Overcurrent Relay Using Voltage Control

Overcurrent relay is the most important and widely used relay in the entire power system (i.e. Transmission system, Generation System, Distribution system) to safe guard power system equipment from the undesirable faults and overloading. These types of relay must have system-oriented setting and must be accurately set according to the requirements. In case of wrong setting, relay will definitely go for false tripping and even bypass fault and that is undesirable to system. So, it is important to validate the setting of protection equipment and confirm its performance when system subject to different types of fault. There are different types of overcurrent relay such as very inverse relay, Definite-time relay, and Inverse-time relay. The purpose of this paper is to model, simulate and evaluate overcurrent relay using voltage control with the help of MATLAB (Simulink) software. Given system is introduced to different types of fault such as L-L, L-L-G, L-G, L-L-L, and L-L-L-G. This paper will focus on the waveforms under different conditions and also the delay characteristics. Overcurrent and Earth-fault do not provide satisfactory protection against internal faults and thus are used to protect the generator against external faults. 51-V relay is used as a back-up protection for overcurrent relay at generating station.