Design of High Voltage Dielectric Spectroscopy Measurement System for Bushing Moisture Detection

Abstract

Frequency domain spectroscopy (FDS) has proved to be an effective method for moisture assessment of power equipments. However, traditional FDS testers are mainly designed for material measurement. Therefore, the test voltage used is usually not more than 2 kV, which led to unsatisfactory performance when measuring large power equipments. In order to obtain higher accuracy when measuring power equipments, taking into account that the increase in voltage makes it possible to find the connection between test voltage and dielectric spectroscopy, a high voltage dielectric spectroscopy measurement system for bushing moisture detection was designed. Firstly, the hardware architecture of the system was designed based on the FDS measurement principle. Then a prototype was built according to the design. The algorithm for data processing is also introduced in this paper. The measurement accuracy of the system was verified by comparison with a commercial FDS tester. Finally, two bushings with different moisture content was measured using the designed system. The results indicate that when the test voltage rises, the dielectric spectroscopy of the bushing with higher moisture content changes more significantly and regularly than the other. The feasibility of this system for bushing moisture detection is thus proved.