Research On Fault Location Of 10kV Cable Based On Time-frequency Composite Analysis Of Sheath Current Traveling Wave

Power cables are an important part of the urban power grid,and the efficiency of fault detection and repair directly affects the reliability of the urban power grid.At present,about 80% of the types of faults that occur in distribution network cables are single-phase ground faults,and the incidence of faults is much higher than that of two-phase short-circuit,twophase ground,and three-phase short-circuit faults.When a single-phase ground fault occurs in the cable,in order to avoid multi-point faults such as two-phase(ground)short circuit and three-phase short circuit caused by the ground fault,the fault location is quickly and accurately identified,and the hazards of the fault are quickly eliminated.The safe and stable operation of the power grid is of great significance.Aiming at the particularity of the cable's own structure,this paper fully considers the electrical characteristics of the metal sheath structure when the cable is faulty,and proposes a new cable fault location method—fault measurement based on the composite analysis of the traveling current time-frequency of the sheath current Distance method.Firstly,the actual operation of the power cable is introduced,mainly including the cable laying mode and the metal sheath grounding mode.Then,a cable model considering the cable metal sheath structure is established,and the electrical parameters of the cable and the transmission characteristics of each modulus of the cable system are analyzed and calculated according to different cable laying methods.Secondly,in order to accurately extract the feature information in the fault transient traveling wave signal,this article discusses the signal processing method,which focuses on two algorithms: time domain feature extraction algorithm—MEEMD algorithm and frequency domain feature extraction algorithm—FFT-MUSIC.For the frequency domain feature extraction algorithm,this paper combines the FFT algorithm with the MUSIC algorithm to estimate the frequency domain feature quantity.For the time domain feature extraction algorithm,this paper uses the MEEMD algorithm to identify wave head information.The accuracy and effectiveness of the time domain method and frequency domain method are verified by simulation analysis.Finally,for the fault location method of time-frequency composite analysis,this paper expounds the mathematical relationship between the natural frequency and the fault distance,the principle of the frequency difference method,and the ranging steps and advantages of the time-frequency composite analysis ranging method.Through a large number of examples,it is verified that the time-frequency composite analysis method can accurately identify the secondary reflected wave head,which improves the accuracy of the traveling wave frequency domain analysis and the feasibility of time domain analysis.Comprehensive analysis in the frequency domain has achieved better cable single-phase grounding fault location.Then,through a large number of experiments,the adaptability analysis was carried out to verify that the new fault location algorithm for time-frequency composite analysis under different operating conditions of the system,The ranging results have high accuracy and reliability.