Fault detection of a series compensated line during the damping process of Inter-area mode of oscillation

The presence of supplementary controllers for thyristor controlled series compensators (TCSC), to damp the Inter-area power system oscillations makes the resultant transmission line (T.L), reactance varying during the damping process. This variation causes an undesirable effect on the distance relay DR, as its setting depends on the physical impedance of the T.L. In this paper, a novel algorithm is designed for the DR to allow it to update its impedance setting smoothly based on the measured level of series compensation. This adaptive setting allows the DR to detect the correct zone for the low current faults. PSCAD software is used to simulate the tuneable zones setting of the DR during the damping process.