20-08-2013, 02:15 PM
SETTING AND TESTING OF OVER CURRENT RELAY USING ETAP
SETTING AND TESTING .pdf (Size: 398.19 KB / Downloads: 28)
INTRODUCTION:
In this lab we take a system on which we perform load flow
analysis and then we select the current transformer for our system.
After selecting current transformer given overcurrent relays were
selected. The relays used are “7SJ602” and “SPAJ140C”.Then for each
relay type characteristic curve and pick up value was selected and at
the end we tested design for the fault.
OVERCURRENT RELAY:
NEMA numbers are 51 and 50. Overcurrent relays are used for
protection of lines, transformer, generators, and motors.
The protection must satisfy these requirements:
a) Under normal conditions the breakers are not tripped
b) Under fault conditions only the breakers closest to the fault on
the source side are tripped
c) If the closest breaker fails to operate, the next breaker closer to
the source should trip.
SELLECTION OF CT’s:
The load flow analysis is performed on the above
system. The overcurrent is considered more than two times of the
normal current as in above system normal current was 1600A.
The more than two time of which is approximately 4000A.So I
selected Current transformer of 1000 to 1.So for thousand
ampere at Primary it will give 1 ampere at its secondary.
CONCLUTION:
From the above results it is clear that given Siemens relay
have more time delay for the operation of backup relay then given ABB
relay .