Why is power factor of a single-phase induction motor low?

The low power factor of a single-phase induction motor is mainly due to the large magnetizing current which ranges between 60% to 70% of a full-load current. Consequently, even at n0-load, these motor reach temperatures close to the full-load temperature.

source: books of V K Mehta

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What is the most common fault in a power system?

The most common fault in a power system is single-line-to-ground fault. Experience shows that between 70% and 80% of the faults that occur in the power system are single-line-to-ground fault.

source: books of V K Mehta

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What are the advantages of static relay over electromagnetic relay?

Advantages of static relay over electromagnetic relay:

1. Low power consumption as low as 1mW.
2. No moving contacts; hence associated problems of arcing, contact bounce, erosion, replacement of contacts.
3. No gravity effect on operation of static relays. Hence can be used in vessels, i.e., ships, aircrafts etc.
4. A single relay can perform several functions like over current, under voltage, single phasing protection by incorporating respective functional blocks. This is not possible in electromagnetic relays.
5. Static relay is compact.
6. Superior operating characteristics and accuracy.
7. Static relay can think, programmable operation is possible with static relay.
8. Effect of vibration is nil, hence can be used in earthquake-prone areas.
9. Simplified testing and servicing. Can convert even non-electrical quantities to electrical in conjunction with transducers.

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Why busbar protection is needed?

 (a) Fault level at busbar is high

(b) The stability of the system is affected by the faults in the bus zone.

(c) A fault in the bus bar causes interruption of supply to a large portion of the system network.

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What are the main safety devices available with transformer?

Oil level guage, sudden pressure delay, oil temperature indicator, winding temperature indicator .

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