Self-calibration Method Of Non Contact AC Voltage Measurement

Voltage parameter is not only an important monitoring object on the device,but also an important perception on smart grid nodes and lines.Accurate monitoring of voltage signal can provide important information for power system energy measurement,smart control and relay protection,and has high research value.At present,traditional contact voltage measurement methods need to remove the insulation layer when measuring the actual line voltage,which will destroy the transmission line,and the operation close to the high voltage source will bring some security risks to the surveyors,which can no longer meet the development needs of today’s smart grid.Non-contact voltage measurement can solve the limitations of the traditional contact voltage measurement methods mentioned above,but the accuracy of such measurement methods is closely related to the coupling capacitance voltage ratio,which is easy to be affected by environmental factors and leads to the decline of measurement accuracy,and has not been widely used in production practice.Therefore,the application of non-contact voltage measurement in distribution line measurement is studied,and a non-contact AC voltage measurement method with self-calibration is proposed to improve the accuracy of non-contact voltage measurement.The main contents of this article are as follows:1.A review was conducted on existing non-contact AC voltage measurement methods,summarizing the advantages and disadvantages of common non-contact voltage measurement methods,such as stray capacitance voltage measurement,photoelectric conversion principle measurement,and measurement using inverse piezoelectric effect.Factors affecting the accuracy of non-contact measurement were also explored.Through comprehensive analysis,it can be found that due to the susceptibility of voltage divider to environmental factors,the capacitance value changes.Therefore,the voltage divider model formed between the tested circuit and the sensor is unstable,which can easily affect the measurement accuracy.Based on this article,a non-contact AC voltage measurement self calibration method is proposed,which utilizes the self calibration principle to eliminate measurement errors caused by unstable voltage ratio,in order to improve measurement accuracy..2.Based on the principle of voltage dividing,the AC voltage measurement model of transmission line is equivalent to the three-capacitance coupled voltage dividing model.The relationship between the primary and secondary capacitance and the voltage dividing ratio of the sensor is analyzed,and the theoretical basis is used to explain why the measurement accuracy of non-contact measurement method based on the principle of space capacitive voltage dividing is affected by ambient stray parameters.In order to reduce the interference caused by stray parameters to the measurement,the self-calibration measurement principle is proposed based on the system identification theory.The self-calibration mechanism of non-contact AC voltage is deduced in theory,and a systematic measurement method is formed.The feasibility of improving the non-contact measurement accuracy of AC voltage by the self-calibration mechanism is demonstrated.3.Under the theoretical support,a complete set of non-contact AC voltage self-calibration measurement system is implemented,and an overall measurement system composed of three main modules,namely,coupling capacitance probe,operational amplification conditioning circuit and data acquisition device,is established.The structure of the measuring probe is designed,the specific probe size is determined by using the finite element simulation software,and the probe prototype is made by using 3D printing technology.The back-end conditioning circuit is designed,and the system functions are implemented by operational amplifier circuit.The correctness of the circuit is verified by simulation,and a PCB circuit board is made.In addition,a special data acquisition card for this system is customized,and an overall measurement system is finally established.4.In order to verify the feasibility and practicability of the methods proposed in this paper,an experimental platform for non-contact AC voltage measurement is set up to collect and reproduce the voltage waveform.The test results show that the methods proposed in this paper can restore the measured voltage waveform,with some unavoidable noise interference and phase delay.The overall relative error is less than 2%,and the phase error is less than 4 degrees.This method is summarized and the future research direction is prospected.