Research On Cable Fault Diagnosis Based On TDR/SSTDR

Cables are widely used in various applications of energy and signal transmission.In aerospace systems,cables are characterized by large number,large weight and complex structure.As the system requires higher and higher reliability of cable,the demand for cable fault diagnosis is gradually increasing.Time Domain Reflectometry(TDR)and Spread Spectrum Time Domain Reflectometry(SSTDR)still have some problems in the application of cable fault diagnosis: 1)For single cable fault diagnosis,the existing diagnosis methods have some problems,such as low location accuracy,blind area,difficulty in arc fault diagnosis,and so on.Cable fault diagnosis method is of great significance for accurate location of cable fault,enlarging diagnostic range and finding arc fault in time.2)At present,for cable network fault diagnosis,it is mainly based on the combination of TDR and intelligent algorithm to realize cable network fault diagnosis.This method can only be applied in off-line situation,but can not realize cable network fault online diagnosis.The research of on-line fault diagnosis method based on STDR cable network can improve the real-time and security of system diagnosis.Firstly,the causes of low location accuracy and the existence of diagnostic blind zone are analyzed.A high-accuracy cable fault diagnosis method suitable for TDR and SSTDR without blind area is proposed in this paper.The location accuracy is improved by reducing the time measurement error and the error of signal propagation speed.The cable fault diagnosis without blind zone is realized by fitting the fault waveform of the cable in the diagnostic blind zone,the theoretical analysis and simulation verification are carried out.For the difficulty of SSTDR cable serial arc fault diagnosis,this paper proposes a method of summing the differences to weaken the interference of arc noise,increase the amplitude of reflection wave at arc fault point,and verify its feasibility by simulation.Secondly,the on-line fault diagnosis method of cable network is studied.The online fault diagnosis of Y shaped network which is the Minimum Network Unit is carried out.The fault characteristics are studied through the physical model of the network fault.Based on this,the fitting parameters are used to fit the fault waveform of the cable network.Combined with SSTDR,an on-line fault diagnosis method for Y shaped network based on fault waveform fitting is proposed.The theoretical analysis and simulation verify the above methods.An on-line fault diagnosis platform for Y shaped network is built,and the effectiveness of the method is verified by experiments.Finally,based on the solution of the above key problems,a cable fault diagnosis device based on TDR and SSTDR is designed,and an experimental verification platform is built.The experiment verifies the feasibility of the high-accuracy cable fault diagnosis method suitable for TDR and SSTDR without blind area and the effectiveness of the SSTDR cable serial arc fault diagnosis method.