This paper presents a new approach to real-time fault detection in power transmission systems using Fuzzy Logic (FL) based transmission line distance protection module. The proposed module uses samples of voltage and current signals to calculate line impedance, which used to construct an input-output data.
Simulation studies are preformed and influence of changing system parameters such as fault resistance and fault location. Details of the design procedure and the results of performance studies with the proposed relay are given.
Practical computer simulation program for monitoring the input and calculated values is built based on the Matlab 7.4- Real Time Simulink with National Instruments Data Acquisition System type (NI DAQ-6251). The results show that this approach can be used as an effective tool for high speed digital relaying, a correct detection is achieved in less than 10ms, results performance shows that the proposed algorithm is fast and accurate as compared with others used relays.

Keywords: Transmission line protection, Distance relay, Fuzzy logic, and Matlab-Simulink.