Research On Setting Method Of Time Domain Distance Protection For Transmission Line

Distance protection does not depend on communication channels,which is of great significance for the safe operation of transmission lines.However,with the integration of new energy sources such as wind power and photovoltaic power generation into the power grid,due to the frequency deviation and higher harmonic of the wind power side,and the weak-infeed property of photovoltaic power generation,the line fault voltage and current frequency are inconsistent,which affects the reliability of frequency domain distance protection.The time domain distance protection is not affected by changes in the frequency of the power grid,and can be used for tie line protection after grid connection such as wind power and photovoltaic power generation.At present,there is no theoretical basis for the setting calculation of time domain distance protection,and the frequency domain distance protection setting method is still used in the time domain distance protection.A method of time domain distance protection setting method using simulation calculations is proposed in this paper.Firstly,the influencing factors of the impedance calculation results of the time domain distance protection are analyzed.The model error,transformer error,fault position,fault type,transition resistance,time window,electromagnetic interference and other factors are considered.The setting process of time domain distance protection is given.The fault simulation schemes are formulated,and various combinations of conditions are given.The transmission system and line simulation model are established using PSCAD/EMTDC.Taking the directional impedance relay as an example,the action boundary of the protection is determined by the external faults,the sensitivity of the protection is determined by the internal faults,and the protective setting values are given.The PSCAD/EMTDC simulation results show that,using this method to achieve the time domain distance protection setting can improve the protection sensitivity.Secondly,a value setting program for time domain distance protection based on digital simulation is developed.Using digital simulation to achieve setting,the workload is relatively large.In order to improve the work efficiency,the GUIDE module of MATLAB is used to develop the setting program of the time domain distance protection setting,including program start interface,data import module,the simulation parameter setting module,waveform display module,measurement impedance calculation module and setting calculation module.It can realize the functions of waveform viewing,measuring impedance calculation,setting calculation and so on,and has good man-machine interaction functions.