Why Over Current Protection is not necessary for modern generators?
Answer: Over Current protection is not considered necessary for modern alternators because these are capable of withstanding a complete short circuit at their terminals for sufficient time without much over heating and damage
What type of protection is provided for the generators against over heating of the generator stator?
Answer: Resistance temperature detector
Which type of relays are used for the Merz-Price protection system for alternator?
Answer: Merz-Price protection is differential protection provided for the alternator. The relays used in the Merz-Price protection system of alternator are instantaneous electro-magnetic type protection
Why large alternator is grounded with large resistance?
Answer: Large capacity of alternators are typically provided with resistance grounding. High value of resistor is connected to the neural path to the ground. If the generator is delta connected, then it is grounded with the help of zig-zag transformer or (Delta-Star) transformer such that a high resistor is connected between the neutral point and the ground. Resistance grounding is provided so as to limit the short circuit current flowing during earth fault to stator winding in order to provide protection against mechanical stresses and melting of winding during Line to Ground short circuit. In large generators fault current is limited as low as 10 to 15 amperes during short circuit.
Answer: Large capacity of alternators are typically provided with resistance grounding. High value of resistor is connected to the neural path to the ground. If the generator is delta connected, then it is grounded with the help of zig-zag transformer or (Delta-Star) transformer such that a high resistor is connected between the neutral point and the ground. Resistance grounding is provided so as to limit the short circuit current flowing during earth fault to stator winding in order to provide protection against mechanical stresses and melting of winding during Line to Ground short circuit. In large generators fault current is limited as low as 10 to 15 amperes during short circuit.
Why it is not necessary to provide protection for turn to turn fault in alternator?
Answer: The coils of the modern alternators are single turn and therefore it is not necessary to provide protection for turn to turn faults
Why it is necessary to suppress field immediately after disconnection of faulty alternator from the system?
Answer: In the event of fault on the generator windings even though the generator circuit breaker is tripped, the fault is continuous to fed as long as the excitation will exist because the emf is induced in the generator. Hence it is necessary to suppress the field immediately after disconnecting the faulty generator from the system
Why it not necessary to provide over-voltage protection in turbo-alternator?
Answer: The over voltage occurs when the prime mover speed increases due to sudden loss of the load on the generator and the speed control governors in case of turbo-generators are very sensitive to the speed variations and therefore generator over voltage of significant duration or magnitude does not generally occur. This is the reason why generators are not provided with over voltage protection
1 comment:
this is a nice post, i am using this generator, got nice information on your post.
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