IDMT Relay Protection Settings

[viking684]

Hello,

I am an engineering student interning at a Utility company and would like some help understanding relay characteristics for protection settings. I was wondering if someone could explain what all this means and if the feeder relay setting is correct. Any assistance is greatly appreciated.

51 P: Extremely Inverse
51 P: Pick up = 4.6
51 P: Time Dial = 2.0
50 P-1: Standard
50 P-1: Pick up x 4.0
51 N: Extremely Inverse
51 N: Pick up = 1.3
51 N: Time Dial = 1.8
50 N-1: Standard
50 N-1: Pick up x 5.9
Phase CT ratio: 60
Ground CT ratio: 60
VT ratio: 132

Thanks!

 

[dpc]

I think you're going to put in at least a little effort before anyone is going to spend any time on this. Any standard text on protective relaying would be a good start and then a review of the instruction book for the particular relay.

Just a listing of relay settings without a one-line diagram is not sufficient for anyone to tell if the settings are correct.

 

[davidbeach]

Starting with the correctness question first - That is impossible for anybody outside your organization to know and even there there may be no one right answer.

51 P: Extremely Inverse - Curve type for phase time overcurrent
51 P: Pick up = 4.6 - pick up point, in secondary amps
51 P: Time Dial = 2.0 - determines how long it takes to time out
50 P-1: Standard - something about the instantaneous
50 P-1: Pick up x 4.0 - instantaneous set at 4.6 * 4 amps secondary
51 N: Extremely Inverse - ground, similar to phase
51 N: Pick up = 1.3 - ground, similar to phase
51 N: Time Dial = 1.8 - ground, similar to phase
50 N-1: Standard - ground, similar to phase
50 N-1: Pick up x 5.9 - ground, similar to phase
Phase CT ratio: 60 - probably a 300:5 CT, possibly, but unlikely, a 60:1 CT
Ground CT ratio: 60 - same, probably the same CTs
VT ratio: 132 - primary voltage is 132 times what goes to the relay.

 

[dpc]

David is in a generous mood today....

 

[davidbeach]

Free wine at an Embassy Suites Manager's reception on the other side of the country does that every now and then. ;-)

 

[viking684]

Thanks Dave!

dpc- I am currently compiling all the data, like system impedance, etc. I have a single line diagram, but dont think I can post it. I just didnt understand the relay settings, which Dave eloquently provided.

 

[davidbeach]

dpc might be Dave, but I'm not.

 

[dpc]

Happy Hour must be over...