Design And Application Of The Instrument Of Power Cable Fault Location

Power cable fault occurs regularly in power system. Fault location is the precondition to eliminate the fault. Accurate fault location can reduce the time to find out the fault point and the cost power cable cut.This paper first introduce spread process of the electric voltage, electric current wave in the electric cable circuit, the electric power electric cable belong to a kind of delivering line, which can look as the coupling constitution of much more electric resistances, electric conductivity, electric capacity and inductance, these all the electric parameters are called the electric cable distributing parameter. According to the power cable distributing parameter and wave equation of square wave transmitting in the power cable, it can deduce electric voltage echo coefficient of square wave on the power cable fault point, the echo coefficient of short circuit is -1, open circuit's is +l,and the voltage echo coefficient of low electric resistances fault is to lies in the both of the two faults. The electric voltage echo coefficient provides dependable theories to the power cable fault location.Then, the paper introduces the many kinds of methods of power cable fault location. The traditional measure is adopting the electricity bridge to locate fault. But along with the technical development in electronics technology and establishment in the power cable distributing parameter theory foundation, it appears the low voltage pulse method and pulse electric current method, and the pulse electric current method is divide into the two kinds of direct current high voltage flashover method and striking high voltage flashover method. And introduce simply the every kind of method advantage, weakness and their connecting line methods.The next, the paper introduce the hardware design project of the instrument of power cable fault location. As a kind of intelligent precise locating instrument, it must attain the very high request in measuring accuracy, so, adopting the two parallelingslices of exceeding-speed A/D converter to increase the transiting speed by two times. For the exceeding-speed data gathering frequency, the common data transmission system is to can't up to the request, here introduces a kind of on -board RAM transmission method. Setting a "quick enter slow out" RAM, it first write the ADC result to the high speed buffer and then send to the host computer main memory.Finally, using of foundation theories of the electric pulse transmitting and echoing in the power cable, it can establish integrity model of power cable fault location, and adopt the MATLAB software to imitate the system model and the results composed of a series of data with the experimental waveforms are gained. It is shown from the results of the simulation, and the efficiency of the fault model in the paper is validated.