The correct answer is: C. Potential transformer
A potential transformer (PT) is a type of transformer that is used to step down high voltage to a lower voltage for measurement or control purposes. The secondary winding of a PT is always kept closed to provide a current path for the transformer’s core. This current path helps to reduce the core’s magnetization current, which in turn reduces the transformer’s losses.
A step-up transformer is a type of transformer that is used to increase voltage. The secondary winding of a step-up transformer has more turns than the primary winding. This means that the voltage on the secondary winding is higher than the voltage on the primary winding.
A step-down transformer is a type of transformer that is used to decrease voltage. The secondary winding of a step-down transformer has fewer turns than the primary winding. This means that the voltage on the secondary winding is lower than the voltage on the primary winding.
A current transformer (CT) is a type of transformer that is used to measure current. The secondary winding of a CT has a much higher number of turns than the primary winding. This means that the current on the secondary winding is much lower than the current on the primary winding. The low current on the secondary winding can then be easily measured by a current meter.