INMR and its community of readers across the globe mourn the passing in May of Dr. Laurent Pargamin, former Scientific Director and a Senior Executive at Sediver in France. To those who remember him, he was among the key personalities behind that company’s pioneering work during the 1980s and 90s to develop a range of solid and hollow core composite insulators.

It could not have been easy for him back then to devote resources to a new technology that would compete head on with the toughened glass for which his company was most famous. Still, it seems he was motivated by what drives most great and restless minds – the perpetual quest for better solutions.

I first spoke to Laurent in 1989/1990 when, as a consultant, I interviewed him as part of a research study assessing new insulator technologies and market forces.

In 1993, when INMR (then known as INSULATOR NEWS & MARKET REPORT) was launched, Laurent supported the very first feature article about Sediver’s production of glass insulators at its former factory in Saint Yorre, France. Several years later, he was one of the prominent speakers at the 2nd INMR WORLD CONGRESS, held in Singapore.

Following are extracts from comments made 23 years ago by Dr. Pargamin as Key-Note Speaker at the 2003 INMR WORLD CONGRESS in Marbella, Spain.

Over an illustrious career spanning decades, he was involved in all facets of insulators. This makes his past observations and assessment on the historical and expected development of this technology still noteworthy today.

To Laurent’s family and friends, INMR extends our deepest condolences. He left an indelible mark on the industry he loved.

Marvin Zimmerman

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Comments by the Late Dr. Laurent Pargamin (2003)

“About 30 years ago, Hydro-Québec became probably the first major utility in the world to study and then specify composite insulators. The area of application was for a planned 1100 kV line which would run from a hydro-electric generating facility in northern Québec to load centres located a great distance away. The reason for this interest was primarily their lightweight which made them an excellent choice to replace heavy insulator strings along the very long route.

At about this same time, in several countries including the United States, vandalism involving gun shooting at ceramic insulators was creating a lot of difficulties on transmission lines. Composite insulators, with their slimmer profiles and rubber sheds were thought to be the ideal answer to this problem. It was also established early on that composite insulators offered better contamination performance compared to ceramic insulators.

Today, three decades later, the issue of weight still seems to dominate much decision-making in this field. According to a survey recently published by EPRI in the United States, the single major reason why American utilities select composite insulators is lower weight (42 per cent) while cost and resistance to vandalism (18 and 13 per cent respectively) are the next most important selection criteria. Resistance to contamination was offered as the principal reason by only 7 per cent of those responding.

These findings, incidentally, contrast with most of the rest of the world where contamination resistance has traditionally been and probably still is the main reason for the use of composite insulators.

In regard to materials and designs for these types of insulators, 25 years of research have led to improvements in both. Core rods have proven to be a critical part of composite insulators. Indeed, the problem of brittle fracture appeared right at the beginning of their development yet is only now starting to be fully understood and resolved.

At the same time, during the early 1970s the challenge was to find polymeric housing materials which could stand 30 to 50 years’ service in the harsh environments of many transmission lines. One of the first objectives in this regard was to define meaningful tests to evaluate these materials in the laboratory.

Service experience with some of the very early choices for housings, such as Teflon and cycloaliphatic epoxy, demonstrated that these materials were unable to offer a sufficiently long life. The material perhaps most widely used during the early development of composite insulators was EP rubber and this polymer provided reasonable properties at a low cost. Today, however, most designs of HV composite insulators involve silicone rubber.

What are the reasons for this remarkable breakthrough made by silicone?

First was the important contribution made by Tor Orbeck, a respected research engineer who worked for Dow Corning in the U.S. and issued numerous publications in this field. He demonstrated that the surface of silicone rubber had the ability to limit the leakage current on a wet insulator thus reducing the probability of flashover.

Subsequent work published in the 1980s by the former German insulator supplier, Ceramtec, proved that silicone rubber has the unique ability to encapsulate contamination on its surface by means of the migration of low molecular weight species from the bulk material. This phenomenon further reduces the risk of flashover as the potentially problematic contamination layer is rendered harmless.

Indeed, it was soon established that, under most operating conditions, silicone insulators offer superior performance as regards the probability of flashover. It should be noted, however, that ceramic and EP rubber insulators can also be used successfully in difficult environments if their leakage distance has been properly dimensioned.

Over the past two and a half decades, increasingly large quantities of composite insulators have been installed on transmission lines of 69 kV and above. The United States, with more than 4 million units now in service according to the EPRI survey, is the largest market however other countries with significant use include Canada, Australia, South Africa, China as well as many countries in South America and the Middle East.

Outside of the United States and Canada, the major driving force for the selection and application of these insulators has been their contamination performance and this helps to explain why silicone is the preferred housing material.

With the large and growing number of units in service, it is perhaps not too surprising that failures of composite insulators occurred. The EPRI survey has identified the main types of failure, as follows (in decreasing order of importance): brittle fracture linked with water ingress at the end fitting seal; tracking on the rod (referred to as flashunder) linked with a defective bond between rod and housing; mechanical failure due to defective crimping; and rods destroyed by discharge activity also linked to defective bonding internally.

The rate of defects is, however, very small: only 1 in some 65,000 units according to the EPRI survey. This incidence, while seemingly low, would nevertheless correspond to one line drop per 655,000 units and this is still greater than for ceramic cap and pin type insulators. Such a level of failures is therefore cause for concern among utilities which use large numbers of composite insulators. This is all the more the case when it comes to live line work. How is it possible to consistently recognize a deteriorated composite insulator?

Here are some thoughts on the need for additional research and product development which should help to reassure users of composite insulators:

• Improve reliability by developing better end fitting to housing seals, since this interface is responsible for a large proportion of all failures. It is indeed a challenge to have seals which can perform for 30 to 50 years in such an environment.

• Find better ways to inspect and assess the condition of insulators in service. Users should be able to detect the starting point of all four of the principal defects mentioned earlier. This issue is especially important for live line work. Glass insulators still have a significant advantage when it comes to ease of inspection and safety during live line work.

• Improve manufacturing processes and, in particular, the various quality control tests which are conducted during manufacturing.

Today, well-manufactured composite insulators with good housing-to-metal fitting seals have proven that they are able to withstand the stresses of service for more than 25 years. However, uncertainties regarding reliability and inspection have limited their penetration to less than 30 per cent worldwide (probably 80 per cent in the US). To increase this share in the future, all the above concerns will have to be addressed.”