Discussing with staff from Kenitra regional office a section of 220 kV transmission line now equipped with composite insulators due to former heavy incidence of vandalism.

In 1986, anticipating good performance of composite insulators under pollution, ONE embarked on a pilot installation of such insulators in a region with very high levels of dust and marine contamination. The favourable experience obtained with these EPDM insulators gave the utility confidence in this new product. Indeed, after almost 15 years, these insulators are apparently still providing trouble-free service. Shortly after the installation of these first composite insulators, the utility decided to utilize them to combat vandalism as well.

For ONE, the move to composite insulators has been made with caution. Working with the manufacturer, the utility installed them only gradually in sections of lines where pollution was severe and where vandalism was a problem. These insulators were then inspected regularly to monitor their conidtion and performance. This process led to an increased confidence in these insulators and, at the same time, allowed ONE personnel to gradually develop the expertise required to work with them in the future.

By 1991, about 10,000 composite insulator units were already in service in Morocco. Their satisfactory performance encouraged ONE to subsequently require their use in all regions affected by vandalism.

Composite insulators have basically eliminated the vandalism problem and performed well under the severe pollution conditions found in the many parts of the country. Based on this, ONE has now taken the final step in the process, namely using them on all of their new lines. In addition, those sections of existing lines which are most afflicted by vandalism or where conventional insulators cannot cope with the severe levels of pollution, will now be re-equipped with composite insulators.

ONE’s gradual move toward composite insulators has allowed the utility, through regular inspections and careful evaluation programs, to become increasingly familiar with their special characteristics and requirements. As a result, they are now well-accepted by the utility personnel. Indeed, this careful, step-by-step approach seems to have served the utility remarkably well.

However, it should be pointed out that if such a progressive evaluation process is being performed on only one specific insulator type, then the acquired experience applies only to that particular design. In this respect, as ONE adopts more general use of composite insulators, management should be aware that the knowledge gained may not necessarily be directly transferable to all types of composite insulators.

Indeed, one special aspect of composite insulators is that their performance is a function of many parameters. Shed material and design, especially near the end fittings, as well as the various manufacturing processes are among such critical variables. Each new insulator design and type must therefore be evaluated with caution and this is often a laborious task. Nonetheless, utilities must ensure that their engineers and linesmen are familiar with the possible types of damage associated with ageing and the possible failure modes particular to each design of composite insulator.