Measurement Uncertainty in Voltage Coefficients for Compressed-Gas Capacitor Based on a Simplified Tilting Method

High-voltage compressed-gas capacitor is a type of precision equipment commonly used in high-voltage laboratories. The voltage dependence of capacitance, in other words, the voltage coefficient (VC) of capacitance, is an important factor to ensure the measurement accuracy of capacitors. The simplified tilting method (STM) derived from PTB, which provides a solution for measuring the VC of the high-voltage capacitor with compressed-gas coaxial cylindrical electrodes structure. However, it is not an easy work for most laboratories. In order to evaluate the VC based on the STM, a special experimental platform was developed. The high-voltage capacitor installed on the platform can be tilted and rotated at high voltage and can be remote-controlled. Based on the developed platform, the VC of a 350-kV high-voltage capacitor was measured. In order to verify, it was remeasured by the direct measurement method with a dummy high-voltage capacitor, and before that, the VC of the dummy capacitor was calibrated with a near zero-VC capacitor. The results show a good agreement, and the consistency of the measurement results is better than 1.2 $\times \,\,10^{-6}$ between the two methods. Furthermore, the evaluation of measurement uncertainty in the VC determination of capacitor based on STM is introduced in detail. The evaluation results show that the expanded uncertainty is significantly better than 2.0 $\times \,\,10^{-6}$ , $k =2$ .