Wide-area Current Differential Protection Research Articles

Power supply arm protection scheme of high-speed railway based on wide-area current differential

When fault occurs on cross-coupling autotransformer (AT) power supply traction network, the up-line and down-line feeder circuit breakers in the traction substation trip at the same time without selectivity, which leads to an extended power failure. Based on equivalent circuit and Kirchhoff’s current law, the feeder current characteristic in the substation, AT station and sectioning post when T–R fault, F–R fault, and T–F fault occur are analyzed and their expressions are obtained. When the traction power supply system is equipped with wide-area protection measurement and control system, the feeder protection device in each station collects the feeder currents in other two stations through the wide-area protection channel and a wide-area current differential protection scheme based on the feeder current characteristic is proposed. When a short-circuit fault occurs in the power supply arm, all the feeder protection devices in each station receive the feeder currents with time stamp in other two stations. After data synchronous processing and logic judgment, the fault line of the power supply arm can be identified and isolated quickly. The simulation result based on MATLAB/Simulink shows that the power supply arm protection scheme based on wide-area current differential has good fault discrimination ability under different fault positions, transition resistances, and fault types. The verification of measured data shows that the novel protection scheme will not be affected by the special working conditions of the electrical multiple unit (EMU), and reliability, selectivity, and rapidity of relay protection are all improved.

Improved algorithm of wide‐area current differential protection based on non‐uniform quantisation

Current differential protection characterised by whole-line quick action has now become the main concept in the research of the wide-area relay protection algorithm. However, strict requirements on broadband and real-time capability are difficult to meet in actual projects. Aiming at reducing the system traffic while not compromising the protection performance, the study proposes an improved algorithm of wide-area current differential protection based on non-uniform quantisation. The algorithm is proposed based on the information theory and in view of the non-uniform distribution of information redundancy of current signal in different width intervals. Comparing with traditional current differential protections, the improved algorithm is able to retain the sensitivity and reliability of the protection while reducing at least 44% of the system traffic whenever internal or external faults occur. It facilitates the realisation of wide-area differential protection in practice. Through digital simulation and dynamic simulation, the study demonstrates that the algorithm can distinguish fault places correctly and features a relatively high degree of sensitivity.

Adaptive Agent-Based Wide-Area Current Differential Protection System

This paper proposes a multiagent-based adaptive wide-area current differential protection system. A power grid is divided into primary and backup protection zones dynamically online with the help of a developed expert system, and the relay agents of these zones cooperate to perform a differential relaying function. Predictive self-healing strategies have been proposed to prevent misoperation of the relay agent, and the communication system has been simulated. The performance of the proposed adaptive wide-area current differential protection system based on computer simulation is presented in this paper.