A30 MW, 37.5 MVA 33KV, star connected alternator is protected by a circulating current protective scheme...

A30 MW, 37.5 MVA 33KV, star connected alternator is protected by a circulating current protective scheme using 600/ 1A CTsand (unbiased ) relays set to operate at 10%t of their rated current (IA) .(a)if the earthing resistor is 90% based on the machine's rating ,estimate the %age of the stator winding which is not protected against an earth fault . (b) If it is required to protect 90% of the winding ,estimate the value of the earthing resistor in ohms and percent based on machine rating .( draw the scheme in star and Delta connection ).

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Manojponduru answered 3 weeks ago

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