A 50 MVA, 3 phase, 33 kV synchronous generator is protected by the Merz-Price protection using 1000/5 CT's. It is provided with restricted earth fault protection with the earthing resistance of 7.5 ohm. Calculate the percentage of winding unprotected in each phase against earth faults if the minimum operating current of the relay is 0.5 A.
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.
A 50 MVA, 3 phase, 33 kV synchronous generator is protected by the Merz-Price protection using 1000/5 CT's. It is provided with restricted earth fault protection with the earthing resistance of 7.5 ohm. Calculate the percentage of winding unprotected in each phase against earth faults if the minimum operating current of the relay is 0.5 A.
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