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. Although failure of a protective relay system may have severe local or regional impacts, most protective relay systems are not required to operate to prove they are in working order. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions. It covers standard codes, wiring practices, and norms for protecting generators, transformers, and lines, and provides detailed. These intelligent devices protect the power system by reliably and selectively detecting faults and isolating them fast enough to prevent catastrophic damage. However, simply installing these devices is not enough. To support resilient power-system operation, power system operators must implement a. This document supplements PJM Manual 07 which contains the minimum design standards and requirements for the protection systems associated with the bulk power facilities within PJM. This document provides recommendations, background and philosophy on relay protection that is not available in M07.