Abstract: The alternator is the main part of any power system which provides power to the grid system which used as emergency power supply using prime-mover, as it is very costly, necessary to protect it from different faults and abnormal conditions. This report contains the alternator protection matlab simulation and demo panel. In demo panel contains five faults such as phase to phase, short circuit, over voltage, under voltage, overloading and loss of excitation occurred in alternator. If generator is not protected then power system may get collapse. A comprehensive and transient simulation model is established for various faults. All of faults in stator windings including internal faults and ground fault can be simulated in this unified model. Using the model to study the variation of current and voltage is conductive to analyse the features of fault and design the protection scheme. It is shown that the model accurately predicts the voltage and current waveforms under fault conditions. Hence it used to analyse important features of faults and to design appropriate protection schemes. The internal and external faults can result in a damage caused by the heavy transient short-circuit current. Compared with the internal and external faults, the ground fault is slight destructive but it will extend to the internal short-circuit faults in long running. The protection of the ground fault sensitively and correctly operates can reduce the probability of those severe faults occurring. So it is very important for relay protection of generator to correctly analyse the characteristics of these faults of windings using matlab simulation.

Keywords: Alternator Protection, Simulation Model, Internal and External Fault.