Improved Fault-Location System for Railway Distribution System Using Superimposed Signal

The railway distribution system is a neutral noneffectively grounded medium-voltage network. An advanced fault-location system for this distribution network, called the railway distribution network fault location system, is proposed in this paper. This fault-location system is based on tracing the superimposed signal and the work principle, simulation results, and field tests of the location system are presented. It is able to identify the fault location in a fast and accurate way. Compared with other conventional superimposed signal-based schemes, the system's performance is improved by employing the inject and fault-current detect sensor (IFCDS) to trace the fault signal and wireless to transmit detect information. The IFCDS, which permanently hangs on feeders, is based on the wireless sensor networks technology, so it can network automatically in a certain range, and improve the flexibility of the communication subsystem. Through analyzing the uploaded information by the fault-location computer in the substation, the fault point can be located. Issues of superimposed signals, such as optimal frequency choice, impact of tapped load, fault distance, and fault resistance, and so on are of concern. Through simulation in PSCAD/EMTDC, these issues are fully discussed. At last, the tests in the field show that the system has simple principle, high reliability, fast location speed (usually less than 15 min), and high accuracy (location error is less than 0.5 km).