Today all instrumentation system pertaining to industrial process controls as well as domestic application involve automatic fault finding facility. This facility detects the faulty condition of the system and draws operator’s attention towards it enabling him to take suitable remedial action to ensure proper operation of the system. The main purpose of all FDI method is to monitor the system operations and in case of faults accommodate the source of faults so that timely corrective actions are taken.Fault detection and isolation consists basic building blocks that support such systems through the development of fault diagnostic methods, intelligent systems based approaches and sensor based machine monitoring system architecture, embedded and distributed. The protection system relays and auxiliary relays also provided signals to alarm and annunciation system. A set of annunciation windows are provided on control panels for each fault clearing relay with accept, test and reset facility through push buttons. Alarm and trip annunciation indicate the fault and advise operating personnel of the changed operating conditions.