A suspension insulator is a type of high resistivity insulator used in a variety of electrical networks suspended above ground level. A sturdy class of insulators, they are primarily used in systems operating at 33KV and above - a level that is beyond the voltage load capacity of many other insulators.

According to the type of connective join used, suspension insulators can be divided into two main types: cap-and-pin insulators (which uses a ball and socket or clevis-pin fastening) and the stronger interlink/Hewlett insulators (with two curved sections interlocking at a 90-degree angle).

As an insulator, suspension insulators are designed to constrict the flow of electricity to certain zones of an electrical circuit. Working alongside conductors (which assist electrical flow), this control of voltage distribution ensures that the circuit is working safely and to maximum efficiency.

Suspension insulators consist of a flexible metal rod housing a string of insulator discs. Each disc has a relatively low voltage capacity - allowing the stress of a high voltage load to be distributed throughout the series of discs and minimising the risk of overloading. This compartmentalised design of the insulator also ensures that if one disc becomes faulty, it does not compromise the integrity of the other insulator discs.

When installed the insulator is suspended at the end of a length of insulator string, which is attached to the pole or tower. The cross arms assist the insulator clamp in maintaining the correct position of the insulator.

The number of discs included on a suspension indicator varies according to the voltage load capacity required – the higher the voltage level, the greater the number of discs required. The discs are arranged in a line and linked together with metal to maximise their capacitive effect. Due to their design, each disc is capable of working either independently or collectively.

Suspension insulators are crafted from a variety of durable materials that can withstand even the most chaotic weather conditions, including porcelain/ceramic, glass, polymer, and composite (a mixture).

A suspension insulator is usually fitted vertically. However, in some circumstances (such as a dead-end or a sharp corner in a pole network), a higher level of stress is loaded onto the lines. In these situations, insulators are often fitted horizontally to provide supportive strength. Due to the change in their function, suspension insulators fitted in this way are known as strain insulators.

The installation of suspension insulators should always be carried out by experienced professionals using the necessary safety equipment.

Once these are in place, the basic steps of a suspension insulator installation are:

Site Preparation: Clearing the site of any debris and laying the insulator parts onto a protective covering;

• Insulator Assembly: The required number of discs are threaded onto the insulator rod and the necessary connecting hardware is attached;
• Hoisting Into Position: Using a pulley, the assembled insulator is then slowly lifted to the chosen spot;
• Mounting Insulator: The insulator is then aligned into position, with the cross arms and insulator clamp used to fix the insulator into place. End fittings and corona rings may also be attached to further secure the insulator.