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 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.

Fault Analysis of the Gautrain 2 × 25 kV AC Traction Power Supply System Using Disturbance Fault Records and On-Site Testing

“…The disturbance records contain such information as types of fault, current and voltage magnitudes, fault duration, and in some cases fault location [5], [12]- [13]. In order for distance protection relays to operate accurately, they need accurate system parameters, suitable philosophies and accurate relay settings that are applicable to the type of power system being protected [6], [14]- [15]. Other authors explain why it is complicated to identify the fault location of a 2 × 25 kV traction system due to its non-linear impedance value when measured as a function of distance [15]- [17].…”

“…Traction lines differ from high voltage or medium voltage transmission lines in their configuration and equipment or components that make up the OHW, the types of feeding transformers used in the substations and protection systems. For example, the traction system has the earth return circuit, neutral sections, section insulators, crossovers, weight tensioning devices, feeder wires, and contact/catenary wire combination interconnected through wire droppers hanging between the catenary and contact wire [6], [20]- [23]. There are also differences in impedances, train pantograph/OHW interaction and different power systems protection philosophies [6].…”

“…For example, the traction system has the earth return circuit, neutral sections, section insulators, crossovers, weight tensioning devices, feeder wires, and contact/catenary wire combination interconnected through wire droppers hanging between the catenary and contact wire [6], [20]- [23]. There are also differences in impedances, train pantograph/OHW interaction and different power systems protection philosophies [6]. The autotransformer feeding system described in other systems [21], [24] contains sectioning post and parallel post locations.…”

“…For the purposes of this study, specialized test equipment was connected to relay panels and test blocks connected to current transformers (CTs) and voltage transformers (VTs) at the substations at both ends of existing OHW line sections and different types of faults were simulated. The tests are done relative to measured impedances, system parameters and applied protection settings for the line sections under evaluation [6]. The results obtained from these tests including fault types and operating performances are analyzed.…”

Innovative Integrated Solution for Monitoring and Protection of Power Supply System from Railway Infrastructure

“…In this sense, some research papers describe some new methods to measure the line impedance in order to improve distance protection relays, in the sense of quick location of a fault, for improving the continuity and reliability of the railway infrastructure [ 13 , 14 , 15 , 16 ]. Furthermore, Cho et al [ 13 ] present a fault locator used to detect the fault location with good accuracy.…”