earth fault

Do you know what the trip curve characteristics of your upstream protection (circuit breaker, fuse, vacuum bottle, etc) are? Do you know the expected earth fault current? How about definite time delay?

If you do not know what I am talking about then you should consult a professional protection engineer or electrical consultant. In most cases you really need to make sure you get the right settings, as close-enough general-idea rule-of-thumb settings that could be posted here will probably NOT be good enough to protect the equipment or the public.

Please supply more information. If this is for the transmission network then go and talk to professionals that you SHOULD be getting to do this sort of thing.

Not sure if it is a ground fault interruptor you refer to, but it seems so .

The load would be between the hot line and earth . For human protection, standard value of 5 mA is a norm.

Your local safety authority , or hydro company is likely to have these ratings/values on hand , as they usually have "approval stickers" to go along with their safety inspections.

Do not guess on this whatsoever - it is imperative you inform yourself through your local

safety authority - it is also a liability area should anything go wrong .Be careful .

Chas.