Online leakage current monitoring of 400 kV insulator strings in polluted areas

The author comments on the paper by J.L. Fierro-chavez et al. (see ibid., vol.143, no.6, p.560-4, 1996) in which the authors propose a system as a diagnostic tool for the measurement of leakage current and surface resistance of insulators. This system may help to diagnose problems in insulators and take preventive action when needed. The purpose of this comment is to shed light on another important aspect of this paper, namely the hydrophobicity of the silicone-based RTV-coated insulators which was not discussed by Fierro-chavez et al