An Approach Of Fault Analysis And Fault Locating Of Power Transmission Lines Based On Transient Signals

The power industry has a large scale and rapid development.Transmission line is of great significance and wide distribution in the power system and its operational safety is increasingly threatened by many factors.When the power system fails,timely and accurate fault analysis and locating can provide a reliable basis for fault handling,which is of great importance to the safe operation of the power system.At present,the methods of fault analysis and locating are facing many challenges: the rapid action of relay protection makes less data to be collected,which results in difficult extracting of steadystate signals;the randomness and time variability of the short-circuit transition resistance and the distribution characteristics of the transmission line all affect the accuracy of fault analysis and locating.In order to cope with the above problems and improve the accuracy and adaptability of fault analysis and locating,this paper proposes a method for processing faults in power transmission lines based on constraint of circuit and doubleend transient fault data from fault recorders.The main research methods and results are as follows:Firstly,a method of transient signal fitting and sinusoidal representation based on Hilibert Transform is proposed.Adopting new fitting modle,this method can be used to accurately fit the transient signal of transmission lines and obtain its nth order derivative,instantaneous amplitude,instantaneous phase and other characteristics,which can be seen from the theoretical derivation and simulation verification.Sinusoidal representation can be used to decouple and inverse the transient signals with the instantaneous symmetrical component transform.Also,they can be used to calculate the distribution of the transient signal along the line with the distributed parameter model of transmission line.These three technical means together lay the foundation for fault analysis and locating.Secondly,considering various transition resistances and their time variability,a method for fault analysis of transmission lines based on transient signals is proposed.With the help of three technical methods,combining the principle of voltage continuity and its instantaneous amplitude consistency,the principle of consistent instantaneous phases of voltage and current on the transition resistance,the characteristics and calculation methods of the transition resistance are studied,the analysis of four simple short-circuit faults is realized,and the fault voltage,current and transition resistance are calculated.Compared with current fault analysis method,this method can obtaine every transition resistance with time variability.ATP/EMTP simulation cases and field cases from Chongqing Power Company are respectively simulated in MATLAB.The correctness of this fault analysis method is proved by the simulation results of four different simple short circuit cases.Field cases show the practicability of this method.Thirdly,this paper proposes a method of fault locating of transmission lines mainly based on the consistency of instantaneous phase.Based on the principle of voltage continuity and its instantaneous amplitude consistency,the fuzzy fault interval is determined by using the dichotomy method.Furthermore,based on the principle of consistent instantaneous phases of voltage and current on the transition resistance,specific locating criteria for four types of simple short-circuit faults are derived,and the exact fault points are determined in the above interval using enumeration method.These simulation cases and field cases is sufficient to indicate the accuracy and effectiveness of the hierarchical fault locating method that is not affected by fault types,line parameters,fault locations and time-varying transition resistances.The approach of fault processing of power transmission lines has not to assume that the transition resistance is constant or the phase transition resistances are the same,which is more general.Simulation and field cases show that this method is suitable for fault analysis and fault locating in power system,and provides a reference basis for current grid fault handling and recovery.