Fault Location Of HVDC Transmission Lines Based On Abrupt Capacitance

With the continuous development of the national economy,more and more residents and industrial use of electricity,so the transmission system for the safe and stable operation of the requirements are also getting higher and higher.in order to meet the requirements of the development of modern power grid,flexible HVDC system has been adopted gradually.flexible HVDC system using full controlled device IGBT,it can realize the self turn off the current of the system,compared with the conventional HVDC system,flexible HVDC system can supply power to a passive network,isolated load distance,therefore flexible DC transmission system is bound to continue to develop in the HVDC system,the line is relatively long,and the operating environment is bad,so compared with other transmission equipment failure rate is relatively high in order to ensure the safe and stable operation of DC transmission system,it is necessary to determine the location of the fault and remove the fault in the fault of the DC line.This research is on the fault location of flexible DC transmission line,is mainly to the DC line on monopolar grounding fault location,so at first this paper introduces two common fault location method of single ended and double ended;in order to better understand the DC system,then the main components in the VSC-HVDC system are introduced,such as the structure and principle of IGBT;zero mode network grounding fault to VSC-HVDC application of DC transmission lines and 1 mode network,through simulation of zero mode network and the 1 network model in this paper,the equivalent network structure in HVDC system zero mode network graph,so as to arrive at the zero mode network,rectifier part in VSC-HVDC system can be equivalent to a parallel capacitor is proposed based on the conclusion,the capacitance of the mutation Fault location principle,laid the foundation for the subsequent analysis of fault location principle;and to compare the relationship between zero mode voltage and zero mode current and the identification of capacitor,will also need to decouple the voltage and current component of zero mode network,through the numerical voltage current component to calculate decoupling zero mode capacitance for fault recognition;Study on DC line fault,traveling wave arrival time,this paper built in PSCAD DC transmission line for rectifier part of HVDC flexible system and converter is used with the PSCAD model of software;for the DC line model selection is the distance termination mode to build the transmission line,the distributed parameter model uses the Bergeron model;finally the simulation of grounding fault in DC line monopole to build a good model,in full Long 100 KM,rated DC voltage for DC line + 110 KV on the fault set,mutation pattern comparison zero mode voltage,zero mode current and the identification of capacitor in the DC line of different positions and the changes in the case of different transition resistance,and draws the conclusion that in the zero mode network fault.Localization of the mutant capacitance can occur after fault for reliable identification of wave arrival time based on,and is not affected by the fault distance,influence of electrical waveform gradient and can adapt to the high resistance grounding fault of different transition resistance.