Abstract
In a fault location system by the current surge detection, the difference time of arrival on the fault current surge is measured at two positions on either side of the fault point. However, a rounding of the wave caused by a frequency characteristic of the power cable degrades the accuracy of the fault location. To improve the accuracy, we use some signal processing method, a frequency compensation, a decision algorithm of a pulse arrival timing form the rounded pulse, and estimation of the surge velocity in the power cable with high accuracy. In the frequency compensation, a digital filter with the inverse of frequency characteristics of this power cable is designed. The rounded surge at the measured point is sharpened by this inverse filter. The velocity of the surge in the power cable is estimated from the measurement of the phase characteristics of the cable. The velocity estimated as mean value of the phase characteristics slope weighted by the frequency spectrum of the surge.
A 1/10 scaled model of 275 kV cross bonded cable system was built for the test of real time fault location system. The relative location errors defined by the ratio of error distance and the location base length are measured at seven artificial fault points, and results of the accuracy estimated from each algorithms. As a result of signal processing the accuracy of the fault location had been improved with the location error within 0.5%.
