COMPARATIVE STUDY BETWEEN DIFFERENT METHODS USED IN PROTECTION BY DISTANCE OF ELECTRICAL NETWORKS

Distance relays (D.R) are used in protection of electrical networks to measure the apparent impedance of the fault and shall compare it with its D.R setting impedance, but the apparent impedance may be differ from the actual impedance due to the network challenges appeared such as effect of branched networks, series capacitor for compensation, power swing, parallel transmission lines and fault resistance. All of these challenges will result to overreach or underreach errors, accordingly false trip. Some of approach methods shall be introduced in this paper to overcome these errors. In the recent transmission line (T.L) systems, more than one of these challenges can appear simultaneously. It shall be difficult to adjust the D.R with value suitable for all challenges. In this paper, the study how D.R will overcome each challenge alone and how it will be adjusted with value suitable for all of these challenges together shall be considered.