Push-Pull AC/DC Electric Field Sensor And Its Application Technology

With the continuous development of environmental assessment technology for power transmission and transformation projects,the problem of electric field testing and evaluation is imminent.At the same time,the scale of China's power grid construction is expanding,the transmission line corridors are more crowded,and high-voltage transmission lines are adjacent to residential buildings,AC and DC lines and corridors.More and more common,in order to ensure the personal safety of the staff and ensure the living environment of the residents,it is necessary to accurately and accurately measure the electric field in real time,to judge the safety state of the transmission line,the electromagnetic environment and the insulation state of each power equipment.Therefore,designing an electric field measurement suitable for a variety of environments is of great significance.The paper first introduces the current research status of various electric field sensors,and elaborates the advantages and disadvantages of various types of sensors.On this basis,the measurement principle and structure of field-grinding electric field sensors are elaborated.Aiming at the shortcomings of traditional field-grinding sensors in electric field distortion and grounding shielding principle,a new structure of push-pull AC/DC electric field sensor based on induced charge principle is proposed,which mainly includes four parts: the first part is the sensing piece and the shielding piece.Structural design,selection of fabrication materials,preparation of the model;the second part is the design and manufacture of the coupling;the third part is the improvement of the grounding shielding principle to eliminate the error caused by the ground potential elevation;the fourth part is the motor The selection and design and manufacture of the sensor housing.At the same time,the sensor adopts dual signal output,which improves the utilization rate of the sensing chip on the one hand,and the electrostatic field and the alternating electric field at the same time for the corresponding processing of the output signal.This paper designs the corresponding electric field measurement hardware circuit,including: analog signal extraction circuit,multi-channel selection amplifier circuit,signal conditioning circuit,data acquisition circuit,central control circuit,communication circuit,power supply circuit,temperature and humidity acquisition circuit.In this paper,a high-impedance operational amplifier CA3140 is used to design a two-way signal extraction circuit.A precision full-wave rectifier circuit is designed with a precision op amp OP07 to ensure the extraction accuracy of weak signals.At the same time,the above hardware is welded and debugged in the laboratory,and the upper computer software and the lower computer software system based on LabVIEW are designed to realize the comprehensive control of the measurement system.According to the requirements of GB-T12720-1991,the test under the uniform electric field generating device shows that the push-pull AC/DC electric field sensor designed in this paper has good linearity,between 10V/m-150V/m measurement range.The system error is about 10%,and the system error is about 3% between 150V/m and 100kV/m.After calibration,meet the needs of engineering electric field testing.