Why should I choose HDPE over porcelain for my insulators?
By Steve Lindsay
Utility professionals are accustomed to using porcelain insulators. And for good reason. Porcelain has helped to build the backbone of the existing electrical grid and in the right conditions can last up to 50 years in the field. Porcelain insulators, whether at low, medium or high voltage levels, are a very cost effective solution for a utility. But porcelain insulators come with a few drawbacks as well.
Porcelain is a very fragile material that is prone to damage. Porcelain can get damaged during shipping from the manufacturer, transportation to the work site, during installation and even once it is placed in service. Vandalism is, and will remain, an issue for utilities across the country. Weather conditions can also play a major role in the failure of porcelain insulators. Lightning strikes, falling branches, heavy condensation and extreme weather swings can all contribute to reducing the life span of a porcelain insulator. In cold weather climates, one of the major problems is the “freeze-thaw” cycle. Any microfracture or manufacturing defect can lead to the ingress of water during the “thaw” cycle and then that area will freeze as temperatures drop. This leads to expansion of the defect which in turn leads to breakage of the insulator. This will invariably lead to a failure and an outage.
HDPE, or high density polyethylene, is an excellent material as a direct replacement for distribution insulators of all types. HDPE is much lighter than its porcelain counterparts and almost impervious to the cracking so common to porcelain. Because it is impact resistant, HDPE will survive transportation to the work site as well as be much less likely to fail from common vandalism like a BB shot. HDPE is also compatible with both insulated and bare conductors used by so many utilities.
HDPE is an excellent choice for utilities that are in regions that are prone to extreme cold weather as well as areas that are prone to “freeze-thaw” cycles. The lack of cracking in HDPE insulators makes it the perfect choice for these utilities. HDPE also has another advantage over porcelain – a higher leakage distance. With more leakage distance, this also makes HDPE an improvement over porcelain in coastal regions, areas with high humidity and condensation as well as areas that are susceptible to heavy pollutants. The inherent hydrophobicity in HDPE acts as “self cleaning” mechanism.
With over 50 years of field experience, it is clear why many utilities have made or are considering the switch from porcelain to HDPE.