Rahmouni. Composite insulators solved problems of vandalism and coastal pollution.

Part 1 of this article appeared in the Nov-Dec 2000 Issue of INMR and focused on the increasing use of composite insulators on the distribution system of the Office National de l’Electricité (ONE).

The transmission system at ONE is comprised mainly of lines at 60 kV, 225 kV and 400 kV and is today still insulated predominantly with toughened glass. Nonetheless, over the past twenty years, a consistent yet cautious program has started which has seen the selective replacement of glass with composite insulators. In most instances, problems of vandalism or pollution have been the major motivating factors behind this changeover.

According to Ahmed Rahmouni, ONE’s Director of Transmission, the utility first began use of composite insulators back in 1983 when such units were installed on selected problematic portions of 225 kV and 60 kV lines running through the desert region south of the coastal city of Agadir. Says Rahmouni, “basically, since that experience we have been selectively replacing glass with composite insulators in those areas experiencing either pollution or vandalism.”

“The ONE’s philosophy with respect to composite insulators has been one of controlled risk, building confidence gradually by using them only in selective applications.”

Apparently, in 1992 lines in this area also began employing aerodynamic glass insulators designed to be self-cleaning under typical desert wind conditions. “However,” notes Abdelkebir Abarro, Manager of Studies and Analysis, “visual inspection of these glass chains revealed that in certain especially dusty areas there was still some accumulation of sand. This required that the glass insulator chains in affected portions of the line be washed at least once a year in order to prevent flashover problems whenever there were periods of fog.”

“Once we put in composite insulators in place of glass,” states Rahmouni, “both the pollution and the vandalism problems were basically solved.” In spite of this positive experience, however, he goes on to note that until very recently hardly any ONE transmission lines have been equipped solely with composite insulators. Rather, the utility’s philosophy has been one of controlled risk, building confidence gradually by using them only in selective applications.