utility switchgear requirements 1

[un421ate1]

The local utility requires two indicating lights on the front of their 13Kv switchgear to indicate the position of a generator air-circuit breaker installed downstream that operates in parallel with the utility.
Because of a shortage of auxilliary contacts on the generator air circuit breaker I used the one available "A"
contact to energize a relay and used its n/o, n/c contacts
to power the indicating lights (red closed..green open).
The engineer said this arrangement violated ANSI standards
and that the lights must be powered through mechanically linked generator breaker contacts..
Is he correct and if so what's the relevant code requirement.
many thanks.

 

[jbartos]

Suggestion: Check with a manufacturer of similar equipment for the standard number and clause, e.g.

http://www.tti.bc.ca/products/sys2000/TTI-System2000.pdf

 

[busbar]

There is a publication on relay trip circuit design by the IEEE Power System Relaying Committee. The report section on trip-circuit monitoring and supervision with respect to indicator lamps should be carefully considered. Their site is pes-psrc.org.

Practices in switchgear construction may not be referenced in codes, but are accepted and considered essential in the industry. The rationale for some may not be immediately apparent, but have a track record of reliability and operational standardization.

 

[davidbeach]

If everything is working correctly, other than during the few cycles of breaker switching time, assuming that 52B = not(52A) is almost always correct, but during breaker malfunctions you can get sustained conditions where you would have either both 52A and 52B or neither 52A and 52B.

In other words, not open does not necessarily equal closed and not closed does not necessarily equal open. Should, but don't always.

 

[alehman]

With the relay scheme you would want to have a cell position contact in series with the indicator lights so neither is on when the breaker is racked out. The use of a relay in this application defeats the purpose of having two indicator lights and should not be accepted.