Research On Accumulation Mechanism And Detection Technology Of Insulator Pollution For Transmission Lines

With the continuous construction of ultra-high-voltage(UHV)transmission lines,they have to pass through various complex contaminated areas such as villages and suburbs,which will be prone to be polluted.Then the large number of particles will be deposited on the insulator arranged on overhead lines,resulting in the formation of pollution layer.Under the influence of external factors such as fog and drizzle,the pollution layer is prone to moisture,resulting in a decline in the electrical performance of insulator.It may cause insulator flashover,which seriously threaten the safe and reliable operation of the power grid.The accumulation is the fundamental cause of insulator flashover,and the hot issues around the world are to deeply study the formation mechanism and effectively detect the pollution degree.Therefore,the stress and energy balance of polluted particles are mainly studied,starting from the formation process of pollution in the paper.Then the pollution growth model of insulator is further improved by considering the removal of particles after collision.In addition,the technology of non-destructive detection using optics is introduced into the field,which makes up for the existing shortcomings.Specific contents include:(1)The movement process of particles plays an important role in in-depth research on the mechanism of fouling.Therefore,the characteristics of the flow field and polluted particles are analyzed,and the trajectory equation in the flow field is established to obtain the collision velocity.Then the particles collision with insulator and pollution layer are studied respectively,and the conversion of two collision forms is realized through the deposition rate.The collision mechanism between particles and insulators is further revealed by taking the removal of deposited particles into account during the collision.(2)In the validation of the pollution growth model,firstly,the model is established to simulate particle motion in the flow field,and the collision velocity between particle and insulator is solved by COMSOL software.Then the velocity is introduced into the growth model and the pollution on insulator surface is calculated.Finally,a fouling of lxy-160 insulator is simulated in the test platform to verify the accuracy of the model.The results show that the relative error between theory and test is 20.1% ～ 23.3%,which indicates that the model can reflect the actual contamination degree of insulator to a certain extent.In addition,the verified model is used to systematically study the characteristics of uneven distribution of pollution on the insulator,and the influences of wind speed,particle diameter and end effect are analyzed.The results show that the increase of wind speed and particle diameter aggravates the uneven distribution of pollution,and the end effect makes the pollution degree at the top and bottom of the insulator string.(3)In order to realize non-destructive detection of surface pollution,the detection technology of transmission line is studied based on optical fiber sensing.The test of salt-ash density characteristic of optical fiber surface is carried out to analyze the relationship between light energy loss and ESDD,relative humidity and fouling times of the insulator surface.Then,a RBF neural network is proposed to convert the optical detection into traditional quantities.The network is trained and tested by using 320 randomly selected samples of artificial fouling test,and the feasibility of the model is verified by indicators,which are mean relative error,root mean square error and model efficiency.The mean relative error is 3.47%,3.20%,root mean square error is 4.14%,3.71%,and the model efficiency is up to 99%.(4)An online monitoring is an important method to obtain the pollution degree of insulators in real time.The system for insulator pollution is constructed using fiber optic salt-ash density,and the key technologies of the monitoring device are emphatically studied.Using solar energy and storage batteries,a low-power UPS is designed to ensure sustainable power supply for the monitoring device.The problem of data loss during transmission is solved based on compressed sensing theory.Then the monitoring system is tested on the platform of a 110 k V transmission line,and the practicability of the system is verified by comparing with the manual test results.The monitoring error of ESDD is 9.38%,and that of NSDD is8.36%.In the paper,the growth process and detection technology of pollution are studied for insulators on the transmission line,the analysis system of fouling characteristics is improved,and a new nondestructive detection method for pollution is provided,which has certain reference value for the configuration of external insulation of transmission lines and the development of anti-pollution work.