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Product overview

Overview of our long rod insulators

Thanks to their superior design and low weight, 3FL long rod insulators are especially suitable for overhead compact-line applications. They are also more economical to transport and install, and make it possible to build more space-saving electricity poles.

Siemens Long Rod Insulator 3FL

Design of 3FL long rod insulators


The 3FL insulator housing is a one-piece HTV1 silicone rubber housing made in a one-shot injection molding process. The HTV silicone is directly molded onto the FRP2 rod by overlapping the triple junction point and part of the metal end fittings.

The core rod is a boron-free, corrosion- resistant ECR3 fiberglass-reinforced plastic rod (FRP rod). Due to the extremely high hydrolysis and acid resistance of the FRP rod the risk of so-called brittle fracture is completely eliminated for 3FL insulators. The triple junction point in the connection zone (FRP rod/end fitting/silicone) is inside the silicone housing and completely sealed, making an additional sealing system unnecessary here.

The special design of the end fitting and the form of the silicone on the 3FL reduce the local increase of the electrical field strength inside the junction zone to a minimum. This effectively prevents corrosion and eliminates the risk of subsequent failure.

The end fittings are made of steel or cast steel and galvanized. The 3FL is available with all standard end fittings up to 210 kN. The 3FL is 100% interchangeable and compatible with existing insulators of all types.


Silicone rubber housing for best pollution layer performance

The excellent corrosion resistance of the HTV silicone rubber guarantees a long service life and maximum reliability for the 3FL, even in the most extreme weather conditions. The silicone material used on Siemens insulators is extremely hydrophobic, keeping water and pollution layers from forming any lasting conductive film. Surface currents and the risk of insulator flashovers are reduced to a minimum, especially in regions impacted by air pollution or salt spray.

1HTV: high-temperature vulcanizing
2FRP: fiberglass-reinforced plastic
3ECR glass: electrical and corrosion-resistant glass

Types of models


3FL3 and 3FL4 for high-voltage networks up to 550 kV

3FL3 and 3FL4 insulators are available in an SML class of 100 and 120 kN.

Technical data


1 Rated lightning impulse withstand voltage according to 60071-1
2 Rated switching impulse withstand voltage is not applicable for system voltages with Um < 300 kV
Rated short duration power frequency withstand voltage level is not applicable for system voltages with Um > 245kV


3FL5 and 3FL6 for high-voltage networks up to 550 kV

3FL5 and 3FL6 insulators are available in an SML class of 160 and 210 kN.

Technical data