The most important of these are: transmission and distribution lines emanating from the station, step-up and step-down transformers, station buses, breakers, shunt and series reactors and shunt and series capacitors. Engineering use: Relays are used on feeders, transformers, buses, motors, generators, and transmission lines to protect equipment and improve system reliability. What controls it: Relay performance depends on the protected zone, CT/PT inputs, pickup settings, time delay, breaker clearing time, trip. This handbook covers the code of practice in protection circuitry including standard lead and device numbers, mode of connections at terminal strips, colour codes in multicore cables, dos and donts in execution. Also principles of various protective relays and schemes including special protection. presentation of protection and control relaying. They are activated by means which are not dependent on a continual AC supply.
[PDF Version]