A Historical Glimpse of Electrical Insulators

Electrical insulators are very important parts of sub-stations and distribution and transmission lines within the electric power system. In the early days, insulators were made of ceramic and glass materials. In 1963, the first non-ceramic materials were used for insulation and the very first polymer insulators were developed to improve performance where ceramics did not perform well.


A polymeric insulator consists of a fiberglass core rod covered by rubber housing and weather-sheds of polymer such as silicone rubber, polytetrafluoroethylene, EPDM (ethylene propylene diene monomer) and equipped with metal end fittings. Polymers, sometimes called composite insulators, are made of at least two insulating parts — a core and housing equipped with end fittings.

In the late 1970 and early 1980 generations, polymer insulators were used primarily as special designs for extreme applications at a premium cost to the utilities. Polymeric insulators have many advantages over ceramic and glass insulators:  good performance in contaminated environments, lightweight, vandal resistant, easy to handle, and maintenance free. Because of these properties, they gained popularity worldwide and sparked a series of manufacturing and design improvements that led to the polymer insulators of today.  Polymer transitioned from a premium high cost insulator to today’s lower cost insulator when compared to porcelain or glass.

MPS Insulators
The MacLean Power Polymer (Reliable) insulator dates back to 1978, when the modular insulator process was first licensed from a German company, Rosenthal.  By 1982, MPS-Reliable was manufacturing insulators in the United States and broke free from the license agreement. In 1984, the MPS silicone formulation was introduced when the Rosenthal “Blue” silicone was changed to the Reliable grey color. This silicone is the longest unchanged formulation in the industry today, is field proven and laboratory tested, and remains the backbone of the MPS insulator product line.

Through the years, MPS has led the industry in technological advances, application improvements, and manufacturing enhancements (Smart Fit Corona Rings, PST Seal, CR E-Glass, and Stacked Sheds). There are still 1984 First Generation MPS insulators in service today, 30 years and still going strong. The advanced features and benefits of the APEX Generation insulator along with MPS Application Support promises even longer-term performance.

1984-2014     table