Adaptive distance protection for 110 kV double circuit transmission line

This article approaches the precision of the distance protection relay under earth fault shortcircuits with large resistance on one circuit of a 110 kV double circuit configuration line. Using adaptive trip logic, the reliability and selectivity of the classic distance protection algorithm from a 110 kV double circuit transmission line are improved. In the typical distance protection algorithm to be immune to the influence of the zero sequence mutual impedance and to the high fault resistance, the tilt angle a is calculated and used for changing the position of the fault impedance on the R-X plane. Using only local signals, two current distribution factors are used to calculate the zero sequence current of the healthy parallel circuit and the zero-sequence fault current. In case that the currents of the parallel circuit can be injected into the distance protection relay, the tilt angle a can be estimated with only one current distribution factor. Comprehensive phase to earth shortcircuits with high fault resistance are simulated on one circuit of a 110 kV double configuration transmission line. The shortcircuit scenarios confirm that the distance protection determines an instantaneous trip of the 110 kV circuit breaker of the faulted line, even in the presence of single-phase faults with fault resistance of 50 ohms.