Research On The Method Of Cable Fault Automation Location Based On Low Voltage Pulse

Power cable has the advantages of safety, high reliability and beautification of urban layout With development of our country's economy, the application of power cable is more and more widely in urban distribution system. Along with the increasing application and running time of power cable, the fault occurs are also more and more frequently, which brings forth user huge damage. Therefore, examining the fault of power cable fastly and accurately and finding out the fault position have the extremely significance to guarantee the power quality.At present traveling wave method is widely used in the cable fault location, whose merit is that its veracity of location is not influenced by the fault type theoretically. But the traveling wave signal attenuates as a result of the line core insulation dielectric loss, the reflection of the joint and other disturbances, so the directly automatic location to the fault of cable is very difficult. Generally operators firstly regulate the wave of the fault signal to the appropriate size in the display screen of the location instrument, then separately move the cursor to the discharge pulse and the reflection pulse initial station, finally compute the distance of the fault. This method is not convenient for the users and the precision is functioned by the user's experience. Its intellectualized degree is lower. Kinds of disturbances and the attachment reflection bring difficulties to the recognition and the localization of the fault.In this paper, an intelligent method of cable fault automatic location which based on the principle of low voltage pulse reflection is introduced. It shapes the fault reflecting wave into rectangular pulse, overcomes the reflection of the cable joint by setting threshold voltage and eliminates some other noise interferences by correlative processing in the signal utilizing correlation function. This method can calculate the distance of fault and judge the low resistant short-circuit and open-circuit fault automatically. The software is realized on the device of cable fault location based on the virtual instrument, and a practical test is made on a section of cable. The experimental results demonstrate that the method is valid and correct.Intelligent instrument of cable fault location based on virtual instrument is designed. The hardware contains Puyuan science and technology product: the RVO3100B instrument, the cable test pulse signal generator and the notebook computer. The man-machine contact interface of digital measuring system which based on virtual instrument is designed by using Visual Basic 6.0 as the visible programming language. The software includes initialization module, parameter setting module, data collection module, data display module and data processing module. The characteristics of the system including reasonable configuration, reliable capability, high integration and convenient installation fully show the merits of virtual instrument.With the aid of the MATLAB simulation platform, the simulation model based on low voltage pulse method is established, and fault waves of short-circuit and open-circuit are gained. The simulated wave is processed with the method which was proposed in the article, and the method is confirmed feasible by the results.