Electric field calculation and grading ring design for 330kV terminal tower with composite cross-arms

In order to analyze the potential and electric field distribution of one 330kV AC terminal tower with composite cross-arms, the full three-dimensional (3D) finite-element method (FEM) model was established for numerical simulation, using software ANSYS. The influences of tower, earth, wires and inter-phase interaction were considered. The distributions of potential and electric field on the cross-arms, insulators and fittings were calculated with FEM harmonic analysis. Based on the calculation results in the original design, a grading ring configuration scheme of the composite cross-arms and insulators was proposed. And the structure parameters of grading rings were optimized. The calculation results show that in the original design, the maximum E-field strength on the silicone rubber (SIR) housings is 1156V/mm, and that on the rings is 3112V/mm. While in the optimized design, the maximum E-field strengths on the SIR housings and rings are 389V/mm and 2279V/mm respectively. It could be inferred that after optimization, the voltage-sharing performance of composite cross-arms and insulators has been improved, and the E-field strength of each key location on the terminal tower was proved to be lower than the critical value.