Difference between Current transformer and Potential transformer

Current transformer and Potential transformer are the types of instrument transformer. An instrument transformer is a special type of transformer that is used in the measurement of high voltage and high current, not allowing measuring instruments to come in direct contact with high voltage circuits. Potential transformer is also known as voltage transformer. In this article, we will see what are the differences between current and potential transformers.

The main difference between current transformer and potential transformer is that a current transformer is used for the measurement of high currents whereas a potential transformer is used for the measurement of high voltages. Both transformers are used for extending the range of the measuring instruments. A current transformer is used for extending the range of an ammeter whereas a potential transformer is used for extending the range of a voltmeter.

Let see the basic differences between the two in detail.

Difference between Current Transformer and Potential Transformer in tabular form

Current Transformer Potential Transformer
It is generally abbreviated as CT. It is generally abbreviated as PT.
It is connected in series with the power circuit. It is connected in parallel with the power circuit.
Its secondary is connected to an Ammeter. Its secondary is connected to a Voltmeter.
Its secondary work always in short circuit condition. Its secondary work always in open circuit condition.
The current transformer’s primary current depends on power circuit current. The potential transformer’s primary current depends on the secondary burden.
The current transformer’s primary current and excitation vary over a wide range with the change of power circuit current. The potential transformer’s primary current and excitation are restricted to a small range.
In this transformer, one terminal of the secondary is earthed to avoid the insulation breakdown. In this transformer, one terminal of secondary can be earthed for safety.
Its secondary never be open-circuited under operation. Its secondary can be open under operation.

Conclusion

A current transformer (CT) is connected in series with the power circuit whereas a potential transformer (PT) is connected in parallel with the power circuit. A CT can never be open-circuited when it is in operation whereas a PT can be open under working conditions.

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