Study On Measuring Method And System Of Transmission Line Voltage By Electric Field Integration

In the power system,the accurate measurement of line voltage is very important for electric energy calculation,Overvoltage On-line Monitoring and relay protection.At present,the method of non-contact measurement of transmission line voltage based on field sensor has been widely studied.The calculation method based on the inverse problem of electric field has difficulty in solving the problem,and it is difficult to calibrate the problem,while the electric field integration of Gauss algorithm saves the problem of the location of the integral node,and the precision needs to be improved.In view of this,a method for obtaining the transmission line voltage based on the spatial electric field integration of the D-dot electric field sensor is proposed,and the differential D-dot electric field sensor and the electric field integral method voltage measurement system are designed.The feasibility of the electric field integration method is proved by the Chebyshev integral algorithm.The system voltage measurement provides a new method.The main work of this paper includes the following aspects:(1)Integration path selection and integral interval segmentation optimization.Through the conservation analysis of the space electric field of the transmission line,it is concluded that the integral result is independent of the selection of the integral path.The feasibility of the electric field integration method is illustrated,and the vertical line on the vertical ground of the transmission line is established as the integral path,and the formula of the Chebyshev algorithm is pushed and the electric field distribution on the integral path is put forward.The curve is piecewise linearized,and the integral node position and integral weight of each segment are obtained.Because the location of the node and the integral weight are only related to the D of the transmission line to the ground distance,the electric field integration formula of the voltage grade transmission line can be quickly obtained by bringing the ground distance D of different voltage grades into the relevant formulas and forms in the paper.(2)Accuracy of the integral algorithm verified by simulation.The finite element simulation model of the horizontal arranged transmission line is established by Maxwell software.The feasibility of the electric field integration of the Chebyshev algorithm is verified by the simulation data.The integral interval is optimized by adjusting the value of the piecewise factor K,and the location of the optimized node is more suitable for the insulation of the sensor.The accuracy of the Chebyshev algorithm applied to the electric field integral of transmission line is improved.The simulation results show that the integral error is less than 1.8%.(3)Design of the measurement system.In view of the characteristics of the electric field integration,a dual differential D-dot electric field sensor is designed.Through the design of multi-channel synchronous acquisition circuit,the output electric field signal of the sensor node is collected.The real-time calculation,waveform display and analysis of the electric field integration are completed in the LabVIEW software.(4)Electric field integration test of the transmission line.A three phase horizontal arrangement transmission line test platform is built,and the integration test is carried out according to the location of the integral node of the Chebyshev integral algorithm to place the D-dot sensor.The electric field data collected by D-dot sensor is calculated and fitted by LabVIEW software integration program,and the real-time waveform of the conductor voltage to be obtained is obtained.Through calculation,the distortion of the waveform is small,and the error of the integral amplitude is less than 2%.