Temperature Rise Test of High Precision RC Voltage Divider

作者： GOZ Electric 时间：2024-12-07 09:59:42 阅读：21

The equipotential shielding technology and temperature rise control technology scheme are used to design and develop 200 and 500kV high-precision RC voltage divider prototypes (see figure). The prototype adopts a modular cascade design concept. The primary voltage divider is composed of insulator components encapsulated with RC units in series. The number of insulator components in series is determined according to the rated voltage level. For example, at 500kV, the number of insulator components is 2, and at 200~250kV, the number of insulator components is 1.

To verify the effectiveness of the high-precision measurement technology described in this article, the following tests are conducted on the high-precision RC voltage divider prototype:

1) Comparison test of AC voltage divider ratio of high-precision RC voltage divider secondary voltage divider with and without shielding capacitor installed

2) Temperature rise test of high-precision RC voltage divider. The resistance and capacitance values of the high-voltage arm of the RC voltage divider are measured before and after the temperature rise test, the resistance/capacitance offset value is calculated, and the DC/AC voltage divider ratio test is conducted before and after the temperature rise test.

1 AC voltage divider ratio comparison test

Due to the limitations of the test equipment capacity and test operability, this test was only conducted on the 200kV high-precision RC voltage divider prototype. A 100kV AC phase voltage was applied to the high-voltage end of the prototype. In order to facilitate the evaluation of the influence of stray parameters on the measurement accuracy of the high-precision RC voltage divider, the test object was only the prototype voltage divider part, and the secondary signal acquisition system was not involved. The output voltage of the standard AC voltage divider and the prototype voltage divider was measured using an OI857II digital multimeter. The standard voltage divider model is TJF150-300, and the rated voltage is 150kV.

The test results show that the measured value of the additional error of the stray capacitance of the high-precision RC voltage divider with a rated measurement capacitance of 800pF and no shielding capacitor installed is 0.28%. After installing the shielding capacitor, the measured value of the additional error of the stray capacitance of the high-precision RC voltage divider is 0.05%. The measured value is close to the theoretical calculated value, which verifies the correctness of the mathematical model in this paper and the effectiveness of the equipotential shielding technology.

2 Temperature rise test

The design value of the resistance thermal current of the 200kV high-precision RC voltage divider prototype is 1mA. A 263kV DC voltage (1.25Um) is applied to the high-voltage end of the prototype. Wireless temperature sensors are arranged on the top flange and bottom flange surfaces of the voltage divider insulation to monitor the top and bottom flange temperatures of the insulator in real time. The temperature of each measuring point is recorded every 30 minutes.

The results show that before and after the temperature rise test, the measured values of the temperature rise of the top flange of the RC voltage divider and the change of resistance/capacitance value are basically consistent with the calculated values, which proves the effectiveness of the temperature rise calculation method proposed in this paper, and can be used to guide the main parameter design, key component selection and overall structural design of the RC voltage divider.

From the data, it can be seen that the change of the DC voltage divider ratio difference of the RC voltage divider caused by temperature rise is about 0.02%, and the change of the AC voltage divider ratio difference is 0.11%. When calculating the temperature rise in this paper, it is assumed that the temperature of the low-voltage arm component of the RC voltage divider is consistent with the ambient temperature. However, in fact, although the low-voltage arm components are arranged outside the insulator, their heat dissipation effect is better than that of the high-voltage arm components, the low-voltage arm components also have a working temperature rise, which plays a certain compensation role in the voltage divider ratio. Therefore, the DC/AC voltage divider ratio error of the RC voltage divider caused by temperature rise is smaller than the error caused by the change of resistance/capacitance value.

Conclusion

This paper studies the influence of stray capacitance and temperature rise on the measurement accuracy of the RC voltage divider, proposes a technical solution that can effectively improve the measurement accuracy of the RC voltage divider, and compares and analyzes the transmission principle and error influence of the traditional RC voltage divider and the high-precision RC voltage divider. Based on the equipotential shielding technology and temperature rise control scheme, a high-precision RC voltage divider prototype was designed and developed, and the effectiveness of the high-precision measurement technology and temperature rise algorithm was verified through measurement performance comparison tests. The technology is of great significance for guiding the main parameter design, key component selection and overall design of the RC voltage divider.

For the first time, the equipotential shielding technology using RC circuits was proposed and successfully applied to the development of a high-precision RC voltage divider prototype, which improved the measurement accuracy of AC signals of the traditional RC voltage divider by 2 measurement levels.

In view of the problem of temperature affecting measurement accuracy, different from the traditional passive heat dissipation idea, an innovative technical solution was proposed and implemented to reduce the thermal power of the RC voltage divider by optimizing the design of the main electrical parameters, reducing the temperature rise by several times and effectively improving the measurement accuracy.

Limited by the current test methods and conditions, it is impossible to accurately test the surface temperature of the high and low voltage arm resistor/capacitor components of the RC voltage divider during the test, and it is impossible to accurately optimize the temperature rise calculation method. The calculated value of resistance/capacitance change derived from the flange temperature data of the RC voltage divider and classical heat transfer theory is close to the measured value, which provides a new idea for the main parameter design of the RC voltage divider for engineering and the selection of RC/capacitance components for products.