- If the CT is under service the secondary of a C.T cannot be open circuited on any condition.
- The CT can be regarded as a series transformer.
- The current in the primary side of a C.T is independent of the secondary also known as the burden.
- The primary winding of the CT is connected in series with the line carrying the current to be measured. Hence it carries out the full line current.
- With the help of CT, a 5A ammeter can be used to measure a high current like 200A.
- The secondary of a P.T can be open circuited without any damage being caused either by the operator or the transformer.
- P.T may be considered as a parallel transformer.
- The primary current of a P.T depends upon the secondary circuit conditions (burden).
- The primary winding P.T is connected across the line of voltage to be measured. Hence the full line voltage is impressed across its terminal.
- With the help of P.T, a 120V voltmeter can be used to measure very high voltages like 11KV.
Source : https://owlcation.com/stem/What-is-a-Current-transformer-How-does-it-work