Experimental Study On The Effect Of Humidity On The Electromagnetic Environment Of HVDC Transmission Line In High Altitude Area

Along with the development of the extra HVDC power transmission in China,now more and more HVDC transmission lines have been put into operation.The electromagnetic environment parameters of transmission lines have become an important technical problem to be considered in the design,construction and environmental impact assessment of transmission projects.But our country has a vast territory,the west are high altitude area,the meteorological characteristics of the high altitude area are quite different from the plain area.The influence of humidity on electromagnetic environment must be considered,when constructing a DC transmission line in the high altitude.In this paper,using the DC simulation test line segment which is set up on the altitude 3400 and altitude 4300,three kinds of electromagnetic environment parameters are measured,including the total electric field at ground level,audible noise,radio interference,and study the effect of humidity on the electromagnetic environment of DC line at high altitude.In the paper,first analyses the measurement results of the electric field at ground level.Analysis results show that with the increase of altitude,the electric field at ground level increases gradually.When the humidity changes,only changes the size of the electric field at ground level,but does not affects its distribution characteristics.With the increase of humidity,the electric field at ground level increases gradually.Further,study the effect of humidity on the corona inception field strength of the conductor.The corona inception field strength decreases with the increase of humidity,then use the least square method fitting the relationship between the field strength and humidity,Used to estimate the electric field at ground level of transmission lines under the different humidity in high altitude area.Combining the example,in the case of meeting the national environmental protection limits analyses the minimum height of DC transmission line under different humidity in high altitude area.Last,analyses the measurement results of audible noise and radio interference.Analysis results show that with the increase of humidity,the audible noise of DC transmission line in high altitude gradually decreased;but the radio interference increases with the increase of humidity.Through the research of this paper,we can obtain that the influence of humidity on the electromagnetic environment of the DC line in high altitude area and can provide valuable basic data for the fine design of DC transmission lines in high altitude area.