Influence of temperature variation on the accuracy of DC voltage measuring device

DC voltage measurement device is the key equipment in the DC transmission system, which is mainly used for system voltage measurement and providing voltage signals to the measuring instruments and secondary protection devices. With the rapid development of DC transmission and flexible transmission in China, DC voltage measurement device has been widely used and developed. High accuracy and high stability is required for the DC voltage measuring device used in the system. The accuracy of the voltage measurement in HVDC project is generally required to reach 0.2%. In recent years, the accuracy characteristics of the DC voltage measuring device were studied by related technical stuff. The mainly reasons for the impact of the accuracy were found: voltage change between resistive elements, changes and instability in resistance due to the heat of the resistor itself, corona discharge, leakage current of the insulation bracket, etc. Combined with the structure characteristics of the DC voltage measuring device, the influence of the temperature variation on its accuracy is further analyzed in this paper. Due to the different rated operating voltage, the internally generated heat of the voltage divider will be different for different voltage level of DC voltage measurement device. Except the changes and instability in resistance due to the heat of the resistor itself, the temperature difference in the height direction of the voltage divider will also increase. This phenomenon will cause the ratio of voltage divider to change and affect the accuracy of the DC voltage measurement device. The results of the analysis were further verified by actual test, and some suggestions on the ratio test of the DC voltage measurement device in the national standard were presented in this paper.