Fundamentals of Power System Protection

This chapter aims to provide the reader why power system protection is so important. It examines open‐ and short‐circuit faults, shows different protection zones, explains the operational philosophy of primary and backup relays, lists the design criteria that should be considered during designing protection schemes, introduces overcurrent relays with their types and sub‐types, and covers some case studies. Any electric power system consists of three principal parts: power generation, power transmission, and power distribution. In order to make protection designs adequate, power systems are divided into multiple zones where each zone can be individually protected against its corresponding faults. Good protection system designs can be created if each zone has a number of primary and backup relays. The designed protection scheme can be accomplished in several ways with different complexities and options. Fuses can be considered as the oldest protective devices that are used nowadays.