Weird Breaker Tripping

[ThePunisher]

Hi all,

We have a strange condition wherein, our 600V switchgear power circuit breaker is tripping at no fault condition.

Here is the current case:

The switchgear is a main-tie-main with N.O. bus tie circuit breaker. The breaker is an 1600A K-Line breaker with solid state trip unit. The relay internal trip unit operates a lockout relay which in turn blocks closing of the the NO tie breaker. The tie breaker can be manually operated by close command pushbutton provided either or both incomer breakers are open and there is no lockout relay trip.

Automatic open transition transfer occurs when there is undervoltage or no no voltage at the line side of either incomer circuit breaker and no lockout trip.

Weird condition.

The incomer breaker A trips with no fault...the reason being is that the lockout relay did not operate nor the breaker registers a trip alarm indication. Because of this, the tie breaker can be closed locally/manually.

Is there any experience here for such weird condition? The breaker was replaced with a new one and still behaves the same way.

 

[waross]

There is not enough information given Punisher.
Can you post a diagram of your system?
Is this new equipment or is this a condition that has developed on existing equipment.
What has changed?
Is the incoming voltage trending higher or lower than previously?
Has any wiring, relays or other components been changed?
Have any new loads or equipment been added downstream?

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[RRaghunath]

It could either be intertrip from the upstream breaker to the incomer-A breaker! Intertrip doesn't initiate any protection and also doesn't cause lockout of the breaker.
Other possibility is a fleeting second earth fault in DC system that is causing the trip contact to be shunted owing to its (the second earth fault) location. This kind ghost trips are common in stations where people leave DC system earth faults (first one) unattended.

 

[cranky108]

Or it could be a bad close latch, where it does not trip, but the latch releases.

Not all breaker openings are a trip.

 

[jfpe]

My initial though was the same as cranky108 - bad latch, but the OP says they replaced the breaker. What are the odds of installing a new breaker with the same failure?

-JFPE

 

[davidbeach]

Under voltage release that isn’t satisfied when the breaker closes?

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[cranky108]

jfpe-anything that can happen, will happen.