Research On Noise Time Domain Reflectometry Measurement For Cable Fault Detection

With the rapid development of economy and society,cable as an important transmission medium is used frequently in aerospace,high-speed rails,ships and other large vehicles.As the cable is often inevitably vulnerable to external forces,chemical corrosion in adverse circumstances,and its own insulation aging.How to improve the reliability of cable operation is an important research topic in the field of cable.In order to achieve on-line detection of cable fault and simultaneous detection of fault on bundled cables and different branches of multi-core cables,we have made the attempt to apply noise signals to cable fault detection.In this paper,noise signal as a detection signal was used to detect the cable fault.The main researches are as follows.1.The application range of cable and the causes and types of cable fault were stated.The common detection methods of cable fault were summarized.By analyzing and comparing the advantages and disadvantages of these methods,the noise signal used as the detection signal to detect the cable fault was put forward.2.The theoretical basis of measuring cable fault based on noise time domain reflectometry is analyzed.Using the noise signal as a test signal,it can realize on-line detection of cable faults as long as it has a similarity to the ?-type function.3.The noise signals outputted by the silicon zener diode in the reverse circuit were used as the detection signal,and the open circuit,short circuit and impedance mismatch of the coaxial cable were tested.The experimental results showed that the maximum detection distance is 2000 m.The relative error is around 2.5% in the detection range of 600 m,and the relative error is limited to 5.6% in the detection range of 2000 m.At the same time,a simple digital communication system was built in order to realize the on-line detection of the transmitting signal cable in the system.The experimental results showed that the error rate of the noise detection signal to the communication system is less than 5.82E-10.4.The multi-channel filtered amplified spontaneous emission noise was used as the bundled cables or different branches of multi-core cables detection signal to detect different branches of cable failure with no mutual interference.The open circuits,short circuits and impedance mismatch of the bundled cables were tested.The experimental results showed that the maximum detection distance is 720 m,and the relative error is near 0.8% in the measurement range of 50 m.Within the measurement range of 700 m,the relative error is controlled within 2.6%.In addition,the experiments verified that the method can realize the on-line detection of cable fault.