Transformer and Reactor Protection

This chapter describes the protection of a class of shunt-connected devices that are important components in any power system. In addition to transformers, it also describes the protection of regulating transformers, shunt reactors, and static var compensators (SVCs). The SVC includes a power transformer as an integral part of the system but also includes inductances, capacitors, or both connected to the secondary side of the transformer bank where the secondary currents are controlled by solid-state switching. For convenience in analysis, the chapter aims to divide the faults associated with transformers into two classes: external faults and internal faults. The chapter considers the line and transformer system where the protection consists of separate relays for the line and for the transformer. Regulating transformers are designed to provide a controllable change in the power system voltage angle, voltage magnitude, or both.