Topics: What is Stuck Breaker Protection?
on General Discussion
What is Stuck Breaker Protection?
What is Stuck Breaker Protection ,& when it's requird ?
09-01-2014 03:04 PM
We call it circuit breaker failure protection .Relay which generates an output to trip the breaker has also one digital input port which can be used to sense the circuit breaker status weather close or open.When any breaker fails to trip after getting trip command from relay ( due to mechanical reason, trip circuit open, etc) and the relay doesn't get the breaker open status within a stipulated time , then the same relay will issue a trip command to the upstream circuit breaker to isolate the fault.
09-01-2014 05:34 PM
Thanks for support ,
is there any interfernce betwenn Stuck Breaker Protection & Partial Busbar Diffrential .
09-01-2014 08:30 PM
As the name indicates, the breaker is STRUCK in its closed position due to some mechanical problem/s , even after receiving the trip command , breaker is not opening - a very serious problem.
In numerical relays, BF protection starts the moment trip signal is generated by any feeder protection.
Current check relay & a follower timer being the main ingredients of BF protection, current check relay checks the presence of current in faulted circuit and if the current persists beyond a preset time ( normally 120 ms ) , will trip all the breakers connected to the section of the bus to which struck breaker is connected.
If the feeder happens to be OHL, to arrest fault infeed from remote, remote end breaker is tripped through carrier channel.
09-01-2014 10:35 PM
It is not simply BF protection. When there are more than one busbar section, there will be a bus section breaker. Each bus section will have one incoming feeder and several out going feeders. In case a feeder breaker not clearing the fault, there is a chance that both incomers will trip. It is difficult to coordinate O/C +E/F relays in the bus section panel to trip with proper discrimination. The solution is: provide two identical set of CTs on both side of the Bus section breaker. Then there will be stuck breaker OC+EF relays on either side of the bus section (total two sets). There will be similar CTs in each incomer feeder also. Left side incomer CT will be paralleled to right side CT in the bus section panel. Similarly right side incomer CT will be paralleled to left side CTin the bus section panel. On feeder fault, the current in the Stuck breaker relay will be the sum of bus section current + connected incomer current. This is a large qty and will trip bus section CB before the healthy side incomer trips. ultimately only one incomer Cb and bus section will be tripped and other section and all its out going feeders will be safe. This can also be called partial busbar diff protection.
09-02-2014 01:27 AM
If any one finds difficult ask again please
09-02-2014 04:05 AM
@M.C.Mohanan Nair , If not simply BF , then what is it ? What you have posted above is partially true about how the other breaker/s isolate the faulty circuit , but not the concept of Breaker Failure protection.
Your above explanation can also be read as BF is part of 87BB, If yes, it is true to some extent , up to 220kV , many numerical, low impedance 87BB relays do have BF function in built in them, I have worked on many 220kV protection schemes with no separate BF relays.
How do you explain a dedicated , stand alone BF protection relays on 400kV & above systems ? Also, your statement " On feeder fault, -------------------------------------------- " does not appear to be most appropriate BF concept.
09-02-2014 06:17 AM
Dear krishna, Stuck CB protection is not used in HV system. It is for MV system like 11, 22 33 Kv etc where switchgear-bus panels are used. It is a cheap way for safe guarding the substation from total shut down. In BF relay, typically there is current check, CB contact check etc. More over the main relay or the trip relay will initiate a timer of the BF relay. So Stuck breaker protection is not BF protection. Even if it is builtin or descrete, BF protection principle is the same. It needs an initiation. First of all I did not mention MV or HV. Stuck B protection is not for HV/EHV. Why it is called Partial BB protection? any one can guess, in case of a bus fault in 11KV bus, it will trip bus section CB and incomer CB so that the other incomer and feeders will be unaffected. However this relay will not trip out going feeders as in BB protection, and so all feeders should be radial with out any interlinking or feedback. I did not attribute SBP as BF protection. If not still clarified call to 09633476565. You may read my previouse posting" ON FEEDER FAULT HANGING UNCLEARED DUE TO DEFECTIVE CB OR A BUS FAULT....................................."