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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
Frankfurt (Germany), 6-9 June 2011
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
Wurm – Austria – Session 3 – 0915
Cause
Frankfurt (Germany), 6-9 June 2011
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
Wurm – Austria – Session 3 – 0915
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
Frankfurt (Germany), 6-9 June 2011
Wurm – Austria – Session 3 – 0915
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
Positive sequence impedance of line
IE
busbar phase L1
UNE
N
d
fault impedance
earth impedance
Frankfurt (Germany), 6-9 June 2011
Wurm – Austria – Session 3 – 0915
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
Positive sequence impedance of line
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
Frankfurt (Germany), 6-9 June 2011
Method A:
Method B:
Wurm – Austria – Session 3 – 0915
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
Frankfurt (Germany), 6-9 June 2011
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
Frankfurt (Germany), 6-9 June 2011
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
Wurm – Austria – Session 3 – 0915
Preparation of field test and installation
Frankfurt (Germany), 6-9 June 2011
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
Wurm – Austria – Session 3 – 0915
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
Frankfurt (Germany), 6-9 June 2011
Start: January 11th, 2011 Aim:
calculated fault distance should indicate the fault position within one third of the total length of the feeder.
Wurm – Austria – Session 3 – 0915
Preparation of field test and installationcircuit
breaker resistor
Hope: a lot of earth faults until presentation at CIRED 2011
Frankfurt (Germany), 6-9 June 2011
Fault 1:
Split of conductor in L2:
X,real = 3,73 X,classic = 1,41 X,improved = 2,98
Wurm – Austria – Session 3 – 0915
Results
V1E
V2E
V3E
VNE
IR
IL
23 A
Frankfurt (Germany), 6-9 June 2011
Fault 2:
??? in L1
X,real = ??? X,classic = 10,09 X,improved = 3,88
Wurm – Austria – Session 3 – 0915
Results
V1E
V2E
V3E
VNE
IR
IL
55 A
Frankfurt (Germany), 6-9 June 2011
Wurm – Austria – Session 3 – 0915
Thank You for Your attention!