Study On On-line Monitoring And Status Evaluation Technology For Insulators Of UHV Transmission Line

Due to the inverse distribution of energy resource and load in China,with the rapid development of national economy,the development of UHV power transmission is the future direction of China's power transmission.As an important electrical equipment of UHV transmission lines,the insulators are used in a large amount with a high accident rate,the pollution flashover of insulators is a great threat to the safe and stable operation of transmission lines.Therefore,it is necessary to study polluted discharge law of insulators,design the insulators on-line monitoring system to complete the real-time assessment of insulators pollution degree,and prevent insulators' faults,improve the operation reliability of transmission lines.In this paper,four stages of insulators' pollution flashover are described at first:pollution deposition,wetting,producing dry belt and local arc,local arc develop to be flashover.The arc model for the flashover process at AC and DC voltage was analyzed,the maximum pulse amplitude of the leakage current,temperature and relative humidity of insulators were determined to be characteristic values for the online monitoring of insulators.As there are some shortages of the traditional monitoring technology,such as heavy workload,difficult to achieve real-time monitoring,etc,radio frequency identification(RFID)technology is a kind of wireless data transmission technology which achieve non-attach target recognition by radio signal,in this paper,an on-line monitoring system based on RFID technology is presented.In the traditional RFID system,integrated circuit(IC)tags is used,however,it is difficult to work in harsh environments,such as high temperature,strong electromagnetic etc,So anti-interfrence SAW tag instead of the IC tag in this paper.SAW-RFID system is used to realize online monitoring temperature and humidity of insulators,this paper describe the design principle of SAW tags in detail:by comparing different kind of piezoelectric performance parameters to determine the piezoelectric substrate material;The frequency response and impedance characteristics of the IDT are analyzed by ? function model and equivalent circuit model,and then set proper parameter value.The circuit model of the reflectors is analyzed,the design principle of the reflectors is defined,and the parameters are calculated;In order to achieve the performance of the antenna,a printed dipole antenna is adopted in this paper,and antenna arm is folded to minimize the size,thus return loss and smith chart of antenna areobtained by HFSS.Communication test and performance test for SAW tags are carried out by RFID tester,then the test of the SAW-RFID online monitoring system were completed,and the data acquisition,transmission,storage of the characteristic values were achieved.Finally,build an improved three layer fuzzy SOM(Self-Organizing Feature Map)neural network,the neural network was trained with the data from the artificial pollution experiment,and the insulators' pollution status assessment algorithm based on fuzzy neural network was proposed,experimental data are also used to test the performance of the SOM neural network,the results indicated that the assessment algorithm has high accuracy and good real-time performance.This paper design an online monitoring system of insulators based on SAW-RFID technology,and the insulators' pollution status assessment algorithm was proposed,which can reflect the pollution condition of insulator surface real-time,and provide reference for the operation and maintenance of insulators,improving the reliability of the safe operation of UHV transmission lines to a certain extent.