TRANSFORMERS QUIZ

For which of the following protection from negative sequence currents is provided ?

Generators

Transformers

Transmission line

Motors

TRUE ANSWER : ?
YOUR ANSWER : ?

Most of the relays on service on electric power system are

None of these

electro-mechanical relays

thermal relays

electronic relays

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A three phase circuit breaker is rated at 2000 MVA, 33 kv. The symmetrical breaking current is

35 kA

60 kA

80 kA

20 kA

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Current chopping mainly occurs in

vaccum circuit breaker

sf 6 circuit breaker

air-blast circuit breaker

oil circuit breaker

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A circuit breaker must perform the duty of

being closed on to a fault

All of these

opening the faulty circuit and breaking the fault current

carrying fault current for a short time

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The fuse rating is expressed in terms of

voltage

current

kVA

VAR

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In a circuit breaker the time duration from the instant of the fault to extinction of arc is known as

lag time

clearing time

lead time

operation time

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The rate of rise of restriking voltage depends on

the inductance of the system only

the type of circuit breaker

the capacitance of the system only

both inductance and capacitance of the system

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The arcing contacts in a circuit breaker are made of

aluminium alloy

copper tungsten alloy

electrolytic copper

porcelain

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An efficient and a well designed protective relaying should have

good selectivity and reliability

economy and simplicity

All of these

high speed and selectivity

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