The neutral point of 25 MVA, 11KV alternator is grounded through a resistance of 5 Ω, the relay is set to operate when there is an out of balance current of 2A. The CTs used have a ratio of 1000/5. Calculate ( neglect reactance of alternator ): 1) the percentage of stator winding protected against an earth fault. 2) the minimum value of earthing resistance to protect 95% of the winding.
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 25 MVA, 11KV alternator is grounded through a resistance of 5 Ω, the relay is set to operate when there is an out of balance current of 2A. The CTs used have a ratio of 1000/5. Calculate ( neglect reactance of alternator ):
1) the percentage of stator winding protected against an earth fault.
2) the minimum value of earthing resistance to protect 95% of the winding.
Trending now
This is a popular solution!
Step by step
Solved in 4 steps
