Author(s)

Y. Mitoma, H. Yoshizumi, S. Uematsu, T. Ishii, K. Amano & T. Tanaka

Abstract

When a ground-fault problem occurs on a 6.6 kV power distribution line, it is essential to locate the fault point immediately and restore power to that line as soon as possible. However, in a combined system of both insulated wires and cables, surge signals could be affected by attenuation and reflection at both connected points and branch points, making an accurate determination of the fault point more difficult. Moreover, the surge signals of a 6.6 kV ungrounded power line are smaller than those of an ultra-high voltage grounded power line, further making it difficult to detect surge signals. Therefore, we have developed the fault location system and conducted verification tests on a fault locator on a 6.6 kV power distribution line. The ground-fault point is detected by measuring surge voltage propagation at both ends of line utilizing both noncontact voltage sensors and GPS (Global Positioning System) synchronizing technology. We found it important to acquire the first arrival surge and determine the surge traveling speed. These two points are key factors in improving the accuracy of the fault locator. First of all, as the power line produces much base noise, we have difficulty acquiring the first arrival surge. To solve this problem, we succeeded in developing a differential amplifier which improved the S/N (Signal /Noise) ratio. Secondly, we have established a method of calculating the fault point and the surge traveling speed from the switching surge in the combined insulated wire and cable system. In conclusion, we have conducted verification tests, enabling us to detect the fault location with an error rate ranging from 278 m to 363 m (3%) at a distance of 12.258 km. We are continuing work to improve the system. Keywords: fault locator, 6.6 kV power distribution line, surge signal.

Keywords

fault locator, 6.6 kV power distribution line, surge signal