Operation of circuit breaker - does it require a pulsed or sustained trip signal?
Operation of circuit breaker - does it require a pulsed or sustained trip signal?
(OP)
For a typical distribution level circuit breaker, how long does the trip signal from the associated protection relay have to be maintained before CB tripping is insured (i.e. the operation becomes irreversible)? Is a pulse trip signal all that's required or does it need to be maintained for a sustained period of time? Also, is this standard to all CBs or does it vary between models?






RE: Operation of circuit breaker - does it require a pulsed or sustained trip signal?
If it is a Molded Case or Insulated Case Circuit Breaker, the pulse will have to be long enough to energize the coil of a solenoid that is operating the trip mechanism, called the "shunt trip" coil. That length will vary, but the longer the better because in the shunt trip mechanism, the coil circuit passes through a Normally Closed set of auxiliary contacts that change state immediately when the mechanism moves. So even a sustained signal is automatically removed from the solenoid coil once the desired effect has taken place (this is done to prevent burning out the solenoid coil). Too short of a signal, i.e. milliseconds, and the coil may not fully develop the necessary flux to operate though. Only the breaker mfr will know the minimum signal duration to ensure that it operates, but if you give is a one second pulse, you will be fine no matter what.
If we are talking Power Breakers, i.e. VCBs or ACBs, the they often use an impulse trip circuit that is backed up by a charged capacitor to store the trip coil energy. So in that case they will have a much shorter pulse length requirement, i.e. 3ms minimum, but also a much shorted MAXIMUM signal length, because there is an electronic firing circuit facilitating the faster trip time, and that circuit can over heat. So I have seen typically a maximum signal duration of 1 second on those, maybe less (GEs ED trip coil is where I got those values by the way). YMMV
"Will work for (the memory of) salami"
RE: Operation of circuit breaker - does it require a pulsed or sustained trip signal?
RE: Operation of circuit breaker - does it require a pulsed or sustained trip signal?
RE: Operation of circuit breaker - does it require a pulsed or sustained trip signal?
xnuke
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RE: Operation of circuit breaker - does it require a pulsed or sustained trip signal?
The breaker local control circuit will have a 52a contact in series with the trip coil circuit to de-energize the trip coil when the breaker opens.
The short answer to your question is to maintain the trip signal for at least nine cycles to assure that the trip coil operates.
RE: Operation of circuit breaker - does it require a pulsed or sustained trip signal?
In other applications, as noted above, output can be a one-shot with several cycles of duration to allow the breaker sufficient time to open.
old field guy
RE: Operation of circuit breaker - does it require a pulsed or sustained trip signal?
Why protective relay should be monitoring the breaker status?
protective relay will reset after breaker( main contact) open and primary current extinguish.