The neutral point of a 11 kV alternator is earthed through a resistance of 12 ohm. the relay is set to operate when there is out of balance current of 0.8 A. The CTs have a ratio of 200/5. What percentage of the winding is protected against earth faults. What must be the minimum value of earthing resistance required to give 90% of protection to each phase.?
Synchronous Generator
In comparison to an asynchronous generator, it is a machine where the rotor speed is equal to the rotating magnetic field produced by the stator, i.e., mechanical speed is equal to the electrical speed, thus called synchronous, and not asynchronous.
Salient Pole Rotor
Salient pole rotor includes a large number of exposed poles mounted on a magnetic wheel. The construction of a bright pole is as shown in the image on the left. The proposed poles are made of metal laminations. The rotor winding is provided on these poles and is supported by pole shoes.
The neutral point of a 11 kV alternator is earthed through a resistance of 12 ohm. the relay is set to operate when there is out of balance current of 0.8 A. The CTs have a ratio of 200/5. What percentage of the winding is protected against earth faults. What must be the minimum value of earthing resistance required to give 90% of protection to each phase.?
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