Research On Fault Location Of Hybrid Line In Distribution Network Based On Traveling Wave Natural Frequency

Distribution network structure is complex,and there are a large number of branch lines and overhead line-cable hybrid lines.When a fault occurs in the distribution network,the traditional fault location methods have poor adaptability in the distribution network,and they are difficult to promote to the distribution network hybrid line.Therefore,it is of great significance to study the fault location method of hybrid line in distribution network.Compared with the time domain traveling wave method,the frequency domain traveling wave method focuses on the frequency information of the fault traveling wave,without obtaining the arrival time of the traveling wave and identifying the fault traveling wave head.The principle is simple and the cost is low.It has great potential in the field of fault location of hybrid lines in distribution network.Based on the frequency domain traveling wave method,this paper explores the feasibility and adaptability of the method in the hybrid line of distribution network,and studies the fault location methods of single hybrid line and hybrid line in distribution network respectively.Firstly,the principle of frequency domain traveling wave method is deeply analyzed,and the relationship between natural frequency of traveling wave and fault distance is established.Multiple signal classification(MUSIC)algorithm is used to extract traveling wave natural frequency,and the process of fault location using traveling wave natural frequency is summarized.In a single hybrid line,the fault traveling wave signal will have the phenomenon of spectrum aliasing.The use of variational mode decomposition(VMD)algorithm can well overcome the phenomenon of spectrum aliasing.The combination of VMD algorithm and MUSIC algorithm can effectively extract the traveling wave natural frequency from the fault traveling wave signal of a single hybrid line.This paper studies the fault location method based on the main frequency sequence of segmented natural frequency and the fault location method based on the harmonic natural frequency.The VMD algorithm is used and the fault location method based on the harmonic natural frequency is taken as the main body to form a single hybrid line fault location method.This method can achieve good fault location results under different fault distance,different fault types and different transition resistance,and has good adaptability and accuracy.In order to solve the problem of location difficulty of hybrid line in distribution network due to complex structure,the fault section location method of hybrid line in distribution network based on multi-terminal natural frequency is studied.By analyzing the propagation path of fault traveling wave in hybrid lines,the fault section location rules of hybrid line in distribution network are summarized.In addition,in order to avoid the failure of multi-terminal natural frequency fault section location method due to multi measurement points failure,the fault location method based on single-terminal equivalent frequency is used as an auxiliary method when multi-terminal method fails.When the equivalent frequency of the fault is measured by the single terminal measuring point,the fault distance can be determined according to the equivalent frequency and the hybrid line parameters of the distribution network,and the fault location can be realized.This method can accurately calculate the fault distance,has high positioning accuracy,and is not affected by the fault type,transition resistance,initial phase angle and noise interference.It has strong adaptability in the hybrid line in distribution network,and can be used as an auxiliary fault location method when the multi-terminal method fails.The above research shows that the frequency domain traveling wave method can realize fault location of single hybrid line and hybrid line distribution network,and has strong adaptability.This paper has 30 pictures,16 tables and 113 references.