Design And Detection Of Power Frequency Electric Field Sensor For Safety Early Warning Of Power Transmission And Distribution Operation

The electric field environment near the high-voltage transmission line and substation is complex.During the on-site operation,the operator has an electric shock accident.Therefore,it is of great significance to analyze the electric field distribution characteristics near the transmission line and the substation.The research and development of electric warning equipment has also received more and more attention.This paper mainly studies the distribution characteristics of power frequency electric field near the high-voltage transmission and transformation lines and the design and detection of the power frequency electric field sensor,which provides assistance for the development of the near-electric safety warning device.The main research contents of this paper are as follows:1.Using the calculation principle of the analog charge method,the mathematical model of the power frequency electric field calculation of the high-voltage transmission line is established,and the electric field distribution at different heights of the 500 kV high-voltage transmission line is calculated,and the electric field distribution is multi-peak.2.Using COMSOL software,the electric field intensity distribution near the high-voltage transmission line and the electric power tower in the form of single-circuit horizontally wired line with different voltage levels and 500 kV voltage level in different lines of the same tower is simulated.The’eight’shape of different angles radiates to the ground,and the electric field intensity distribution curves are also hump-shaped.The electric field distribution simulation app of two high-voltage transmission lines of single-circuit and same-circuit double-circuit is developed,which improves the efficiency of electric field distribution simulation of high-voltage transmission lines.3.The overall model of a 220 kV substation is simplified.The electric field intensity distribution of the 1.7 m high level surface in the substation is analyzed by COMSOL simulation.The area with large electric field strength is mainly concentrated in the 220 kV switchyard.The electric field intensity distribution curve fluctuates and the maximum electric field strength on the patrol path in the 220 kV switching field is close to 11 kV.4.In order to reduce the influence of edge effect,a power frequency electric field sensing unit with equipotential ring structure is designed.Through the simulation optimization analysis,the structural parameters of the power frequency electric field sensing unit are determined.And the sensing unit is summarized.that the mathematical relationship between the width of the bit loop and the radius of the sensing unit:k=8.35r^-0.3584.Measure and analyze the physical characteristic parameters（such as capacitance,loss factor,impedance and phase）of the sensing unit with different sampling capacitors,and the static characteristics（such as linearity and sensitivity coefficient）under the uniform electric field of the power frequency.According to the test results and the design requirements initially selected the 5-5 sensing unit with a structure parameter of 32×32×1.6mm and a sampling capacitor of 3.3nF as the electric field sensing component of the power frequency electric field sensor.5.The signal processing circuit of the power frequency electric field sensor is designed,including voltage follower circuit,signal differential circuit,50 Hz band pass filter circuit and full wave rectification circuit.The designed circuit module is simulated and tested by Multisim.The results of the hand-welded sensor signal processing circuit test verify the correctness of the circuit.6.According to the national standard calibration of power frequency electric field measurement,the performance indexes of the power frequency electric field sensor are calibrated.The linearity of the primary selected 5-5 sensing unit is±1.3352%,but the range is 0¹20 kV/m.After evaluation,the 5-7 sensing unit is selected as the electric field sensing unit of the power frequency electric field sensor.After calibration,its performance indexes have met the design requirements.Its linearityγ_L is±0.9003%,sensitivity is 0.0187 V/(kV·m^-1),accuracyγ_E is 1.5259%,and range is 200 kV/m.The measured performance of the calibrated power frequency electric field sensor and the EHP-50F low frequency electromagnetic field analyzer are compared.The results show that the relative error of the power frequency electric field sensor measured in this paper with EHP-50F is less than 6%,which has a high correlation.7.A method for identifying the direction of the spatial field source based on the multiple power frequency electric field sensors designed in this paper is proposed.