MV Breaker 86BF Trip
MV Breaker 86BF Trip
(OP)
I was hoping to get some in input on potential root causes for the activation of an 86 lock-out relay specifically used for a breaker failure feature (referred to as 86BF on the attached drawings). We took down a large portion of our facility due to the activation of this 86BF that I found to be tripped with no trip command sent from the protection relay. There was no fault, or equipment damage found. Equipment was energized again with no issues; 86BF reset just fine.
This has actually happened before on this same switchgear/breaker line-up but not on the 86BF, rather just the 86 lock-out relay that trips the local medium voltage breaker; breaker was tripped, 86 was found tripped but the protection relay did not issue a trip command.
The circuit seems pretty simple, so I'm not really sure how that 86BF lock-out relay coil could have been energized. It sits on a 125VDC system, that typically operates 130-133VDC. The indicator light is a full voltage (direct connected) LED, that was found to be working just fine after the event.
Thanks in advance.
This has actually happened before on this same switchgear/breaker line-up but not on the 86BF, rather just the 86 lock-out relay that trips the local medium voltage breaker; breaker was tripped, 86 was found tripped but the protection relay did not issue a trip command.
The circuit seems pretty simple, so I'm not really sure how that 86BF lock-out relay coil could have been energized. It sits on a 125VDC system, that typically operates 130-133VDC. The indicator light is a full voltage (direct connected) LED, that was found to be working just fine after the event.
Thanks in advance.






RE: MV Breaker 86BF Trip
RE: MV Breaker 86BF Trip
RE: MV Breaker 86BF Trip
Vibration is possible although this substation is fairly remote on the facility (fenced it). Moisture could explain the irregularity of this event.
With regards to a DC transient, that is actually the path that I originally started down, and I'm having trouble believing it due to how high the "threshold" (pick-up) voltage is listed on the LOR specifications. It's listed at around 70VDC. Right now the indicator light is basically taking the full voltage drop of the circuit across it. That said, I'll probably need to get the component (light and LOR coil) impedances and work out the voltage divider as you mentioned to help prove or disprove this theory. I'm curious how high my DC voltage would need to be in order to reach a possible threshold voltage. I read a white paper from GE that stated you can have nuisance trips at less than half of the lower operating range of your coils. Good note to keep in mind for this type of event.
RE: MV Breaker 86BF Trip
RE: MV Breaker 86BF Trip
RE: MV Breaker 86BF Trip
When maintenance testing a 125VDC LOR (ramping up DC voltage for minimum pick up), it is not uncommon to find pick up at around 30 Volts for an ES Series 24.
RE: MV Breaker 86BF Trip
RE: MV Breaker 86BF Trip
Could you post a print screen of it?
RE: MV Breaker 86BF Trip
The light is built into your LOR relay from your drawings. I have seen multiple LOR relays trip due to internal circuit fail in the LOR light circuit.
RE: MV Breaker 86BF Trip