional overcurrent time relays

0,6s

0,6s

0,3s

0,3s

0,6s

0,6s

0,3s

0,3s

non-selective trip


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Siemens AG 2006


Localization of short-circuits by means of an impedance measurement:

- fault on the protected line

- fault outside the protected line

Z1

relay A

selectivity

relay A

Z2

Basic principle of impedance protection


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Siemens AG 2006


Distance measurement (principle)

6 loops: 3 phase- phase loops and 3 phase- ground loops

phase- phase -loop:

The same applies to the remaining loops

U L1-L2 = Z L ( I L1 - I L2 )

Measured current measured voltage

Z L = R L + j XL

Z E = R E +j X E

IL1

IL2

IL3

IE

ZL

ZE

UL1 UL2 UL3


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Siemens AG 2006


phase-ground-loop: U L1 = - L1 ( R L + j XL )- - E ( R E +j X E)

- L1, - E measured current U L1 measured voltage

The same applies to the remaining loops

Distance measurement (principle)

IL1

IL2

IL3

IE

ZL

ZE

UL1 UL2 UL3

Z L = R L + j XL

Z E = R E +j X E


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Siemens AG 2006


Load and short-circuit impedances

ZLZLF1ZLF2

R F R FZLoadD

F1 F2X

R

ZL

ZLF2

NSC 1NSC 2

NL

RR

ZF1

ZF2

RR

ZLoad

ZLF1

Fault area

distance relayoperatingcharacteristic

Fault inreverse

direction Load area

Minimum Load Impedance:M inimum voltage 0,9 UnM aximum current 1,1 InM aximum angle s 30

Phase - Phase Fault

RR } RF / 2

Phase - Earth Fault

RR } RF /(1 + R E/R L)


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Siemens AG 2006


Principle of ( analog ) distance relayingISC

E

comparator

ZL

ZSC

ZReplica (line replica impedance)(corresponds to the set zone reach)

U1= k 1 USC = k 1 ISC ZSC.

U2=k 2 ISC ZReplica

ZS

R elay design:operation if

U1< U2i.e . ZSC < ZReplica

ZReplicaX

R

Ext . fault

Internal fault

A B


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Siemens AG 2006


Typical distance zone-characteristic

MHO-circle shifted circle

polarisedMHO-circle quadrilateral

ZR

ZSC

ZSC '

externalfault

internalfault

X

RN5

X

R

ZS = 0

ZS small

ZS high ZS

RF

ZL

X

R

centre

ZSC '

ZSC

setta le arccom ensati on

X

X

ZSC -L Rarc

RR


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Siemens AG 2006


Graded distance zones

time

D1 D2 D3

t1

t2

t3

Z1

Z2

Z3

distance

( t = grading time

A CB D

Z1 = 0,85 Z ABZ2 = 0,85 (Z AB + 0,85 Z BC )Z3 = 0,85 (Z AB + 0,85 (Z BC + 0,85 Z C D))

Safety margin is 15 %:- line error - C T, VT error - measuring error

Grading rules :


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Siemens AG 2006


2nd Zone: It must initially allow the 1st zone on the neighbouring feeder(s) to clear the fault .The grading time therefore results from the addition of the following times:

operating time of the neighbouring feeder mechanical 25 - 80 msstatic: 15 - 40digital: 15 - 30

+ circuit breaker operating time HV / EHV: 60 ms (3 cycles) / 40 ms (2 cycles)M V up to about 80 ms (4 cycles)

+ distance relay reset time mechanical: approx . 60-100 msstatic: approx . 30 msdigital: approx . 20 ms .

+ errors of the distance relay internal timers mechanical: 5% of the set time, minimum 60-100 msstatic: 3% of the set time, minimum 10 msdigital: 1% of the set time, minimum 10 ms

+ distance protection starting time *) mechanical: O/ C starter: 10 ms, impedance starter: 25 ms

static: O/ C stater: 5 ms, impedance starter: 25 msdigital: generally 15 ms

+ safety margin (ca.) grading; mechanical-mechanical: 100 msstatic/digital-mechanical or vice versa: 75 msdigital-digital or static-static 50 ms

*) only relevant if the set relay times relate to the instant of fault detection / zone pick-up . This is the case with all S iemens relays . There areother relays where the time is adapted by software to relate to the instant of fault inception . In the latter case the starting time has to bedropped .

