86 Lockout Relay: Trip Breaker Or Close Coil Inhibit?

Tony, thanks for the reply.

On the LV side it is a Schneider Electric (Square D) 6000 A switchboard. The breakers are manual.

On the MV side it is an ABB gear with ADVAC breakers and electric closing coil.

We will leave it up to the customers for the MV side. LV side will remain with shunt trip only.

Thanks again!

I think you've answered your own question. The LV breakers are manually operated (except for the shunt trip, which the 86 activates). There is nothing electrical that a contact of the 86 can block in the close mech.

Yes Peter, there is nothing that the 86 can block or inhibit on the LV.

The question now is if we should just trip on the MV breaker or inhibit close coil when 86 is tripped.

If there is any automatic reclosing on the MV breaker, you should use a blocking contact in the close circuit. The other reason to possibly add a block close is if you are concerned that something could remove the trip signal from the breaker without having reset the relay and/or lockout. In this case it gives an additional measure of confidence that the breaker won't be closed onto a fault.

Other than that, the trip contact from the 86 should do the job. If the trip is held and the breaker gets a close signal, it will try to close, but will the mech will cycle right into the trip - it's called a "trip-free" condition. The contacts don't actually close, but the mech goes through the (beginning) motions of closing, but then goes right back open again.

I was not familiar with the "trip-free" condition. Our concern is not allowing to close the breaker to a fault. That is, after all, the whole purpose of the lockout relay.

The way I understood it was that the breaker actually closed only to be immediately tripped again. The trip-free condition makes much more sense though. Thanks!

Although the breaker will attempt to close the shunt or UV coils will operate the moment the mechanism starts to move. The main contacts will never reach the point of closing the circuit.

I'm not sure about ABB but with Merlin Gerin MasterPac ACB's unless the UV coil is energised the mechanical closing button is disabled.

They're from the same stable so I can't see there being a difference.

An auxiliary relay (anti pumping relay) can prevent alternate tripping and closing of the circuit breaker if closing command persists during fault. This trip free mechanism is ensured by the anti pumping relay which prevents hunting (i.e. continuous closing, opening operation) of the circuit breaker. The function of this relay is to cut off the supply to 52C (CB closing coil) until the tripping condition is eliminated and the trip lockout relay 86 is reset.

The anti pumping relay cannot know by its own that the fault condition is eliminated. It only prevents continuous close trip of the breaker in the event if somebody gives close command & couldn't release the button in such a short time.

When the trip lockout relay (86) is reset after the fault is identified and eliminated, fresh command can be given for closing the circuit breaker. The NC contact of anti pumping relay in the closing circuit will permit the circuit breaker to close provided the spring is charged.

Once the anti pumping relay is latched, the supply to closing coil of the circuit breaker will be cut off as long as the closing command is present.