IEC 60255-1:2022 specifies common rules and requirements applicable to measuring relays and protection equipment, including any combination of equipment to form a distributed protection scheme for power system protection such as control, monitoring and process interface equipment . IEC 60255-1:2022 specifies common rules and requirements applicable to measuring relays and protection equipment, including any combination of equipment to form a distributed protection scheme for power system protection such as control, monitoring and process interface equipment . 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. This happens because the main function of protection devices is related to operation under fault conditions so these devices cannot be tested under normal operating conditions. This international standard outlines the requirements for measuring, testing, and verifying protective relays. Without. THEY SHOULD BE GIVEN FIRST LINE MAINTENANCE ATTENTION. ” relay may only need to operate for 0. But failure to operate as intended can result in extensive damage, extended power outages, and loss of life.