Investigation on the Voltage Dependence of Compressed-Gas-Insulated Capacitors up to 400 kV by Improved Voltage-Doubling Method

Abstract

This paper presents a recent improvement in the measurement of voltage dependence of compressed gas capacitors up to 400 kV using the voltage doubling method. Two identical 10nF high-voltage capacitors in series are employed to generate voltage-doubling operating points and this proved to be effective in providing consistent harmonic content for voltages. A commercial ground current comparator bridge is used to compare the capacitor under test with a reference capacitor at equal voltage and double voltage, respectively. In order to accurately determine the ratio of the voltage applied across the reference capacitor and the capacitor under test in the voltage doubling state, the other current comparator bridge with floating remote transmission function is developed in this paper to monitor the voltage ratio of the doubling voltage. The two current comparator bridges perform measurement process simultaneously without prior knowledge of the voltage coefficient of the reference capacitor. In this paper, the influence of the working state of the floating current comparator bridge on the measurement is determined by an inductive voltage divider. The experiment results show that the expanded uncertainty of the proposed method for measuring the voltage coefficient of capacitance and loss of 400 kV high-voltage capacitors is estimated to be about 5 ppm.