Directional Comparison Bus Protection Using Partial Operating Current Characteristics

Various bus directional protection methods including widely used superimposed directional element method need to have both voltages and currents from all feeders connected to the zone of protection to find the direction of current for detecting a bus fault or a line fault. This paper presents a new technique for bus directional protection to detect a bus fault. The new technique, which is implementing superimposed directional element method to modify partial operating current characteristics (POC) method, does not use voltages from feeders, hence capacitor voltage transformers (CVTs) are no longer needed in the zone of protection. POC method needs to exclude load terminal current to detect fault during high impedance fault but the proposed technique does not need to exclude such currents. The proposed technique was implemented and tested using different fault cases including CT saturation and high impedance faults. The results show that the proposed technique is successful to detect bus faults with high accuracy and high speed.