Voltage or Potential Transformer
Q. State the specifications of PT as a protective transformer.
- Voltage transformers (potential transformers) are used for measurement and protection.
- They may be either single phase or three phase units.
- Voltage transformers are necessary for voltage, directional, distance protection.
- Primary of voltage transformer is connected to power circuit between phase and ground.
- The volt-ampere rating of voltage transformers is S smaller as compared with that of power transformer.
- There are two types of construction
– Electromagnetic potential transformer in which primary and secondary are wound on magnetic core like in usual transform.
– Capacitor potential transformer in which the primary voltage is applied to a series capacitor group. The voltage across one of the capacitor is taken to auxiliary voltage transformer. The secondary of auxiliary voltage transformer is taken for measurement or protection.
– CVT combines function of coupling capacitor and VT.