Relay coordination

[Charz]

The suppied breaker in the MCC panel is of GE - POWER BREAK-II and the model no: GB108L3XXXFXXXX. However the Engineer selected the breaker GE Entellisys -EGF-08 in ETAP software.

EGF-08 trip unit which has only 4 LT band settings, but trip unit of GE- Power break -II (ICCB) has 19 bands for LT band settings and 11 bands for ST band settings.

My Engineer says, this will not affect anything. Quite apparently, the trip timings are different for the same band settings, but I failed to understand why he says it wont affect anything?

Any inputs?

 

[synchro]

Is there any reason to believe that the EGF-08 can't be set to a pair of ST and LT bands that would meet the protection and coordination requirements of this installation? More resolution and options adds flexibility but usually there's also a cost tradeoff to consider.

 

[topgone]

You don't have to go the high-end way if a low-cost solution can be had. Just you check the TCCs vs damage curves and start from there.