Comparison of zeroth-order and harmonic expansion calculation of the electrostatic parameters of three-conductor bundles

An electrostatic field analysis of three-conductor bundles in triangular and flat (coplanar) configurations above ground is presented. The two configurations are compared from the viewpoint of bundle-to-ground capacitance, geometric mean radius, surface charge distributions, and electric field strength. Approximate results, neglecting proximity effects are firstly obtained considering a zeroth-order approach for the potential coefficient matrix. Accurate results are determined by application of the harmonic expansion method in order to correctly deal with proximity effects between individual conductors of the bundle. The latter approach yields significantly increased values for the electric field strength at certain points along the circumference of the individual conductors of the bundle. It is shown that the triangular configuration is more effective as far as corona problems are concerned.