3D electric field computation of a composite cross-arm

Abstract

Abstract-The use of composite insulators for overhead transmission lines has increased in the past decade. Various designs and models are now available for a wide range of voltages. The 3D Finite Element Analysis electric field distribution of such composite insulators has been of considerable interest due to its differences to 'conventional' glass or ceramic insulators. Results of such analysis are now widely available. The present paper presents and analyses the electric field distribution around a composite insulator, which is intended to replace both existing high voltage insulators and the cross-arms of transmission towers. The complex geometry of the composite cross-arm, which includes four separate insulator strings and different shed profiles across these members all connected to a common metallic nose cone, make it difficult to model in any 3D Finite Element Analysis package. The present paper will evaluate the electric fields on such a composite cross-arm, in regards to the areas of high field enhancement.

A coastal trial facility for high voltage composite cross-arms

“…The results from this facility combined with electrical FEA [5] will lead to improvements in understanding the performance of such cross-arms. In this case, the installation of reference cross-arms before the novel composite cross-arms are put in place will give valuable calibration information.…”

Electric field computation for a 400 kV composite cross-arm

“…The authors have previously presented the electric field analysis of the cross arm in [4]. The paper highlighted the use of FEA analysis in analyzing the electric field stress in view of satisfying the electric stress management criteria [4].…”

Electric Field and Potential Distribution in a 420 kV Novel Unibody Composite Cross-Arm

“…In general, the electrical field stresses on polymeric insulating materials such as silicone rubber shall be as low as possible to avoid tracking and erosion phenomena due to corona discharges. The following criteria are reported as evaluation factors in the design of composite cross-arms: 1) At 0.5 mm from insulation surface, maximum permissible electric field magnitudes to be less than 0.45 kV RMS /mm [11,8].…”

“…3) Maximum permissible electric field magnitude inside the core and sheds (Dielectric materials) to be less than 3 kV RMS /mm [11,8]. 4) Maximum permissible electric field magnitude at the triple junctions: 0.35 kV RMS /mm [8].…”

“…2) The local field on metal fittings to be below corona inception values 3 kV RMS /mm [11], maximum permissible electric field magnitude on metallic endfittings and electric field grading devices: 1.8 kV RMS /mm [8].…”