As first reported in an article published by INMR in May/June 1997 (Vol. 5 No. 3), more and more utilities throughout the world are being confronted with the task of replacing ageing cap and pin type station post insulators. One such utility in Canada has used this situation as the basis for conducting special tests designed to determine whether hollow core non-ceramic insulators could represent a feasible option to more
conventional porcelain solid core station posts in this replacement application.
The basic rationale at Ontario Hydro for considering selection of hollow composite insulators was cost-savings associated with quicker construction and less service interruption time. According to Anne-Marie Sahazizian, Manager of Station Design & Technical Services for Network Services, “outages associated with retrofit construction projects tend to be very expensive. Therefore, anything that our staff can do to speed up this work has a definite economic payback. Generally-speaking, composite support insulators are superior from the ergonomic point of view since they are light and easier to install without the need for hoists or cranes.”
However, one of the basic concerns has been how these types of insulators respond in terms of dynamic mechanical strength to the high forces present during short circuit currents of up to 80 kA. For this reason, Ontario Hydro Technologies - the research and testing arm of the giant utility - was asked to develop and conduct investigations into this matter. John Kuffel, Manager of the Electrical Testing
Laboratories at Ontario Hydro Technologies indicates that initial testing was undertaken at 230
kV simply because this was the voltage of the original needs brought forward by Network Services. 
However, researchers also developed a mathematical model so as to allow the findings of the test to apply across a range of different substation requirements.
Speaking at the SYMPOSIUM ON MODERN INSULATOR TECHNOLOGIES held last November in Florida, Kuffel announced that the short-circuit performance of hollow-core composite insulators was found to be very satisfactory.
He reported “in spite of a shock load of approximately 1.3 times the static damage limit of the insulators tested, no damage was detected even using sensitive acoustic emission. This result is consistent with the ability of composite materials to withstand higher shock loads than static loads.”
