Field failure Of Generator

[shkim2000]

I set the following figures for field protection(40)
Alarm angle : 15 degree
(Alarm)
Xa1 : 3 Ohm
Xb1 : 44.8 Ohm
Time Dealy : 7 s
(Trip)
Xa2 : 2 Ohm
Xb2 : 16.8Ohm
Time Delay : 0s
In these settings, I have tripping of ACB for Generator due to field failure. I triy to troubleshooting for it. Can anybody advise what I should check for it ?

 

[alehman]

There is not enough information here to troubleshoot this problem. Are these primary or secondary impedances? We would need to know the basic parameters of the generator (Xd and X'd for starters). Most relays are "offset mho" type that include circle diameter and offset settings. The diameter for fast response is typically set about 1.0pu with an offset of -X'd/2. You should carefully read the relay instruction manual. It typically includes guidance for settings and troubleshooting.

The 0 time delay on trip jumps out at me. Normally this would be a few tenths of a second or more.

If you suspect an actual loss of excitation, check the field current and output power factor.