SEL-351 - ALARM output
SEL-351 - ALARM output
(OP)
If the SEL-351 fails, the ALARM output contact goes to 1. Is there any condition of failure where the ALARM relay word bit would not go to 1 as well?
I.E. instead of wiring the ALARM output contacts of the SEL-351 into the trip coil of the circuit breaker (relay failure would trip the breaker), why not just use the ALARM relay word bit in the TR trip equation instead of wiring the ALARM contact?
I.E. instead of wiring the ALARM output contacts of the SEL-351 into the trip coil of the circuit breaker (relay failure would trip the breaker), why not just use the ALARM relay word bit in the TR trip equation instead of wiring the ALARM contact?






RE: SEL-351 - ALARM output
RE: SEL-351 - ALARM output
Is this a common practice ?
RE: SEL-351 - ALARM output
RE: SEL-351 - ALARM output
Given Loss of voltage to the power supply will not cause the ALARM bit to assert, I would think, therefore, that one could add a low DC voltage word bit to the trip logic equation in addition to the ALARM word bit, and thus, mimic the ALARM output contact being wired to the trip coil of the breaker?
RE: SEL-351 - ALARM output
RE: SEL-351 - ALARM output
RE: SEL-351 - ALARM output
To do what you ask, you will need to wire the normally closed alarm output in parallel with the output used for the TRIP word bit. The no DC voltage will cause the alarm contact to go to its normally closed (deenergized coil) state. Of course all the other conditions the postors have mentioned above will also cause the contact to close.
RE: SEL-351 - ALARM output
Make sure and put a big sign on the wall that says turning the relay off will trip the breaker!!
RE: SEL-351 - ALARM output
RE: SEL-351 - ALARM output
And sometimes for no apparent reason at all.
RE: SEL-351 - ALARM output
Maybe it's my utility side bias, but I'm uncomfortable with stating the utility requirement is a bad idea when we have no idea why it is a requirement. Suggest we stick with stating the disadvantages and leave it there.
RE: SEL-351 - ALARM output
RE: SEL-351 - ALARM output
So maybe the concern is a lack of redundency, in which case I would look at other issues along the same line. There is an IEEE document on this whole subject (also a NERC document just to be redundit).