Corona resistance of low density polyethylene

Abstract

Polyethylene is a commonly used electrical insulating material in both terrestrial and aerospace equipment. In high voltage applications, it can be exposed to very high electrical field stress, resulting in long term exposure to low-level corona at stresses much below dielectric breakdown threshold. The surface degradation of low density polyethylene insulators under high electrical stress has been investigated using several surface techniques in conjunction with discharge current measurements. Degradation studies have been conducted in air with a relative humidity of 50%. Electrical diagnostics have included discharge measurements with both pulse (partial discharge) and direct current (dc) components. Changes in the surface morphology have been characterized by surface analysis techniques, which include X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) roughness measurements. Antioxidant performance for thermal stabilization of thermoplastics is well established through tests such as Oxidative Induction Time tests. The utility of antioxidants for retardation of electrical degradation is also investigated. Proposed chemical mechanisms for electric field induced degradation are similar to chemical mechanisms for thermally induced degradation. The performance of antioxidants as high electrical stress stabilizers will be reported, as measured by XPS.