AC PRO Trip units.
AC PRO Trip units.
(OP)
After combing through the manual I still can't determing how this unit differentiates a Ground Fault from a Long Time, Short Time, or Instantaneous Fault. They are installed on a 480 Wye three wire secondary.
After playing around with the tripping time calculator on the Utility Relay Company website, It seems like there is no difference. Just different names for different curves.
If this is the case, it seems that the GF setting would have to be set higher than all others, or the unit would always trip on GF.
After playing around with the tripping time calculator on the Utility Relay Company website, It seems like there is no difference. Just different names for different curves.
If this is the case, it seems that the GF setting would have to be set higher than all others, or the unit would always trip on GF.






RE: AC PRO Trip units.
RE: AC PRO Trip units.
Another problem with the coordination is that the main breaker uses a GE IAC instantaneous relay hooked up to a GF CT. This causes it to pick up before any of the other downstream breakers. We can't really change this setup, because some of these breakers feed large MV motors and also 480V load centers. If we were to raise the pick up current, of increase the delay, we would be losing some of our protection for the motors.
I'm trying to get a understanding of all of our protection schemes since I'm new to this plant.
RE: AC PRO Trip units.
RE: AC PRO Trip units.
As for the sum of the vectors explanation, I found it on the first page of the insruction manual. I had went through that manual several times, but neglected to read the first paragraph, oh well. Thanks for the explanation though.