WE HAVE INSTALLED 20 mVA 6.6 kV / 11 kV DELTA-STAR CONNECTED TRANSFORMER IN OUR PLANT. FOR THIS WE HAVE USED FOLLOWING FEEDERS ALONG WITH DETAILS
6.6 kV SOURCE BRK CT RATIO - 1000/1 A, ABB MAKE RET 615 RELAY
11 kV INCOMER CT RATIO - 600/1 A EASUN REYROLLE CSC 211 RELAY
11 kV OUT GOING FEEDER CT RATIO - 400/1 A EASUN REYROLLE CSC 211 RELAY
AFTER INSTALLATION THE SOURCE BREAKER IS TRIPPING ALWAYS FOR EARTH FAULTS IN THE 11 kV FEEDERS.
THE EARTH FAULT RELAY SETTINGS ARE AS BELOW ( In - SEC CURRENT )
MAX LOAD TAKEN AS 4250 kVA for 6.6 kV SOURCE BREAKER - RET 615 HIGH SET E/F -0.2 X In - TIME 50 m sec, LOW SET E/F 0.15 X In - TIME 200 m sec
MAX LOAD TAKEN AS 2500 kVA FOR 11 kV OUT GOING BREAKERS - CSC 211 RELAY HIGH SET E/F -02 X In - TIME 200 m SEC LOW SET E/F 0.45 X In - TIME 175 m SEC
INSPITE OF THIS TIME SETTINGS IN DIFF VALUES THE SOURCE BREAKER IS TRIPPING ALONG WITH THE OUT GOING FEEDER BREAKERS
PLEASE SUGGEST/CLARIFY WHAT IS THE OPTIMUM SETTING TO BE ADOPTED TO AVOID SOURCE BREAKER TRIPPING FOR ANY FAULT IN THE O/G FEEDERS
PLEASE HELP
BYE BYE
Unwanted Tripping of Source Breaker
Re: UNWANTED TRIPPING OF SOURCE BREAKER
