Increased protection with plastic and Silicone

In 2007, the first hollow composite insulators left the production floor of Maschinenfabrik Reinhausen (MR) under the brand name ReCoTec® (Reinhausen Composite Technology). Since then, Recotec® insulators have been taking over the market.

The hollow composite insulator in the lobby of the plant in Haslbach is No. 001 of the production batch for the first-ever delivery of ReCoTec® insulators, which left the plant on 9 May 2007. (© Reinhausen Power Composites)

The earth quakes. Seismometers show a 6 on the Richter scale and the primary substation experiences some very powerful shaking. Yet everything is fine. All the bushings and insulators make it through the intense quaking unscathed and power can continue to flow. This is the result every grid operator hopes for in this kind of extreme situation.

Outdoors, however, insulators are also exposed to many other stresses. They collect a remarkable amount of contamination particularly in industrial regions, near refineries, in regions with surface coal mining or in congested areas with severe particulate matter pollution. On the seashore, salt build-up interferes with the insulating capability. There are also mechanical stresses in many environments due to operation and the local weather conditions.


Ceramic insulators have a long tradition in such applications. However, they have been left behind in recent years in favor of hollow composite insulators. These insulators are more lightweight and easier to handle. Porcelain insulators burst during an earthquake or when vandalized, damaging surrounding equipment in the process and, in some situations, even posing a risk to people.

Each individual fin of the silicone shielding is checked prior to delivery. (© Armin Weigel)

This is why Hochspannungsgeräte GmbH (HSP) in Troisdorf, Germany near Cologne has been relying on hollow composite insulators for many years. The leading global manufacturer of high-voltage bushings for transformers, wall bushings and gas-insulated switchgear (GIS) was the first customer for which Maschinenfabrik Reinhausen (MR) produced ReCoTec® insulators in 2007. Their special feature: Instead of being made of porcelain, these insulators are composed of glass-fiber-reinforced plastic with silicone shielding

MR already had a great deal of experience with insulating materials. “For over 30 years, we’ve produced insulating tubes with complex electrical requirements for use on our tap changers ourselves. This is where the idea came from to get into the business of hollow composite insulators,” says Dr. Bernd Kempa, Managing Director of Reinhausen Power Composites GmbH.


ReCoTec® insulators have rigorous requirements regarding mechanical loads, seal-tightness and dielectric strength. The properties of the composite materials are crucial for the quality and reliability of the products, and perfect command of the production process is therefore necessary.

ReCoTec® insulators consist of an insulating tube made of glass fiber-reinforced plastic (GFRP), aluminum fittings and a silicone shielding. They are designed perfectly for the respective application in accordance with specific customer requirements. The laminate structure of the GFRP tube is essential for the mechanical and electrical properties.


Owing to the many advantageous properties of the innovative materials, demand has grown steadily for ReCoTec® hollow composite insulators and other products under the Rotafil® brand name. This is why MR founded Reinhausen Power Composites GmbH (RPC) back in 2009. Through all the years, RPC and the first customer of hollow composite insulators have remained close. Last year, the 10,000th insulator was sent to HSP in Troisdorf.

“When we started production of ReCoTec® ten years ago, insulators made of porcelain were still the standard. Today, hollow composite insulators are taking over more and more of the market.” Dr. Bernd Kempa, Managing Director of RPC

Dr. Kempa is confident that the market for hollow composite insulators will continue to grow, “Energy consumption will steadily increase around the world. In China and India, for example, there are many new high-voltage direct current (HVDC) transmission networks for voltages up to 1100 kV DC. It would scarcely be possible to implement applications at these voltage levels using porcelain.”


Hollow composite insulators Porcelain insulators
Silicone is hydrophobic, meaning that it repels water; contamination rolls off easily due to this effect. Porcelain is not hydrophobic and must therefore be cleaned frequently.
Smaller wall thicknesses are possible due to the high strength of the glass-fiber-reinforced plastic. This makes the insulator lighter. Porcelain insulators require thicker walls and have a higher specific weight. They are therefore up to 40 percent heavier.
Hollow composite insulators are flexible and therefore markedly more resilient in the event of an earthquake. Porcelain insulators have a risk of breaking during an earthquake.
In the event of an outage or external damage, hollow composite insulators are explosion-proof and do not fracture. If damaged, sharp-edged porcelain pieces can be thrown through the air and cause additional damage.
The production and delivery time is substantially shorter than for porcelain insulators. With porcelain insulators, it may be months before delivery, and just firing the porcelain requires weeks.

Further information:

Learn more about ReCoTec® hollow composite insulators here

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