Types of Protective Relays: Protective relays are categorized by their mechanism (electromagnetic, static, mechanical) and function (time-based, current, voltage). There are various types of Relay Classification in Power System Protection. Normally the actuating quantity is an electrical signal, although sometimes the actuating quantity may be pressure or temperature. : 4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as. 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. Selectivity is a mandatory requirement for all protection, but the importance of it depends on the application.
