Non-fault Identification Criterion For Single-phase Reclosure On UHV Transmission Lines

Most faults on ultra high voltage (UHV) transmission lines are single-phasetransient faults because of the long phase-to-phase insulation distance. Single-phasereclosure is widely used at home and abroad to improve the sustainability and reliabilityof power supply. But present single-phase reclosure techniques on UHV transmissionlines have poor ability of detecting non-fault before reclosing because of using afixed-time scheme. Reclosing will fail when the fault still existed. Detecting non-faultbefore reclosing is useful to improve the success rate of reclosure. Therefore, study onnon-fault identification criterion for single-phase intelligent reclosure has importantsignificance.This thesis studied the amplitude and frequency characteristics of open-phasevoltage and shunt reactor current with different shunt reactor compensation degree underdifferent single-phase faults, analysed the beat mechanism and conditions of transientfaults. Study showed that: when faults were arcing, the open-phase voltage and reactorcurrent only had power-frequency periodic component, no low-frequency periodiccomponents. When faults disappeared, the open-phase voltage and shunt reactor currenthave low-frequency and power-frequency periodic components. Moreover, reactorcompensation ratio has great impact on the amplitudes of open-phase voltage and shuntreactor current. However, the frequency of low-frequency is determined by the inherentparameters of the line. A non-fault identification theory based on low-frequencycharacteristics of open-phase voltage and shunt reactor current is developed. But,Common FFT algorithms can not extract the frequency and amplitude information of thelow-frequency component accurately and fastly. Prony algorithm can extract thefrequency and amplitude information of the low-frequency component whin short time.Therefore, a non-fault identification criterion based on prony algorithm is developed.In this thesis, use ATP software simulation and physical test to verify the non-faultidentification theory and criterion. Firstly, build the UHV transmission line model by ATPThese works are supported by National Natural Science Foundation of China (No．51207119)，Natural Science BasicResearch Plan in Shanxi of China (No．2010JM7013)． software, large number of ATP simulations under different fault conditions and faultnature verified the effectiveness and reliability of the criterion, and the criterion isindependent on system running state, fault location, fault resistance and the load current.Secondly, build a miniature physical model of UHV transmission line, use virtualinstrument technology to achieve data acquisition. Data analysed by LabVIEW andMATLAB. Data analysis under different fault location and fault nature verified that, thenon-fault identification theory and criterion for single-phase reclosure whit good validityand applicability, laied a good foundation for engineering applications of smart singlephase reclosing in the future.