Disconnectors are devices that open and close a circuit in medium and high voltage systems while it is off-load. They come in indoor and outdoor versions and fall into four categories: plain, earthed, fused and fused-earthed.
They are manufactured as three-pole units operated by a common mechanism for all poles, suitable for mounting on a wall or vertical plane. On request they can also be produced as single-pole units for mounting on a vertical or horizontal plane. Disconnectors may be operated under voltage; they must never be opened or closed under load.
Outdoor medium voltage disconnectors provide isolation between a high voltage line and a low voltage line in power systems and prevent damage caused by overvoltage. They are formed from three independent main components: the disconnector blades provide isolation between the lines and allow them to be opened and closed, the earthing switch protects the system by momentarily earthing the high voltage line, and the operating mechanism controls the movement of the blades.
Outdoor disconnectors are used on distribution lines, transformers, circuit breakers, capacitor banks and power transformers. Because they play a safety-critical role, their installation, maintenance and operation must be carried out only by trained and experienced personnel.
Load break switches differ from disconnectors in that they can open and close a medium voltage circuit while it is on load. The arc chute fitted to the device suppresses the arc formed during switching, which is what allows operation under load. They are also divided into plain, earthed, fused and fused-earthed categories, and can be supplied with porcelain, epoxy or silicone insulators as preferred.
Insulators fall into two groups: porcelain and silicone. Silicone insulators are increasingly preferred as an alternative to porcelain for their flexibility, light weight, UV resistance and hydrophobic properties. A high-strength glass fibre core between two metal end fittings provides both mechanical strength and insulation, while the outer housing uses a polymeric composite material.
Disconnectors are manufactured to TS EN 62271-102 under ISO 9001 assurance.
