Deterioration of polymeric insulators using exclusive agents

Abstract

Nowadays, glass and porcelain insulators are being systematically changed by polymeric insulators, because of its advantages, as easy installation, reduced weight, low cost in the construction and transportation, and resistance to the vandalism. However polymeric insulators have disadvantages, as the difficulty about visual damage detection. Power outages due to polymeric insulators failures cause billions of dollars of product damage each year and, in most cases, a simple inspection of the ground is not enough to visualize the defects in operation insulators before the outage. As these equipments longevity is reduced according to eventual internal defects and hostile ambient conditions, it is necessary to develop and improve monitoring techniques. Infield, the polymer suffers a multi-stress aging, due to the many deterioration agents that are present. The result is a combination of effects that, in long term, turn the insulators inappropriate to use in electric system. These effects, however, mask each other, and it is hard to tell which agent is causing which effect, and how to detect it. This knowledge is very useful when the energy company has polymeric insulators in facilities under different climate conditions, as happens in Brazilian Northeast. This paper brings some results of deterioration tests made in laboratory, with new (perfect) insulators taken from the warehouse. Initially perfect insulators have passed by a visual inspection and tested with some diagnostic techniques as thermograph, corona detection, and partial discharges inspection, Fourier Transformed Infra-red Spectroscopy (FTIR), Thermal Analyses Techniques as Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analyses (TGA), Scanning Electronic Microscopy (MEV) and Mechanical tests. Then, these insulators were exposed to different aging agents or aging agents groups, exclusively, in order to evaluate the effects of each agent or group of agents, in an isolated way. The aging methods used were dry high voltage application, salty fog and high voltage application, Weather-ometer, Thermal Aging and Water in high temperature. (4 pages)