Differential Relay Didn't Work While CT Exploded

<...IS IT NORMAL ?...>

NO.

Really,, Is there such as probability ?

Differential relay should have tripped if it is not damaged in the process. Perhaps the o/c current relay as well if set properly.

can you please give further details?... was the current transformer, (the one that exploded) included in the differential relay? (what i mean is that it is one of the inputs to the differential relay?)

if it is not, then the relay will not trip that is for sure..

CURRENT TRANSFORMER THAT EXPLODED IS AT THE SECONDARY SIDE OF THE POWER TRANSFORMER.

IT WAS BREAKEN UP IN TWO.

DIFFERENTIAL RELAY SHOULD HAVE TRIPPED CERTAINLY ?

THANKS..

Hi..

i hope you have already understand the problem you are trying to ask..

what i mean is that..(was the current transformer you used included in your differential relay?)

as it was clarified by jans.. if this current transformer was included in your differential, then make sure to check your differential relay...

if this current transformer is not included in your differential relay, then no tripping of differential relay is expected.

we normally ask for a seperate ct for differential protection wherever feasible.if not at least the differential core must be electrically the outermost core covering the metering core and perhaps the pt and la as well.on ct explosion many things are feasible.1)differential lv core opened-the differential relay would have tripped.

2) differential core shorted:then if the pilot resistance is considerable then the differential relay could trip.if the pilot resistance is much smaller than the differential relay impedance then the relay may not trip.

3)the cores are in tact but due to fault surge the differential rely may have damaged.For this reason also we prefer high speed relays since they can operate before a damaging surge builds up.

Pl. check if the differential relay is functional. When was the relay last tested.Pl. try to select a sensitive settings with proper biases.

Thorough periodic testing setting and commissioning exercises are not less important than installing the relay.

thanks a lot for ur reply