Disc insulators

Disk insulators on a 225,000 volt line.

Detail glass insulators.

The disc insulators are a type of insulator used in transmission and distribution power lines. They are mainly made of glass and ceramic and their characteristics are standardized according to the weight or bearable force, level of admissible contamination and diameter.

The insulators together with the associated fittings have the mission of supporting the conductor of the line, to support it from the towers or poles that support it, providing at the same time the required electrical insulation.

Given a voltage level applied, a certain level of environmental contamination (according to the categories defined in Standard IEC 60815) and installation altitude with respect to sea level, it is required that the insulators as a whole have a certain minimum length to ensure that the line is adequately insulated to prevent grounding through the tower or pole structure. This is accomplished by grouping several of these insulators together in what is called an "isolator string".

• For transmission and distribution lines, standard 10-inch insulators are used.

• For Media Tension distribution lines, standard 6-inch insulators are used.

Given the appearance and continuous improvement of new polymeric materials, which have comparative advantages in terms of mechanical resistance against blows and better behavior in the face of contamination, this type of insulators has gradually fallen into disuse. In these types of applications, a string of disc insulators is now replaced by a single polymeric insulator, further simplifying installation or replacement.