Measurement of super high voltage transmission line electric field effecting on the environment

Alterative current transmission lines with voltage of 500 kV are the most powerful source of electro-magnetic non-ionizing radiation. The investigation of radiation effect on technical personnel began in Russia as early as 1953 after the construction of the first 220 kV transmission lines, when the first signals of health worsening of workers appeared. The research results which are presented in this report was carried out by the authors during the period from 1997 to 2007 on different enterprises of main network systems of the Ural and Western Siberia Russia. The experimental investigations were carried out near functioning line of 500 kV, in a zone of the greatest electric field intensity. The method of passive experiment was used during the research. It assumes the measuring by in advance planned combinations of factors which may influence on the considered parameters. At the first stage it was the parameter the electric field intensity (50 Hz frequency). The factors which theoretically can influence on the value of electric field intensity are the following: Voltage of transmission lines of 500 kV; Load current with position of its influence on heating of the transmission line in compare to air temperature and change of line sag over the ground; Atmospheric effects (including air temperature, absolute and relative air humidity, wind speed, speed pressure of wind). The correlation analysis was made by using of received experimental results. According to the results of the correlation analysis, it was made a conclusion that the greatest influence on the amount of electric field intensity under transmission line is made by the factors that can change the line sag and consequently the distance from current-carrying parts to points of measurement. Besides, the distance from current-carrying parts to ground surface is influenced by the change of relief where transmission lines run. Local rising and lowering of the ground level under this part of transmission line may lead to considerable change the electric field intensity, bias area of maximum intensity from line centre, and distort the symmetric picture.