Current Transformer MCQ Questions with Answers

A current transformer is a type of instrumentation transformer that steps down current in power systems to safe levels that can be processed via relays and measurement devices/equipment. Current transformers can be found in generation stations and switching stations.

Given below are the most important Current Transformer MCQ Questions

Current Transformers are used for

Current Transformers are used for:

  1. Measurement purposes
  2. Instrumentation
  3. Protection
  4. All of the above

Correct answer: 4. All of the above

A current transformer plays the measurement, instrumentation as well as protection roles in power systems.

Secondary winding rating of Current Transformer

Current transformers usually have a secondary winding rating of:

  1. 5 A
  2. 20 A
  3. 50 A
  4. 100 A

Correct answer: 1. 5 A

Secondary circuit of Current transformer should never become

Secondary circuit of Current transformer should never become:

  1. Open circuited
  2. Short circuited
  3. Any of these

Correct answer: 1. Open circuited

Explanation: Complete explanation for CT secondary closure

Selector switches used for CT should be of which type

Selector switches used for CT should be of which type:

  1. Make before break
  2. DPDT
  3. Low impedance
  4. None of these

Correct answer: 1. Make before break

Explanation: The selector switches used for CT should be of Make before break type so that CT never becomes open-circuited.

Primary Terminals of CT are marked using letters

Primary Terminals of CT are marked using letters:

  1. X1 and X2
  2. H1 and H2
  3. P1 and Q1
  4. P1 and U1

Correct answer: 2. H1 and H2

Secondary Terminals of CT are marked using letters

Secondary Terminals of CT are marked using letters:

  1. X1 and X2
  2. H1 and H2
  3. P1 and Q1
  4. P1 and U1

Correct answer: 1. X1 and X2

Current transformer with rated secondary current of 5 A and Rating factor 4.0 RF can hold secondary current of

Current transformer with rated secondary current of 5 A and Rating factor 4.0 RF can hold secondary current of:

  1. 4 A
  2. 5 A
  3. 10 A
  4. 20 A

Correct answer: 4. 20 A

Rating factor of CT indicates maximum current that can flow through a CT without exceeding the thermal capability of its windings

Cast Resin type Current Transformer is recommended for

Cast Resin type Current Transformer is recommended for:

  1. Indoor use
  2. Outdoor use

Correct answer: 2. Outdoor use

Generally cast resin type transformers are recommended for outdoor use.

Turns ratio of current transformers

Current transformers (CTs) have turns ratios:

  1. Greater than one
  2. Lesser than one
  3. Equal to one
  4. None of the above

Correct answer: 2. Lesser than one

Current transformers have turns ratios less than one.

What happens if the secondary of a current transformer is open-circuited

What happens if the secondary of a current transformer is open-circuited:

  1. A decrement in an overall efficiency of the metering circuit occurs
  2. Dangerously high voltages can develop
  3. Wrong values of output
  4. Nothing happens

Correct answer: 2. Dangerously high voltages can develop

If the secondary of a current transformer is open-circuited dangerously high voltages can develop. So the secondary of a current transformer should never be open circuited.

So that was all about the Current Transformer MCQ Questions.

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