Restricted Earth Fault

[Cerkit]

Hi,

For a restricted earth fault relay with an effective setting of 0.2A. The CT ratio is 2000:1 and the maximum earth fault current is 800A through an earthing transformer. If there is an earth fault at the end of an LV winding (so covers the entire winding) is it correct that the primary current in the neutral required to operate the relay will be 400A? I calculated this from

0.2A (setting) * 2000 (CT ratio) = 400A

As the full winding is included then I multiply by 1, 400A * 1 = 400A

Thanks

 

[Kiribanda]

Cerkit,
It looks like,
1) your distribution is DELTA and you have put a 800A zig zag earthing transformer for
earth fault protection.
2) The NCT installed at the neutral to earth path of the zig zag earthing transformer
is 2000/1.
If that is the case, in my opinion the relay scheme is not a REF (87G) but a simple
over current (50/51N) protection for earth fault.
Based on above the setting 400A is correct for me.