交流输电线路交叉跨越区域空间电场计算方法

Calculation Method of Electric Field Intensity for AC Crossing Transmission Lines

随着输电线路电压等级的升高,电磁环境问题受到越来越多的关注。目前的交流输电线路地面电场的计算方法主要针对一条输电线路,采用的是二维计算模型,这种模型采用的是解析方法,可以求解二维空间内无限远处的电场强度。而交叉跨越区域电场强度的计算需要建立三维模型,针对三维空间的电场计算尚未有成熟的解析方法,较为常见的是利用数值方法。以有限元为原理的ansys仿真软件计算三维空间场强,但是必须已知求解区域和边界条件且细分网格以满足计算精度。为了解决这一问题,推导了两种无限长直导线三维空间电场强度计算公式,在确定求解区域和求解边界后,先利用公式计算三维截面上各点的场强值,然后将计算结果作为边界条件代入软件仿真。与交叉线路实地测量结果对比证明该方法可以应用于工程计算。并用这种方法计算了导线不同对地高度和不同相序情况下的电场分布,计算结果表明,提高导线对地高度和采用合理的相序排列可以有效地降低交叉线路线下电场强度。

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.