Determination of grading times(With numerical relays 250 ms is possible)


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Siemens AG 2006


NSC

Cu rr t a r a f or f or a r d f a u lts

- SCCu rr t a r a f or r rs f a u lts

- SC

USC

R

ZSC

Z 'SC

I dan c a r a f o r f o r a r d f a u lts

I dan c a r a f o r r rs f a u lts

NSC

D t r i na tion of f a u lt d ir ction

cu rr n t / o lta g dia gr am impedan ce d ia gr am

Fa u lt loca tion Wh e r e is th e f a u lt ?

Th e impedan ce a lso sh ow s th e d ir e ction , b u t ....


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Siemens AG 2006


direction may be determined together with the impedance measurementbut: problems may arise in certain cases (e .g . close-in faults)

separate directional determination required!

Why impedance measurement and directional determination separately ?

line characteristic

fault with arc resistancein forward direction

fault in forward direction

fault in reversedirection

close-in fault

X

R

A B

Impedance measurement and directional determination


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Siemens AG 2006


Alternatives for the directional measurement

faulty phase voltage

V f

I f

V L2

V L3

voltage memory(pre-fault voltage )

I f

V L2V L3

V L1

healthy-phase voltage(phase to phase voltage )

I f

V f

V L2-L3 V L2V L3

~

~

~

~

~

~

~

~

~

Z lineZ grid relay

fault L1-E

Method 1 Method 2

V L1

V L1 V f


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Siemens AG 2006


Directional measurementSummery of all 3 methods

uRI = uL2-L3

u f = uL1

Distance measurement

Direction measurementwith voltage memory

Direction measurementwith unfaulted voltage

i f (t)uL1

if

if

if

uL2-L3

uL1Measuringwindow


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Siemens AG 2006


Fault detection techniques

Over-current fault detectionVoltage dependantover-current fault detection

Voltage andangle dependantover-currentfault detection

I

U

I >>I > I N >

R

X

Impedancefaultdetection

Not in 7SA522


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Siemens AG 2006


110 knet SCC ( )" 1 00 M

40 MuSC 120 k

400/1

l

I >st a rt 1 , I ND

OH -line95 /15 l/S tZ 'L , ; /km

' l)

10 20 30 40 50 60

I > start = 600 A

0,5

1,0

1,5

2,0

2,5

I SC (2) [kA]

l [km]

I SC(2) =U

N 1,1

2 ( Z S + Z S + Z L

reach of O C starter approx . 32 km

N T

Reach of over-current fault detection

ph-ph fault as an example

There is a limitationto the reach


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Siemens AG 2006


I I >>I >

UI >>

UI >

U

Udigital

electro-mechanical

Power system

Relay

line

E

E

ZSUSC

ZSCI SC

USC

- SC

USC

G

G

Voltage controlled overcurrent fault detection


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Siemens AG 2006


Voltage and angle controlled overcurrent fault detection(U-I-N-starting)

50 %

100 %

U/U N

I /I 1 2 3

I > I N > I >>

U( I N >) U( I >>)

X X

R R

N2

N1N1

N2

This method is used in Germany


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Siemens AG 2006


X

R

N LoadLoad

Z1

Z2

Z4

Z3

Z1B

Z5

Line

E

Impedance zones of digital relays (7 S A6 and 7 S A52)

Distance zones

Inclined with line angle NAngle E prevents overreach of Z1

on faults with fault resistancethat are fed from both line ends

Fault detection

no fault detection polygon: thelargest zone determines thefault detection characteristic

simple setting of loadencroachment area withRmin and NLoad


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Page 21TLQ 2004 Distance Protection Part1

Siemens AG 2006


Ring feeder: with grading against opposite end

0.6

0.3

grading time(s)

The same grading from both sides


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Page 22TLQ 2004 Distance Protection Part1

Siemens AG 2006


Grading in a branched radial system

L2

L3

L4

L1Z2

Z1

Z3

The impedances of the Z2 and Z3 must be grading with the shortest impedance

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