instantaneous setting of medium voltage motor
instantaneous setting of medium voltage motor
(OP)
I am doing a MV motor protection setting. But the Asymetrical inrush current is overlapped with SR469 Inst. setting, if if shift Inst a bit above, like 0.06s, which is still below Cirucir breaker openning time.Then they would be co-ordinated.Is it reliable to do so?






RE: instantaneous setting of medium voltage motor
It is not enough to drag lines around on a TCC. You need to understand how the relay operates.
I don't understand the question about the breaker operating time. The breaker operating time must be added to the relay operate time to determine clearing time.
RE: instantaneous setting of medium voltage motor
CB opening time: 0.08s
Relay overtravel: 0.10s
Safety factor for CT saturation: 0.22s
RE: instantaneous setting of medium voltage motor
I guess do whatever you think is correct.
RE: instantaneous setting of medium voltage motor
RE: instantaneous setting of medium voltage motor
A 0.25 sec breaker clearing time is fairly unusual.
There are a lot of good references, freely available on the Web, that cover relay coordination. You obviously have Internet access, so I'd recommend that you spend a little time doing your own research and problem solving. And since you appear to be doing this for a living, maybe invest in some reference books (and then read those too.)
Good luck.
RE: instantaneous setting of medium voltage motor
With the electromechanical relays there were two approaches in IEEE standards:
1 - Set instantaneous just above 1.73*LRC as recommended by IEEE. Allows for dc component.
OR
2 - Two different instantaneous relay functions. One is set up above 1.73*LRC... maybe even 2.0*LRC. It has no time delay. The other is set around 1.2*LRC. It has a time delay of 100 milliseconds. (GE High Dropout function)
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RE: instantaneous setting of medium voltage motor