frankfurt (germany), 6-9 june 2011 manfred wurm evn netz gmbh, austria wurm – austria –...

Frankfurt (Germany), 6-9 June 2011

Manfred Wurm EVN Netz GmbH, Austria

Wurm – Austria – Session 3 – 0915

EARTH FAULT DISTANCE LOCALIZATION IN INDUCTIVE EARTHED NETWORKS BY MEANS OF DISTANCE

PROTECTION RELAYS


Earth fault location in inductive earthed grids:► detection of the faulty feeder in the substation► signalling to the system operator

Localization of earth fault position:► by means of commutations► personell must find the fault position

wish to get information about fault distance, e.g. Xprim


Cause


usually: natural residual fault current is too less to pick-up a distance protection device

therefore: increasing the faultcurrent by means of anadditional ohmic current(« pilot current »)in the neutralof the network


Principle and idea

Radditionally Zcoil

L1 L2 L3

E earthing system

transformer

healthy feeder(s)

faulted feeder

Positive sequence impedance of line

earth impedance

Busbar

N

d

ON 0,3 s



Fault calculation: conventional

E

EDist

IkI

UZ

01

1

d

dxIkI

UX L

E

EDist

'Im

01

1

Zneutral

L1 L2 L3

E earthing system

transformer

point of measuring: healthy feeder(s)

point of measuring: faulted feeder d·zL’

d·zE’

U1E

I1

IF


IE

busbar phase L1

UNE

N

d

fault impedance

earth impedance



Fault calculation: modified

Radditionally Zcoil

L1 L2 L3

E

Zearth Rearth

earthing system

transformer

point of measuring: healthy feeder(s)

point of measuring: faulted feeder Leitung

d·zL’

d·zE’

CE

ZF RF U1E

I1

Icap

IF


earth impedance

earth capacity of line

UF

IE

Busbar phase L1

UNE

N

Uearth

ITr

fault impedance

d

E

EFF

I

URZ

1Re

E

FFTrEDist

IkI

ZIearthZIUZ

01

1


Method A:

Method B:


How to obtain the realistic value of the fault current IF, measured at the busbar?

ENEEF CUjII 3

3Radd 3Zcoil

1:

poin

t of m

easu

ring:

fa

ulte

d fe

eder

Z1L

C12/2

RF

I1R

IF

E

busbar

U1R

C11 C1

2/2

Z2L

C22/2 C2

1 C22/2

Z1T

Z2T

Z0L

C02/2 C0

1 C02/2

Z0T

I1F

I2R

I2F

I0R

I0F

U1F

U2R0 U2

F

U0R U0

F

2:

0:

I1cap/2

I1cap/2

I0cap/2

I0cap/2

0 0

RFF III ²3²3


Three manufacturers Areva (now Schneider) Siemens Sprecher Automation

implemented the modified fault distance calculation in their existing relays

1st step: earth fault test and 2nd step: field test

in a 20-kV-grid of EVNWurm – Austria – Session 3 – 0915

Reality check


selection:area with difficult atmospheric conditions

substation with 4 outgoing feeders (20 kV),3 of them are test feeders► with mixed ratio of OHL and cable► equipped with one modified distance device of each manufacturer stated above

additionally installation of a fault recorder


Preparation of field test and installation


Size of pilot current:► Radd = 60 max. ≈ 200 A pilot current► on-time = 0,25 s

Influence of load current:(20 kV: 30 A ≈ 1 MVA)load current andpilot currentwill add


Further particulars

subs

tatio

n

normally openDISTO/C, directedrecloser

160A / 0,5s200A / 0,8s

200A / 0,5s

300A / 1,0s

300A / 1,0s

200A / 0,4s

0,05s / 0,8s / 2,5s 400A / 2,0s

0,05s / 0,8s / 2,5s 400A / 2,0s


Start: January 11th, 2011 Aim:

calculated fault distance should indicate the fault position within one third of the total length of the feeder.


Preparation of field test and installationcircuit

breaker resistor

Hope: a lot of earth faults until presentation at CIRED 2011


Fault 1:

Split of conductor in L2:

X,real = 3,73 X,classic = 1,41 X,improved = 2,98


Results

V1E

V2E

V3E

VNE

IR

IL

23 A


Fault 2:

??? in L1

X,real = ??? X,classic = 10,09 X,improved = 3,88


Results

V1E

V2E

V3E

VNE

IR

IL

55 A



Thank You for Your attention!

frankfurt (germany), 6-9 june 2011 manfred wurm evn netz gmbh, austria wurm – austria –...

Documents