Protection relay misconfiguration refers to incorrect setup of relay parameters that causes the device to operate outside its intended protection logic. Unlike hardware failure, the relay remains functional, but its decision-making is wrong. However, in many real-world plants, failures are not caused by relay hardware itself but by incorrect configuration, outdated settings. 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. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions.