How 100% winding protection is given there?

How 100% winding protection is given there? 
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1 Answer

Answer :

a) Inject sub harmonic AC current into generator neutral. Monitor its amplitude. E/F impedance reduces so current drawn increases and trips (Not used). 

b) 3rd harmonic voltage monitored on neutral, fault near neutral upto 25% winding. 3rd harmonic voltage reduces to zero. Above this 3rd harmonic voltage increases, so combined both 3rd harmonic and zero sequence relays for 100% covering, no blind zone.
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