Development of Electric-Field Stress Control Devices for a 132 kV Insulating Cross-Arm Using Finite-Element Analysis

摘要

Insulating cross-arms (ICA) allow compaction or upgrading of transmission lines. The process of designing and verifying the performance of electric field grading devices is reported for rigid cross-arms on a 132 kV lattice tower. For the grounded end, traditional grading devices resembling rings which follow the general shape of the insulators were designed. For the high-voltage (HV) end, an iterative process yielded a novel grading device which is a unibody piece of cast aluminium that manages the field on all four ICA members. Finite element analysis (FEA) simulations show that the electric field magnitude at the triple junctions of the insulating members meet the design criteria of 3.5 kV/cm. Also the field magnitude on the metallic end-fittings and electric field grading devices is maintained below 18 kV/cm. The corona extinction test was performed on ICA assemblies showing that the grading devices can effectively control the electric field at voltages of up to 132 kV since the average corona extinction voltage was 173.7 kV, well above the required value. The complete ICA assemblies were installed on an existing line in Scotland in August 2013. This paper provides a set of recommendations for use of FEA in the design of complex insulation geometries.