Transmission Tower Numerical Electric Field Models for Resilient System Design

Composite insulator use on overhead power lines is increasing internationally. Resilient system design should include using ac transmission tower numerical models to determine if electric fields on insulator housings and adjacent metal surfaces meet recommended thresholds. Insulator housing hydrophobicity is maintained if thresholds are met which provides system resilience if environmental pollution levels increase unexpected due to naturally occurring events. This paper discusses numerical modeling results of a proposed insulator housing electric field evaluation method used in a 400 kV RMS ac suspension tower model where the results correlated with water drop induced corona laboratory tests. The proposed method determines maximum average tangential electric fields over 10 mm along housing surfaces in the axial direction starting from the high voltage end fitting. The 400 kV RMS ac model sensitivity is discussed. Proposed and previously existing evaluation methods are then compared for a 220 kV RMS ac tension tower model.