Performance of impedance measurement algorithm applied in line with a compensation circuit

This paper describes a performance of impedance measurement algorithms of SEL-421 distance relay protection when applied to protect series compensated line during fault conditions. The Performance is carried out by varying the value of uncertainty parameters to the accuracy of the impedance measurement algorithm of the relay for the simulated faults, which is measured from the located relay to the fault points. Experiments were carried out with a combination of DIgSILENT PowerFactory software to model and simulate electrical power protection systems with a system voltage of 400 kV and a line length of 300 km with compensation circuit placed in the middle of a protected transmission line. For a fault simulated 0.45 p. U in front of compensation circuit, the relay still works correctly. However, there will be an operation failure of the relay for the fault simulated at 0.8 p. U behind compensation circuit. Faults simulation and performances are performed automatically through the algorithm developed using the DIgSILENT Program Language (DPL). From the enclosed results, the developed method is applicable for testing the performance of the IEDs algorithm. (paper)