| Corona phenomena on transmission line can bring serious harm to the operation and safety of power transmission lines,which is issues need special attention of the designer and operation department of power grid.At home and abroad,lots of researches have been carried out into corona of conductors,but mainly focus on the influence of atmospheric parameters,like high altitude,rain,fog,temperature and humidity,on the corona inception voltage and the electromagnetic environment.Nevertheless,researches of the influence of rain and fog on conductor corona noise,corona loss,corona discharge magnitude,and new T-type wires are rarely reported.Besides,the methods to measure audible noise,corona loss and corona discharge are not clear enough,and these conductor corona effects are research focuses for the design of UHV transmission line.Consequently,this work is expected to promote the corona discharge phenomenon and mechanism under rain and fog condition,providing reference to the design of transmission line in the rain or fog condition and for the application of T-type wire in china.This paper combines methods of experiments,theoretical and simulation analysis,via arrange simulation rain facilities in corona cage,single T-type conductor JRLX/T-310/40 is used for corona experiments under dry and rain conditions,and conductor LGJ 300/40 is employed for comparative test,which have the same diameter.In addition,an ultrasonic vibration fog generator is used to produce salt fog,experiments were carried out on the smooth stainless steel pipe with a diameter of 8 mm and on the conductors LGJ 35/6 and LGJ 80/30 in a corona cage,meanwhile,ultraviolet imager,partial discharge detector,sound level meter and oscilloscope are adopted to observe and record corona discharge phenomenon under different conditions.Analyzing the impact of conductor type,ac electric field intensity,fog conductivity and rain on trend of the conductor corona onset voltage,corona loss,corona discharge intensity and audible noise comparatively.The main results are as follows:(1)Compared with dry condition,conductor corona onset voltage,audible noise coronaloss of rain process is severer,the corona loss and the number of ultraviolet photonsshare the same trend with the applied voltage gradient,both grow rapidly beyondthe corona onset voltage.After the formation of water droplets which are attached tothe wire,the distortion of the electric field become more significant,transmissionline is more prone to form corona,and corona onset voltage is lower than before.(2)Rainfall rate has a significant effect on the conductor corona characteristics,thecorona characteristic is obviously deteriorated with the increase of the rainfall ratewhen the rainfall rate is at a lower level.On the other hand,as the rainfall rateincreases to a certain extent,the increase of corona onset voltage,corona loss andaudible noise become saturated gradually.(3)Under the same electric field intensity,the audible noise values and the corona lossof T-type wire are lower than those of the steel reinforced aluminum conductor,whether it is in rainfall process or dry condition,and the corona characteristics ofT-type wire is better,which is of great significant for the design of transmission linein the rainfall process and for the promotion of T-type conductor in china.(4)When the surface of the conductor is saturated with water droplet,the fogconductivity has a great influence on the corona discharge intensity.The coronadischarge intensity increases with the increase of the fog conductivity at the sameelectric field intensity.And Corona discharge magnitude increases with the increaseof electric field intensity,then saturate with the electric field strength increases to acertain extent. |
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