Ground Fault and protection scheme
Ground Fault and protection scheme
(OP)
When coordinating the main feeder ground fault protection with downstream fuses, does the kind of protection scheme matters?
If it is Residual connection or core balance or calculated?
My feeder ground detection is calculated based on Ia+Ib+IC value, do I need to coordinate the ground curve with fuses downstream?
If it is Residual connection or core balance or calculated?
My feeder ground detection is calculated based on Ia+Ib+IC value, do I need to coordinate the ground curve with fuses downstream?






RE: Ground Fault and protection scheme
If you do, your clearing times will be much greater.
If you don't, you risk having a ground fault beyond the fuses, and clearing it with your main.
Which is a bigger problem on your system?
RE: Ground Fault and protection scheme
What do you mean by "If you do, your clearing times will be much greater"?
I was always under impression that when coordination study is done, phase current protection curves will be coordinated with downstream fuses or relays, does this mean that ground curves also need to be coordinated with downstream fuses and relays?
Ground curves have lower setting, how this could be achieved?
RE: Ground Fault and protection scheme
RE: Ground Fault and protection scheme
Although, GF has definite time delay, which helps eliminate most nuisance trips of the main. History and experience has shown that it is generally acceptable (and hence the codes are the way they are, in the USA).
Having said that, one should consider providing multiple levels of GFP when discrimination is very critical.
Rafiq Bulsara
http://www.srengineersct.com
RE: Ground Fault and protection scheme
Provided your possible zero sequence unbalance allows it.
RE: Ground Fault and protection scheme