Page 43 - Energize April 2021

TECHNICAL

The CI can provide tensile, bending and compressive strength, Vertical mounting (suspension insulators)
and this property allows the CI to be substituted for the metal Composite insulators may be mounted vertically as a
structural components of a conventional OHL. suspension insulator, either individually fixed rigidly to the metal
cross arm, or in combination as a V suspension structure, as
Unlike conventional insulator strings, the composite insulator has shown in Figure 4.
a solid core and a rigid structure. This allows for either horizontal
or vertical mounting. The components of the insulator are: Horizontal mounted insulators (post mount)
• Core rod: The core is the internal insulating part of a The post mount configuration gives the greatest size reduction
composite insulator. It carries the mechanical load which potential for composite insulators. Post mount involves mounting
may be tensile or flexural. It consists mainly of glass fibres single insulators or combinations of insulators horizontally on the
within a resin matrix to achieve maximum tensile strength. side of the support structure.
• Housing: The silicone rubber housing provides electrical Line post insulators are fixed directly to the support mast by
insulation and protects the core from the elements and means of a mounting structure.
is moulded onto the core. It may be equipped with
weathersheds. Combination mounting: braced twin post or horizontal design
• Weathersheds: These are insulating parts, projecting from Composite insulators may be combined in braced line post
the housing or sheath, intended to increase the leakage configuration, which consists of a combination of a line post and
distance and to provide an interrupted path for water suspension insulator. This increases the vertical load capacity of the
drainage. line post assembly.
• End fittings: End fittings transmit the mechanical load to the
core. They are usually made from forged steel, malleable cast Insulated cross-arm
iron or aluminium. Unlike a braced line post or a horizontal V, which are two-
dimensional structures, an insulated cross-arm is made up of a
Composite insulators are much lighter than glass or porcelain minimum of three insulators disposed in a triangulated position to
insulators, and the rigid structure allows them to function as
structural members of cross arms. The composite insulator may
be used in a vertical or horizontal configuration. Configurations
include single insulators or combinations of insulators used to
construct the required support structure.

Figure 4: V suspension structure using composite insulators (Pfisterer)

Figure 3: Composite suspension insulator (Pfisterer) Figure 5: Line post insulator (Sediver ) 6

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