Full load current = 874.77 A 

Minimum fault current which will operate the relay = 174.95 A 

Voltage induced in 15 % winding is 571.58 V 

Earth fault current which 15 % winding will cause = 571.58/r 

This current must be equal to minimum fusing current 174.95 A 

Earthing resistance required = 3.27 ohm 


