Dedicated 24VDC Supply for shunt trip breakers and protective relays 3

[kleppik]

I am working on grid connecting a synchronous generator. The control signal to trip the generator circuit breaker is 24VDC. 24VDC is also used to power the generator protective relay and intertie protective relay.

This 24VDC (a battery bank) is also used for cranking the prime mover. Is there a UL or CSA or IEEE standard that requires a dedicated supply for the shunt trip signal or protective relays?

 

[kleppik]

In the 24th edition of the Ontario Electrical Safety Code, the requirement for the circuit breaker (and its associated control circuits) battery not to supply any other loads has been deleted. Still good design to have separate supply though.

 

[xxjohnh]

It seems to be a trend. I have recently seen a design where all the DC requirements 220/110/24 DC and UPS are all supplied by two redundent battery banks. Lower DC voltages are supplied by power supplies from 220v DC.

 

[ScottyUK]

And if you let them go too far down this path they will install VRLA batteries to hold up the critical services board. Engineering by accountants, gotta love it...


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If we learn from our mistakes I'm getting a great education!

 

[rcw retired EE]

kleppik- My apologies, I looked at the 23rd edition, 2002 of th OESC. I should have checked the latest.

 

[xxjohnh]

Too late they are already using 2 x 100% VRLA batteries and everything is 100% modularised. Standard vendor package.

 

[rbulsara]

There is no shortage of bad designs in the world. Keeps us busy..

Rafiq Bulsara

http://www.srengineersct.com