Single-phase Adaptive Reclosing Criterion Of Ultra High Voltage Transmission Line

There are two key problems for single-phase adaptive reclosing of Ultra High Voltage(UHV)transmission lines: discrimination of the nature of the fault and the best time to coincide capture.The role of fault nature of the judgment is that the permanent failure to block the circuit breaker so that no longer coincide,so as to avoid the system by the second shock;The best coincidence capture is to stabilize the system when it coincides with an instantaneous fault.In this paper,from investigating the difference of fault phase voltage under two kinds of fault,single-phase adaptive reclosing criterion is proposed;By studying the transient stability of the system and the improved neural network,an intelligent approach to capture the optimal coincidence time is presented.Firstly,this article systematically introduces the single-phase adaptive reclosing research background,significance and development status at home and abroad;The characteristics of arc,sub-current and fault phase voltage under different fault characteristics in single-phase-to-earth fault of power transmission line are explored.The power system model of 1000 kV UHV transmission line with parallel reactors at both ends is built on the PSCAD/EMTDC simulation platform,then the terminal voltage waveform of fault phase is simulated.Secondly,the difference of the fault phase voltage with two kinds of fault properties are researched and the Voltage Change Rate Energy Ratio(VCRER)is put forward.The rationality of VCRER is obtained through strict mathematical derivation.By continuously calculating the VCRER ratio of two adjacent time windows,and then comparing with the set threshold to distinguish fault property,the effective criterion is obtained.The simulation results show that the new criterion is still valid under different noise environments.Finally,The system transient stability,Empirical Mode Decomposition(EMD)and BP Neural Network Based on Plant Growth Simulation(PGS-BP)are analysed,an intelligent method is bring forward to capture the optimal reclosing time based on PGS-BP algorithm.