Identification of fault and load increase to prevent distance relay mal-operation / Faten Hamima Ismail

Zone 3 distance relay mal-operation due to overloading has been identified as one of the factors of blackouts in the world. One of the causes that lead to this problem is it cannot differentiate between fault occurrence and load increase in transmission lines. Therefore, it is important for us to distinguish between two of the disturbances in order to improve the reliability of distance relay performance. The main objective of this project is to find an indicator that can differentiate between fault occurrence and load increase. This paper presents a proposed method to identify fault occurrence and load increase in transmission line by analyzing instantaneous voltage and root mean square (RMS) voltage signal waveform measured at the remote buses. The proposed technique is designed and validated through simulations of IEEE 9-bus test system in PSCAD. The waveforms of instantaneous voltage as well as RMS voltage measured have been plotted using Microsoft Excel. Analyses of the waveforms have been carried out in order to differentiate the characteristics between two of the disturbances. The results show that there are different characteristic of voltage waveform that can clearly indicates fault occurrence and load increase. The difference between two of them can be identified as fast as in time of one cycle after the occurrence. Therefore, it is suitable to be implemented on Zone 3 distance relay operation because the operation of the zone has time delay in the order of 90 cycles.