Generator zone of protection 1

[tumbleweed1]

Does the zone of protection for generator overcurrent and/or differential protection protect a fault on the cable from the generator to the next downstream circuit breaker? Say the cable is 100ft max.

 

[dpc]

That depends on the location of the current transformers used to sense current. Maybe post a simplified one-line.

 

[waross]

Differential protection typically uses two CTs per phase and compares the currents. The area between the CTs is protected. One CT may be on the secondary of the unit transformer. If so, the differential relay will be programmed to compensate for this.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[tumbleweed1]

That's what I was thinking DPC. For record, it actually relates back to a previous post of mine and what the purpose of using a fused disconnect following a generator, and then a breaker following the disconnect. He made some mention that the cable from the generator to the breaker would not be protected, however if they had placed the CT on the generator side of the breaker and left out the fused disconnect then the cable would still be protected.

For reference:

Gen-->(current CT placement)fused disconnect-->Cable-->(CT should be placed here)Breaker-->Bus

 

[ScottyUK]

For a differential scheme you'd need another CT at the neutral end of the stator winding. The existing CT location provides overcurrent protection for the cable, but the cable is not within the differential zone, assuming you have the other CT required to define the zone. Your proposed location would achieve the latter.

 

[tumbleweed1]

Yes there are neutral cts as well