Line impedance measurement to improve power systems protection of the Gautrain 25 kV autotransformer traction power supply system

Abstract

Traction power systems are susceptible to service affecting electrical faults or disturbances. These may cause interruptions of the power supply to the trains, affecting systems operations and causing major delays. Therefore, accuracy in fault reporting and fault location is vital in the decision-making processes that will result in shorter outage periods.The evaluation and analysis of traction power protection systems has become vital to improve the system reliability and reduce outages and related costs. Line impedance measurements form an integral part of fault analysis and distance location due to the use of impedance relays in protection systems. This paper shows the importance of conducting impedance measurements in order to improve the accuracy of distance protection relays. In this paper, impedance measurements were conducted and the measured results were compared with the theoretical values. The feeder to earth, catenary to earth and feeder to catenary impedance measurements were conducted and used in the impedance calculations and analysis. The earth resistances for all line sections were also measured. Furthermore, the line impedance measurements were used for the calculation of the compensation for the earth return factor with speci c application in protection settings optimisation for a traction power system. This has helped to improve the accuracy of the protection parameters. The protection settings parameters were revised as a result.