Calibration method and basis of high voltage active voltage divider

作者： GOZ Electric 时间：2024-12-13 09:06:14 阅读：23

Abstract: The high-voltage active voltage divider is a high-precision measuring instrument based on the principle of current comparator. It is used in conjunction with a compressed gas capacitor to provide a method that can automatically correct amplitude and phase errors without an external adjustment controller. At present, there is no technical specification for active voltage divider measurement in China.

In order to solve the problem of traceability of the value of the active voltage divider, a calibration method based on the equal power bridge method is adopted. Through experiments and data analysis, the problem that the active voltage divider has no relevant calibration basis is solved.

Keywords: active voltage divider; current comparator; equal power bridge method; calibration

When measuring high voltage, it is required to use an accurate method to reduce the high voltage to a low voltage in proportion for measurement. The commonly used measurement devices are electromagnetic voltage transformers and high voltage dividers. Electromagnetic voltage transformers use the electromagnetic coupling principle, have high measurement accuracy and good stability, and are generally used as the highest standard. The voltage divider uses the impedance voltage division principle to obtain secondary low-voltage output, which is mainly divided into three principle forms: resistance, capacitance, and resistance-capacitance hybrid. The compressed gas capacitor is connected in series with a large-capacity solid capacitor, and the back end is equipped with an electronic unit to form the most basic high-voltage active voltage divider. The structure of the high-voltage active voltage divider is characterized by the use of compressed gas capacitors as high-voltage arm components, and the insulation of the primary high voltage is borne by the high-voltage arm gas capacitor: different voltage levels can be easily achieved by matching high-voltage capacitors of different voltage levels. The characteristics of the capacitor determine that it has good phase characteristics, but because the capacitor is used as a voltage dividing element, it is affected by temperature and voltage effects. Compared with the standard device of electromagnetic voltage transformers, the long-term stability of the high-voltage active voltage divider is slightly worse.

1 Basic principles

The high-voltage active voltage divider is essentially a capacitive voltage divider. Its basic principle is shown in the figure:

2 Basic principles of calibration

The calibration of the active voltage divider refers to the equal power bridge method in the verification procedure of JG496-2016 "Industrial Frequency High Voltage Divider". The active voltage divider needs to be equipped with a high-voltage reference capacitor and a low-voltage reference capacitor to form a capacitive high-voltage voltage divider. The high-voltage terminal is connected in parallel to the primary high-voltage side and connected to the output end of the active voltage divider. The signal measurement line is connected to the high-voltage capacitor bridge. The voltage divider ratio and phase error of the capacitive high-voltage voltage divider are calculated by reading the capacitance ratio and dielectric loss factor measured by the bridge. The theoretical voltage divider ratio of the capacitive high-voltage voltage divider can be obtained by the capacitance value of the reference capacitor C and Cx. The ratio error of the active voltage divider can be obtained by calculating the relative error.

Active high-voltage voltage dividers are usually connected in series with high- and low-voltage standard capacitors to form a voltage ratio standard for measurement. The traceability of high- and low-voltage standard capacitors can be verified or calibrated according to their technical specifications, while there are no relevant technical specifications for the traceability of active voltage dividers. The calibration method proposed in this paper can solve the problem of active voltage divider traceability; the calibration results have a large uncertainty problem caused by the large uncertainty of the capacitance measurement value of the high-voltage standard capacitor, and the measurement of the high-voltage standard capacitor needs to be studied. This study can provide a reference for the metrology department to calibrate the high-voltage active voltage divider, and provide technical support and reference for manufacturers to produce and develop such equipment.