• If the earthing transformer on the Delta Side is outsides the Zone of protection the Earth Fault(E/F)in the delta system outside Current Transformer(CT) locations would produce current distributions as shown which circulate within the differential CT secondary and is kept out of operating coils.



  • Zig-Zag or inter connected star grounding transformer has normal magnetizing impedance of high value but for E/F, currents flow in windings of the same - core in such a manner that the ampere turn cancel and hence offer lower impedance.