Motor Protection For Fused Feeders

[nightfox1925]

We have a 2000HP, 4.16kV motor fed from a NEMA class E2 starter consisting of a Fused Disconnect + vacuum contactor and a Multillin 469 relay.

The Multillin relay included all protection to trip the contactor. My initial plan was to set all applicable protection except for the 50 and 87 which we will just send off an alarm or disable them. The reason why is that since the motor starter is protected by fuses, then these relays will not coordinate and the contactor is not suppose to open on a short circuit.

Furthermore, since 4.16kV grounding system is HRG, 50G is not required.

Any comments...

 

[RRaghunath]

nightfox1925,
I think you are right about 50 & 87. Further, you may also not require Undervoltage protection, considering the contactor would be non-latched type (though I don't see any harm even if the protection is set).
Earth fault protection - depends on the available earth fault current in 4.16kV system. If you have CBCT based protection and expected current is about 25A or even more, you may want to set this protection.

 

[lansford]

You can also look at the contactor withstand and fuse clearing time and if needed for upstream coordination, add some time delay to the 50 device.
JIM