ABSTRACT
Transformers in power systems represent large investments and are one of the important components of the power system which must be properly protected depending on their rating and importance. In a radial system, a transformer failure may result in a prolonged shutdown as the downtime for repair of a transformer can be large. Overloads can occur if the downstream protection from the transformer is not properly coordinated. Within their thermal withstand capability, transformers can take short-time overloads. The short circuit in secondary windings when reflected to primary windings can be different depending on winding connections. Differential protections cannot detect low-level interturn faults. Fault-pressure relays and Bucholz protection relays are applied. Surge arresters on primary and secondary windings can be provided. These help to mitigate the magnitude of the surge voltages and transients transferred through the transformer windings through inductive and capacitive couplings.
