Transcript Snímek 1 - cidel argentina 2010

THE VERIFICATION
OF SHUNTING METHOD
FOR LIMITATION OF EARTH
FAULT CURRENT IN MV
COMPENSATED NETWORKS
Petr TOMAN
Jaroslava ORSÁGOVÁ
David TOPOLÁNEK
Vladimír BLAŽEK
Brno University of Technology
Jaromír DVOŘÁK
E.ON Czech Republic
Objectives
• Try to find out the reason of damaged concrete
towers in the distribution network
Objectives
• Try to find out the reason of damaged concrete
towers in the distribution network
• To measure the voltage and currents during the
earth fault for fault on unearthed console of
concrete tower and for other types of fault
• The method of shunting (connecting affected
phase to earth system in substation) should be
tested
• The conditions during the fault state should be
the same as in normal operation
The network
• The distribution grids (22 and 35 kV) in the
Czech Republic are operated as compensated
via Petersen coil or as earthed via resistor
(urban predominantly cable grids)
• When the earth fault comes the automatic of coil
tuning stops and the dispatcher tries to find out
the point of fault. During this process the
mistuning caused by switching operation could
rise
The measuring
Six types of fault were realized
– Low impednace – conductor lying on the earth
– Arc - spark gap
– Arc - damaged MV cable
– 400 W
– 1600 W
– Unearthed console of concrete tower
The measuring
The size of the network was 140 A:
– Tuned Petersen coil
– Mistuned Petersen coil about 40 A low
All experiments was made in three places of
fault:
– Close to substation (busbar)
– The long distance (about 25 km) from busbar
– The middle distance (about 12 km) from busbar
busbar
L1 L2 L3
Transformer
110kV/22kV
Petersen
coil
Shunting
circuit breaker
Line 1
Line 2
Fault
The time sequence of fault
1.
2.
3.
4.
Switch on the fault
Switch on the shunting circuit breaker
Switch off the fault
Switch off the shunting circuit breaker
Tuned coil
Mistuned coil
Earth fault on
unearthed console of
concrete tower
-tuned coil
Earth fault on
unearthed console of
concrete tower
- mistuned coil
Earth fault on unearthed console
Conclusion
• The longer operation of earth fault
on unearthed console of concrete tower
could be very dangerous for the lifecycle of
towers
• Fault currents after closing shunting circuit
breaker decreased practically to zero during all
experiments
Conclusion
• DSO on the base of series of experiments
decided about the pilot project of shunting in
substation Medlanky in the periphery of Brno
city.
• The equipment could shortly make the second
earth fault in substation in the other phase.
Conclusion
• The next series of experiments are prepared.
The main aim is to verify touch voltage for
specified cases and evaluate the possibilities of
fault location by distance principle (during
double earth fault)
Thank you for your attention!