The significance of 1200kV lightning impulse voltage standard measurement system

Author： GOZ Electric Time：2024-08-06 09:18:42 Read：13

    At present, the rated voltage of the national metrology standard system required for traceability of impulse voltage measurement system is only 700kV, which cannot meet the traceability requirements of UHV electrical appliances of 3500kV and above. The structure of the developed 1200kV resistor divider was analyzed, and the performance test and improvement of the established 1200KV impulse voltage weight measurement system were carried out. The system was compared and calibrated with the existing 700kV impulse voltage national standard measurement system within the voltage range of 700kV, and the linearity experiment was carried out within the voltage range of 700kV to 1200kV. The uncertainty of the 1200kV standard impulse voltage measurement system was evaluated. The evaluation results show that the test voltage, wavefront time and half-peak time measurement errors of the developed 1200 kV lightning impulse voltage standard measurement system are within the allowable range of the international standard IEC60060 and the national standard CB/T 16927, and the rated voltage level of my country's national standard impulse voltage measurement system is increased to 1200 kV.

    Keywords: impulse voltage generator; UHV electrical appliances; uncertainty assessment; metrological standards; lightning impulse; comparison calibration

1 Introduction

    Impulse high voltage test technology is widely used in the fields of power equipment performance testing, aircraft, aerospace systems, etc. The value of impulse high voltage is closely related to the safety, reliability and economic design of the equipment under test, and requires accurate measurement and traceability. With the development of domestic high voltage technology, the rated voltage of some impulse voltage generators and measurement systems for UHV tests has reached 7200kV, and the rated voltage of the calibration system required for its calibration has reached more than 1000kV.

    The impulse voltage divider is the main body of the impulse voltage measurement system, which converts the lightning impulse into a low-voltage signal that can be measured. The impulse voltage divider mainly includes a resistor voltage divider, a capacitor voltage divider, and a resistor-capacitor voltage divider. The resistor voltage divider is wound with a small temperature coefficient and high resistivity Kama wire without induction. It has the advantages of good response characteristics, high temperature stability and long-term stability. It is very suitable for the measurement of fast pulses. Therefore, it is also often used as a standard voltage divider for various national metrology institutes (NMI). However, since the energy consumed by the resistor divider is proportional to the square of the applied voltage, it will generate heat when working. Therefore, when the voltage level is too high, the resistor wire is easy to burn out. Secondly, with the increase of voltage level, the stability and dynamic characteristics of the resistor divider are greatly affected by stray parameters. These factors limit the resistor divider from achieving the same high voltage level as the resistor-capacitor divider. According to the information provided by the key comparison database (KCDB) of the National Bureau of Metrology (BIPM), many national metrology institutes have established impulse voltage standard measurement systems and formed corresponding calibration and measurement capabilities (calibration and measurement capability, CMC), but only a few have a rated voltage of more than 1000kV.

     The German Federal Institute of Physics and Technology (PTB) has established an impulse voltage CMC with a rated voltage of 1500 kV and a measurement uncertainty of 0.5%; the National Metrology Institute of Australia (NMIA) has established an impulse voltage CMC with a rated voltage of 1000 kV and a measurement uncertainty of 1%. In China, the National High Voltage Metering Station and Xi'an High Voltage Technology Research Institute have established a 500kV impulse voltage measurement system with a measurement uncertainty of 0.5%. The China National Institute of Metrology has established a 700kV impulse voltage national standard measurement system and formed the corresponding CMC, with the CMC of the test voltage reaching 0.5%. In 2018, the China National Institute of Metrology represented China in the international comparison EurameL.EM-S42, and the results were published in BIPM KCDB and Metrologia journals. However, the current development of power grids and power equipment has put forward new calibration requirements for impulse voltage measurement systems at higher levels, and it is urgent to establish an impulse voltage standard measurement system with a rated voltage exceeding 1000 kV and international equivalence recognition.

    After relevant research and design, a 1200kV impulse voltage measurement system was designed, and the measurement system was verified through experiments. The following conclusions were drawn:

1) The waveform of the system response was obtained through square wave testing, which was convolved with the standard lightning waveform, and the measurement error caused by the system was calculated by software. The results showed that the comparison errors of the test voltage U, wavefront time T half peak time T, of the 1200kV impulse voltage measurement system were within a reasonable range. The comparison experiment was carried out with the national standard lightning impulse voltage measurement system within 700kV. From the comparison results, it can be concluded that the waveform measured by the 200kV impulse voltage measurement system is generally consistent with the waveform collected by the standard measurement system, and the indication error is within the allowable range of IEC60060 and GB/T16927. According to the experimental results of linearity, it can be seen that the ratio error of the test voltage and charging voltage measured by the 1200kV impulse voltage measurement system is within the allowable range of the national standard, which verifies the linearity of the measurement system.

2) The uncertainty of the 1200 kV standard impulse voltage measurement system was evaluated. The relative expanded uncertainties of the test voltage, wavefront time and half-peak time were 1%, 2.7% and 1.7%, respectively, with h = 2.