Improved Fault-Location System for Railway Distribution System Using Superimposed Signal
ABSTRACT 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).
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ABSTRACT: The grounding of AC and DC motor drive systems should detect and clear ground faults both on the source and load side of the power converters. Most drive systems are separately derived through a step-down transformer, which serves as a drive isolation, as well as rectifier transformer. Isolation transformers on individual or group drive systems, downstream of main substation transformers are also common. An output isolation transformer on an AC drive will isolate the drive electronics, step up the AC voltage from the inverter section and also serve to control high line-to-ground voltages on the motor windings. The grounding system has a profound effect upon the continuity of operations, loading of the solid-state devices and common-mode voltages. This paper discusses the various possibilities of grounding of low-voltage and medium-voltage motor drive systems and shows that a high-resistance grounding system can be often implemented to permit continuity of operations, allow fault detection and limit the transient overvoltageIEEE Transactions on Industry Applications 02/1998; · 1.67 Impact Factor
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ABSTRACT: One of the most compelling technological advances of this decade has been the advent of deploying wireless networks of heterogeneous smart sensor nodes for complex information gathering tasks. A wireless distributed sensor network (DSN) is a self-organizing , ad-hoc network of a large number of cooperative intelligent sensor nodes. Due to the limited power of sensor nodes, energy-efficient DSN are essentially multi-hop networks. The self-organizing capabilities, and the cooperative operation of DSN allow for forming reliable clusters of sensors deployed near, or at, the sites of target phenomena. Reliable monitoring of a phenomenon (or event detection) depends on the collective data provided by the target cluster of sensors, and not on any individual node. The failure of one or more nodes may not cause the operational data sources to be disconnected from the data sinks (command nodes or end user stations). However, it may increase the number of hops a data message has to go through before reaching its destination (and subsequently increase the message delay). In this paper, we focus on two related problems: computing a measure for the reliability of DSN, and computing a measure for the expected & the maximum message delay between data sources (sensors) & data sinks in an operational DSN. Given an estimation of the failure probabilities of the sensors, as well as the intermediate nodes (nodes used to relay messages between data sources, and data sinks), we use a probabilistic graph to model DSN. We define the DSN reliability as the probability that there exists an operating communication path between the sink node, and at least one operational sensor in a target cluster. We show that both problems are #P-hard for arbitrary networks. We then present two algorithms for computing the reliability, and the expected message delay for arbitrary networks. We also consider two special cases where efficient (polynomial time) algorithms are developed. Finally, we present some numerical results that demonstrate some of the applications of our algorithms.IEEE Transactions on Reliability 04/2005; · 2.29 Impact Factor
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ABSTRACT: One of the most common and difficult problems to solve in industrial power systems is the location and elimination of the ground fault. Ground faults that occur in ungrounded and high-resistance grounded systems do not draw enough current to trigger circuit breaker or fuse operation, making them difficult to localize. Techniques currently used to track down faults are time consuming and cumbersome. A new approach developed for ground-fault localization on ungrounded and high-resistance grounded low-voltage systems is described. The system consists of a novel ground-fault relay that operates in conjunction with low-cost fault indicators permanently mounted in the circuit. The ground-fault relay employs digital signal processing techniques to detect the fault, identify the faulted phase, and measure the electrical distance away from the substation. The remote fault indicators are used to visually indicate where the fault is located. The resulting system provides a fast, easy, economical, and safe detection system for ground-fault localizationIEEE Transactions on Industry Applications 08/2001; 37(4):1152-1159. · 1.67 Impact Factor