| The power-frequency electric field measurement technology, which has alwaysbeen valued by the power industry, is an important mean to determine the failure state ofelectric transmission line and the safe distance of live working. Based on the idea ofdetermining the safe distance with the electric field over-limit and by combing thewireless data transmission technology and the electric field measurement technology,this paper developed an warning instrument for the group-type of HV electric fieldmeasurement and safe distance based on wireless transmission. The combined formadopts a master and multiple slaves, in which the slaves are used to conduct real-timeand effective monitoring of power-frequency electric field near the HV transmissionline and directly display the figures. In case of exceeding the safe distance and electricfield over-limit, the slaves give an alarm and send the alarming signing to the master.The master keeps the real-time wireless communication with the slaves and conductsthe real-time wireless monitoring to the slaves, thus realizing the dual monitoring of siteand command and preventing the electric safety accident.Elaborate the electric field measurement method of electrical theory and deducethe mathematical principle of alternating electric field measurement of1D sphericalsensor, thus laying the theoretical foundation for the design of electric field sensor;explain the reason of electric field measurement with the parallel-plate sensor, instead ofthe spherical sensor, analyze the theoretical feasibility of electric field measurement,and complete the material design of capacitive parallel-plate sensor; introduce the safedistance determination method of transmission line, analyze the feasibility of the safedistance of the live working of the indirect characterization of electric field strength,propose the idea of determining the safe distance based on electric field over-limit, andobtain the critical field of the safe distance of transmission line at the voltage of35~750kV through simulation.Introduce the overall design and working principle of system, analyze the keyhardware design of signal processing circuit, power switch circuit, human-computerinteractive circuit and wireless communication module and select the proper electroniccomponent to complete the hardware design of system; with Keil4as the softwaredevelopment platform, design the analog-to-digital conversion, LCD, master and slavecommunication, electric field over-limit alarming and other programs, complete the system program debugging and finally complete the overall design of group-type of HVelectric field measurement and safety distance alarm system based on C8051F410SCM.Conduct linear calibration test of power-frequency electric field of sensor andsuccessively conduct the comparative test of electric field measurement with the slaveof group-type system in the single-phase transmission conductor experiment platformbuilt in the laboratory and on the site of Chongqing Rongchang500kV Hongbantransmission line I by taking the advanced electromagnetic field measuring instrumentEFA300as the reference standard; meanwhile, conduct a working performance test onthe site of500kV transmission line to verify the the alarm performance and the wirelesscommunication performance for group-type system.The test results show that the capacitive parallel-plate sensor can be used for thepower-frequency electric field measurement and the scale factor is11kV m-1mV-1under the action of power-frequency electric field. The designed of group-type of HVelectric field measurement and safety distance alarm system have good performance.The relative measurement error of slave is within10%and can give an alarm in case ofelectric field over-limit, the master can receive the real-time date and the alarm signalfrom the slave at the same time. The whole group-type system have a stable work, thusmeeting the needs of power engineering. |
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