Electric stress computations for designing a novel unibody composite cross-arm using finite element method

This paper deal with the electrical performance of a newly proposed fully composite pylon in Denmark, which has a unibody composite cross-arm at 420 kV highest system voltage level. Electric field consideration along the insulations of the novel unibody cross-arm is one of the most important requirements in the design process of a non-traditional pylon. In this paper, ANSYS finite element software is used to calculate the electric field and potential distribution around and inside the fully composite pylon. Electric field criteria related to the design of composite cross-arms are reviewed and applied for interpreting the electrical performance of the unibody cross-arm at power frequency stresses. Three different designs of non-conductive conductor clamp are assumed for the attachment points between phase conductors and the unibody cross-arm. The side effects of conductor clamp are included in 2D modeling in order to determine the minimum required height for phase conductors at the top of the unibody cross-arm. Considering the side effects of phase conductors at both sides of conductor clamp, the application of steel enclosures with an appropriate diameter is introduced to be used around the phase conductors in order to reduce the electric field magnitudes in the region of the conductor clamp. Finally, the feasibility of utilizing steel enclosures for modifying electric stresses inside the conductor clamp and unibody cross-arm is investigated by a 3D finite element analysis.