Composite Hollow Insulators

Composite hollow insulators are used in outdoor AC electrical equipment or indoor with rated voltages between 1 kV and 800 kV and frequencies to 100 Hz, or in DC equipment with rated voltage above 1.5 kV.  They usually serve as enclosures (covers) for current transformers and power transformers, circuit breakers, bushings, etc. and surge arresters or other electrical equipment.

Because of excellent mechanical properties, flexibility, relatively low weight compared to ceramic covers and excellent electrical parameters, composite hollow insulators are preferred
for use in overhead installations (pollution degree zones I – IV), especially in seismic hazard areas.

In addition, composite tubular insulators are characterized by:

• High resistance to weathering, including UV radiation,
• Excellent hydrophobicity and chemical resistance of silicone elastomers.

Composite hollow insulators (insulating covers) are made of glass-epoxy tube, metal fittings fixed at the end of the tube and insulating sheath made of silicone rubber. The tube is made of
made of ECR glass fibre saturated with epoxy composition. It is the insulator's supporting core
and is used to transfer mechanical loads (mainly bending loads and stress, sometimes also torsional loads). Metal end fittings are fixed to the tube ends with epoxy adhesive of of high mechanical and thermal strength. The silicone cover is moulded by LSR liquid silicone elastomer injection, which protects the core against the environment
and at the same time, by appropriate shaping of the sheds, determines the electrical properties of the insulator.