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MCQ's Current Transformer Fundamentals Assessment

Current transformer holds great significance in power systems. They are used for metering and analyzing the electric current in powerhouses, grid stations, industries, control rooms etc. If you think you have a good understanding of Current Transformer Fundamentals, challenge yourself and take the quiz.

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Question 1 of 20

Q.1 A current transformer is used to:

A

Step up current

B

Step down current

C

None of the above

Question 2 of 20

Q.2 The most common application of current transformer is: 

A

It is used for protection purpose

B

It is used for measuring purpose

C

Both

Question 3 of 20

Q.3 In CT, the current entering in the dot at the primary side of the winding:

A

Must exit from the dot at the secondary side

B

Must enter from the dot at the secondary side

C

None of the above

Question 4 of 20

Q.4 In a transformer, current is:

A

Directly proportional to number of turns

B

Inversely proportional to number of turns

C

None of the above

Question 5 of 20

Q.5 Considering primary current is kept constant, if it is required to have a lower current value at secondary side:

A

Number of turns at primary is increased

B

Number of turns at secondary is increased

C

Number of turns at primary is decreased

D

Both (a) & (b)

E

Both (b) & (c)

Question 6 of 20

Q.6 Calculate Primary current (Iₚ), when Iₛ = 2 Amp and Nₛ : Nₚ = 120 : 1.

A

120

B

240

C

60

Question 7 of 20

Q.7 The line current flowing to the ground in a Delta connected CT circuit is always:

A

Ila + Ilb + Ilc

B

Ila - Ilb - Ilc

C

Zero

D

-Ila - Ilb + Ilc

Question 8 of 20

Q.8 Keeping primary current and number of turns at primary constant if we double the number of turns at secondary, the secondary current becomes:

A

double

B

half

C

4 times

D

Remains same

Question 9 of 20

Q.9 In a current transformer, burden is:

A

Load connected at secondary side of transformer

B

Core impedance

C

Leakage impedance

Question 10 of 20

Q.10 During normal operation, a CT secondary can never be left:

A

Short

B

Open

C

None of the above

Question 11 of 20

Q.11 What is the relation of secondary voltage (Vs) and burden voltage (Vb) in a current transformer? 

A

Vs = Vb

B

Vs < Vb

C

Vs > Vb

Question 12 of 20

Q.12 The main requirement for a protection type CT is that it must have:

A

a high saturation point

B

a high accuracy class

C

a large turn ratio

Question 13 of 20

Q.13 The main requirement for a metering type CT is that it must have:

A

a high saturation point

B

a high accuracy

C

a large turn ratio

Question 14 of 20

Q.14 In additive polarity, primary and secondary have a phase shift of 

A

0°

B

180°

C

120°

Question 15 of 20

Q.15 In subtractive polarity, primary and secondary have a phase shift of 

A

0°

B

180°

C

120°

Question 16 of 20

Q.16 What will be the effect on CT, if its secondary terminal is ungrounded? 

A

Secondary end current increases

B

Secondary end voltage rises

C

No effects

Question 17 of 20

Q.17 Which of the following representation shows a protection class C.T:

A

0.2 S

B

5P20

C

0.1

Question 18 of 20

Q.18 Knee point voltage in C.T is defined as voltage beyond which:

A

10 % increase in secondary voltage will cause excitation current to increase by 50%

B

10 % increase in primary voltage will cause excitation current to increase by 50%

C

10 % increase in secondary voltage will cause secondary current to increase by 50%

Question 19 of 20

Q.19 In order to check the polarity of a CT, which test can be performed?

A

AC test

B

DC test

C

Current method

D

Phase angle method

E

All of the above

Question 20 of 20

Q.20 The magnetization impedance (Ze) is a ___________ quantity and is directly proportional to the ________________.

A

Linear, secondary current

B

Non-linear, secondary voltage

C

Linear, secondary voltage

D

Non-linear, secondary current

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