Calculation Method of Electric Field Intensity for AC Crossing Transmission Lines

More attentions are paid on electromagnetic environment with higher voltage level for transmission lines.At present,the calculation method for electric field intensity of AC transmission line,which is a two-dimension model,apply to single transmission line.This kind of typical method in two-dimension can calculate electric field intensity in infinite boundary.Electric field intensity calculation of crossing transmission lines requires three-dimension model,however,there is on famous analytic method to calculate it in three dimension space.Usually numerical method is proposed to reach the conclusion for finite area.Some commercial software based on finite-element method,like ansys,can calculate electric field intensity in three-dimension space with definite boundary condition and solution region.For ansys,the computational accuracy depends on three factors,the boundary condition,the solution region and the subdivision of grid.It is required large solution region and small computational element if no accurate boundary conditions.That means more elements,more computational nodal and low computational speed.To solve this problem,the boundary condition is necessary.In this paper,two particular kinds of line charge are defined in three dimension and two formulas of line charge are deduced to calculate electric field intensity of unlimited long straight transmission line.For crossing transmission lines,it is assumed that two transmission lines interact each other in proximity area.As far distance,the interaction between crossing transmission lines is feeble.So the boundary condition can be achieved in such method: first the output of coordinates of each nodal in solution region is obtained from ansys after meshing;then each nodal of electric field intensity in three-dimension section can be calculated with these two formulas;finally the electric field intensity are input into simulation software as the boundary condition.For explicit boundary,the solution region can be deceased as well as the calculation speed.The comparison of simulation results and measurement results demonstrates this method applies for project.Additionally,electric field intensity with different height and phases are calculated by this method.The results indicate that the electric field intensity of crossing transmission lines near ground can be declined by rising the height of two lines and arranging the phase properly.