Research and design of a high-stability nanosecond resistor voltage divider

Author： GOZ Electric Time：2024-07-27 09:14:49 Read：13

Aiming at the overshoot phenomenon of the capacitive voltage divider in the process of measuring high-voltage pulse voltage, theoretical and experimental research on high-voltage pulse sensors and nanosecond pulse measurement systems is carried out to develop and manufacture high-voltage and high-stability nanosecond high-voltage pulse voltage dividers.

Firstly, through the modeling calculation and experimental research of the pulse resistor voltage divider, the law of the change of the distributed capacitance of the resistor voltage divider with the structural parameters of the resistor voltage divider is obtained, and the optimized structural parameters of the 60kV nanosecond pulse resistor voltage divider of this project are determined to be (Φ20 mm+4 mm)×(100 mm+20mm). Then, the circuit analysis is carried out to obtain the theoretical calculation formula of the response time of the nanosecond pulse resistor voltage divider. According to the design requirements of this paper, the resistance value of the nanosecond pulse resistor voltage divider is designed to be 500~1000Ω to meet the requirements. Affected by the skin effect, the high-frequency resistance is much larger than that at low frequency. The resistor voltage divider designed in this paper is used to measure the pulse voltage with nanosecond rise time. In order to avoid large errors in the resistor voltage divider when measuring high-frequency signals, thin film resistors are used as the high-voltage arm resistor and low-voltage arm resistor of the pulse resistor voltage divider.

Based on the above research on the key technologies of nanosecond pulse resistor divider, a nanosecond pulse resistor divider with a withstand voltage of not less than 60kV was developed. The high and low voltage arm resistors are installed in series on the coaxial structure tube core, and the outer shell is insulated with polytetrafluoroethylene.

Calibration of high-stability nanosecond resistor divider

The scale factor of the nanosecond resistor divider is calibrated by the scale factor transfer method under standard microsecond pulse, and compared with the scale factor of the divider under DC or AC steady state to verify the feasibility and rationality of the scale factor calibration method of the nanosecond resistor divider. The step response characteristics of the pulse resistor divider are tested using a nanosecond square wave generator with a rise time of 1ns, and the data are recorded using a Tektronix DPO3054 oscilloscope.

From the step square wave response of each sensor, it can be calculated that the step response time of the nanosecond resistor divider, P5100A, P6015A and PVM-1 high voltage probe are 1.06, 0.67, 1.22 and 3.80ns respectively. Among them, there is an obvious unreasonable difference between the response time of P6015A and its bandwidth (75MHz), and the step square wave response time of Polaris PVM-1 high-voltage probe is too large. Therefore, the P5100A probe is used in the subsequent calibration experiment.

The nanosecond resistor divider and Tektronix P5100A high-voltage probe have been calibrated and certified by China's third-party metrology center. Among them, the steady-state scale factor of the nanosecond resistor divider is 1020, and the average value of its dynamic scale factor is 1025 under the 1.2/50 us lightning pulse. It is concluded that the error between the static and dynamic scale factors of the nanosecond resistor divider is 0.49%, which supports the rationality and feasibility of calibrating the performance parameters of nanosecond sensors with high-precision bridges and step square wave responses. At the same time, in order to verify the rationality of the calibration of the scale factor of the nanosecond resistor divider, this paper conducts a horizontal comparison measurement with the calibrated P5100A high-voltage probe with a scale factor of 100.76 under the 1.2/50us standard lightning pulse and nanosecond pulse voltage.

The test results are as follows: Under 1.2/50us pulse voltage, the scale factor of the nanosecond resistor voltage divider is 1016.91, and the errors between its steady state and scale factors under nanosecond pulse are -0.30% and -0.79%, respectively. Under the action of nanosecond pulse voltage, the scale factor of the nanosecond resistor voltage divider is 1020.63, and the errors between its steady state and scale factors under 1.2/50us electric pulse are -0.062% and -0.43%, respectively. The absolute deviation between the scale factors of the nanosecond resistor voltage divider calibrated with the Tektronix P5100A high-voltage probe is only 2.10, and the relative error is about 2.00%0.

Based on the above test results, it can be analyzed that in the absence of nanosecond high-voltage pulse calibration source and nanosecond pulse standard, it is feasible to use microsecond standard source or microsecond standard voltage divider to calibrate the nanosecond resistor voltage divider. However, the nanosecond resistor divider must undergo a step response experiment to ensure that the response time or upper frequency limit of the resistor divider can meet the requirements for accurate measurement of nanosecond voltage pulses.

Output characteristic test results of nanosecond pulse power supply

In an SF6 gas environment, by adjusting the gas pressure of the two cavities and the charging voltage of the Marx circuit, nanosecond pulses with a rise time of 2.3ns±0.5ns, a half-peak time of 25ns+5ns, and an amplitude range of 10~60kV can be obtained. To obtain higher test accuracy, a Tektronix MSO54 oscilloscope (bandwidth 1GHz, sampling rate 6.25 GS/s) is used to measure the output waveform.

The nanosecond pulse circuit and its nanosecond pulse measurement unit constitute a nanosecond pulse power supply system. In order to evaluate the stability of the pulse power supply system, this paper selects 6 voltage levels within the range of 60kV and conducts 30 repeated discharge experiments respectively, and uses relative standard deviation to characterize the stability of the nanosecond voltage output. From the test results, it can be concluded that within the output voltage range of 10~60kV, the relative standard deviation of the nanosecond pulse output by the nanosecond pulse power supply system is no more than +1.5%. In view of the current situation that there is no nanosecond standard source and no nanosecond standard, the development of this high-stability nanosecond pulse power supply system has very important theoretical significance and application value for the research and standardization of nanosecond pulse calibration and measurement technology.