Application of CT and PT in power system protection
Answers
CT or Current Transformer & PT or Potential Transformer are measuring devices in AC system. These are also called as instrument transformers. As AC system deals with very high power hence we require Ammeter & voltmeter of humongous sizes to measure such high power which is impractical & expensive too.
A CT has following properties:-
It is a step up transformer.
It enhances the voltage & thus the current gets reduced for a fixed power, since P= V×I×cosΦ. Thus for a fixed amount of power, current can easily be measured.
Primary winding of a CT is always connected in series with the load & secondary winding is connected with the ammeter.
A PT has following properties:-
It is step down transformer.
It reduces the voltage for a fixed power & thus the voltage can easily be measured, since P= V×I×cosΦ
The primary winding of the PT is always connected in parallel to the load & secondary winding is connected to the voltmeter.