Self-Correction Sensor for Measuring Medium DC Voltage Based on Resistance Voltage Divider

Abstract

With the rapid development of the direct current (DC) distribution network, DC voltage measurement technology is increasingly important to ensure safe operation of the distribution network. The measurement accuracy of the traditional sensor based on resistance dividers decreases over time because the resistors age due to temperature and electromagnetic radiation. Addressing this problem, a novel type of medium-voltage DC voltage sensor with self-correction ability is presented in this paper. A resistor with large RH is connected in series with RK and RG, two precise resistors with low resistance, to transform the measured medium voltage into low voltage. Among these three resistors in the divider, RH connects with the measured medium DC line, while RG connects with the ground. An electronic switch, K, is paralleled with RK, the precise resistor at the middle position. Generally, the state of the electronic switch is off, and the current flows through RK. Medium DC voltage can be measured according to the voltage on RG and the divider ratio. When the sensor needs self-correction, the electronic switch will be controlled by FPGA (Field Programmable Gate Array) to turn it off and on; therefore, two values of low voltage can be obtained using time-sharing sampling. Two equations can be built according to the divider principle, and RH in the divider can be evaluated by solving the equations. As a result, the measurement error caused by the change in RH can be avoided. Finally, the medium-voltage DC sensor developed in this paper was tested at the Institute of High Voltage, Wuhan, China. The experimental results show that the sensor can perform self-correction without manual operation, and the sensor's accuracy can reach 0.12%. Sensors with self-calibration function can realize long-term high-precision measurement without manual maintenance, showing a good application prospect.