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 specific 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.
Highlights
Ever since the Gautrain project in Johannesburg, South Africa, was commissioned in June 2010, a lot of power system faults have been experienced and efforts have been made to adjust the relay parameters in order to improve the protection system
Without conducting line impedance measurements, the distance protection settings depend on the manual calculations and simulations using conductor data from the manufacturers
The process of analysis and measurements of line and earth impedances was conducted in order to compare with theoretical or calculated values as given by the original equipment manufacturers of the conductors
Summary
Ever since the Gautrain project in Johannesburg, South Africa, was commissioned in June 2010, a lot of power system faults have been experienced and efforts have been made to adjust the relay parameters in order to improve the protection system. Each end is connected to a tensioning weight whose prime purpose is to restrict the sag and elongation due to temperature variations This arrangement of the catenary system as described in this paragraph makes it complicated to obtain correct impedances from the conductor specifications and apply them as a function of distance without conducting measurements, as is often the case with power transmission lines. The other benefit of conducting line impedance measurements is the ability to use the results for the calculation of the compensation for the earth return factor for protection settings optimisation. This factor has been identified as a contributing factor to the accuracy of the impedance settings [4].
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