Impact of superficial and internal defects on electric field of composite insulators.

Abstract This paper presents measurements and calculations of electric field in samples with deliberately planted superficial and internal defects. Samples evaluated include full-scale composite insulators and cylindrical rods of the housing material. The goal of this work is to ascertain the viability of electric field as an indicator of impending failure of composite insulators that can develop such defects during manufacture and/or service. Measurements were performed with an Electro-optic probe based on Pockels effect. Calculations were performed using 3-dimensional Boundary Element Method package. Good agreement between the measurements and calculations has been demonstrated. The results show that conducting defects originating from the HV electrode produce a greater change in the electric field when compared to a healthy insulator than defects originating from the ground electrode or anywhere in between. The magnitude of the change in electric field when compared with a healthy sample diminished with increasing radial distance from the sample. Hence, it is important that the probe be placed close to the insulator shank for maximizing defect detection. [ABSTRACT FROM AUTHOR]