Evaluation of harmonics impact on digital relays

摘要

Digital relay is an important part of the power system and actually is based on fundamental frequency (50-60 Hz). Digital filter is applied for further processing and performs mathematical operations on sampled values. The digital signal processing (DSP) becomes more applied and used in proactive relays. Obviously, DSP is used in wide range of application (controls, radio, communications and other devices). In this paper the comparison between the conventional digital relay and developed relay using Matlab/Simulink is performed. As known the conventional relay is using mathematics algorithm to calculate the current input signal and to evaluate the fault current, total harmonic distortion (THD) and harmonic components. Likewise, the developed relay is using the current signal and evaluates it and converts the input signal to digital signal. Since the digital signal is more flexible and easier to progress it and work on it. Importantly, the test is used to evaluate the functions and mathematics for both relays.