The On-line Fault Location Study On Coal Mine Underground Power Cable

At present, the majority of coal mine electrical network are consisted by the short multi-segment power cables,due to the poor condition in the coal mine, the transmission line often occur single-phase to ground short-circuit fault, when the transmission line occurs insulation failure, it is quite difficult to quickly find the exact fault point, so far, the fault location in the coal mine underground transmission line still lack a effective mean. When the coal mine transmission line occurs fault, exactly search the fault point not only can reduce the burden on patroling and can shorten the fault point shooting time, as well as speed up the restoration of power supply, but also can early detect the weak point of the transmission lines, reduce the losses of power failure, therefore, accurate fault location has a great value.When the coal mine unground transmission line occurs single-phase to ground short-circuit fault, high frequency transient traveling wave caused by the fault point will spread to the both ends of bus bar, the previous fault location methods often take the transient traveling wave as the harmonic interference, actually, high frequency transient traveling wave also contains rich fault distance information, using the high frequency transient traveling wave can definitely realize the precise fault location, the method of traveling wave fault location is based on the above principle.On the foundation of carefuly analysize the transient traveling wave spreading process and its influencing factors, this paper use the wavelet transform's time-frequency localization characteristics to extract the fault distance information , then by compare the polarity of wave wavelet transformation mode maximum value, can accurately get the reaching time of initial traveling wave,the fault point reflected waves and the end bus reflected waves, then can realize the fault location.Although the principle of traditional single-end traveling wave fault location is simple, it is difficult to distinguish the reflected wave polarity, and there is a blind spot of fault location when the fault occur in the near zone of the transmission line. Although double-end traveling wave fault location is not affected by transmission line type and fault transient resistance, requires the time of both bus bars is precisely same. No matter is the single-end traveling wave method or double-end traveling wave method, because of the traveling wave velocity is indefinite, which will result in an inaccurate fault location result, and coal mine is a single-end power supply system, only can use the single-end traveling wave fault location method. In view of the shortcoming of traditional single-end traveling wave method, on the foundation of single-end traveling wave fault location method, this paper propose a new single-end traveling wave fault location method which uses the wave velocity automatic compensation, in view of the key factors which will affect the accuracy of fault location, this paper propose the corresponding solution. Simulation result proves that this algorithm can effectively solves the problem of mine unground transmission line fault location.