Breaker Failure Relay Setting

Set the TRIP signal to Breaker fail initiate the function.

Could you post the BF relay settings so I can help you better.

You question is confusing, can you explain more on what you are looking for.

If the breaker status or current flow is detected ,BF relay will work fine.

in first thank you for your attention,

ok sir i know this but the problem is the setting current is 400A primary while the maximum load current is 300A (at base load for the unit) so the question is how can the protection system detect the breaker fail at different loads less than the base load during the electromechanical trips (fire protection,buchloz,....)which havenot current effect.

from my point of view this setting caculated and was setted to operate the function at electrical faults only and didnot take in consideration the electromechanical trip.where the breaker fail will be detected by current and breaker position (after the initiation from any trip)so the electromechanical trip will not be covered by this setting.

please advice me with the suitable setting current and inform me if this setting ok or not.in addition can i set the current element at the half load or less(100 or 150 A primary)

BEST REGARDS

Eng.AbdElaziz Taman

Egypt,Nubaria Power Station

jhonson is right. set the trip to start your breaker failure function. Then set the timer at 0.5 to 1s before the trip for the breaker failure function to send trip if: - fault is still present - Circuit breaker position is not open - there is a breaker failure function start

AbdElaziz Taman,

The BF condition can be confirmed either by verifying the current flow or by "CB close" status at the end of set time delay. While the current flow based verification is good enough for most of the electrical faults, it is not helpful when it comes to electromechanical relay trips. Hence, it is necessary to choose CB status contact for verification instead of current check. Some of the relays provide option of "CB close or current flow" which is superior.

Further, in case of generator feeders, it is a practice to keep the current threshold to 5% of CT nominal so that the protection can be effective even for electromechanical type trips.

Trust the above is helpful.

1st Stage 150 ms.... for own CB's second trip circuit

2nd Stage 300 ms.... for all CBs' second trip circuit

may it be easy...