Research On Three-Dimension Al Power Frequen Cy Electric Field Intensity Of Parallel And Cross-Crossing High Voltage AC Transmission Lines With Different Voltage Levels

With the development of economic construction,the scale of power grid is expanding,and the long-distance and large-capacity high-voltage AC transmission lines are developing rapidly.However,due to the restriction of land corridor,there are inevitably parallel or cross-over situations of different voltage levels of high-voltage AC transmission lines.In the previous research,some scholars have carried out a more detailed study on the power frequency electric field intensity in parallel with power grid of the same voltage level,but few people have studied the power frequency electric field intensity in parallel or cross-over of power grid of different voltage levels.In this paper,the theory and prediction of power frequency electric field intensity for different voltage levels of high voltage AC transmission lines are studied.It can provide reference methods and basic data for future power transmission and transformation engineering design and environmental impact assessment,and has important engineering application value.On the basis of previous studies,taking the 330kV tower type of UHV as an example,the influence of catenary equation and typical meteorological parameters on sag of transmission line is discussed and analyzed.At the same time,the influence of meteorological parameters,horizontal spacing,height of conductor to ground,distance between phases,type of conductor and number of split conductors,distance between splits,single-loop conductor layout and phase sequence arrangement of double-loop conductors on power frequency electric field intensity are analyzed,and valuable results and conclusions are obtained.A three-dimensional electric field intensity prediction mathematical model for different voltage and high voltage AC transmission lines under parallel conditions is established.Taking 750 kV and 330 kV power grid parallel typical projects as examples,the power frequency electric field intensity prediction research is carried out,and the accuracy and reliability of the model are verified by comparing with the measured data.By analyzing the distribution of power frequency electric field intensity under different parallel conditions of 750kV and 330kV,the safe distance of power frequency electric field intensity reaching the public exposure limit at the lowest design height is obtained.The results also show that the reaching area increases gradually with the increase of parallel distance.The reaching distance outside side conductor is mainly related to tower type.Therefore,it is suggested that the design and construction of transmission line should be carried out.The power frequency electric field intensity can be reduced by enlarging parallel spacing and selecting tower type and location reasonably.A three-dimensional electric field intensity prediction mathematical model for high voltage AC transmission lines with the same level of voltage is established.Taking a typical 750kV tower type as an example,the three-dimensional electric field intensity distribution under typical con ditions such as single-circ uit cross-over,double-circuit cross-o ver on the same tower,single-circuit cross-over on the same tower and double-circuit transmission lines is studied.The cross-over time of single-circuit cross-over is analyzed and summarized.The influe nce factors of angle and crossover point position on the power frequency electric field intensity under line are obtained,and valuable results and conclusions are obtained,which can provide reference for the electrom agnetic environmental impact assessment and treatment of transmission lines when crossover occurs.