Disconnectors and earth switches for HV and EHV substations.

Two rotating post insulators per phase, each carrying half of the blade, meeting at a single contact in the centre. Rated up to 4,000 A as standard, with 6,000 and 8,000 A built to order at 362 to 550 kV. The most compact choice for phase spacing at transmission voltages, and the standard arrangement from 245 kV upwards.

A centre rotating insulator turns a single blade that opens at both ends, giving two isolating gaps in series. Rated up to 3,150 A, available with direct contact or twisted blade contact, and for upright, underhung or vertical mounting.

Mounted on the disconnector base on the line or busbar side and mechanically interlocked with the main blades. From 120 kV the earthing blade twists 90 degrees into its contact as it closes, reducing friction and operating force. Short time ratings match the disconnector.

Every type is available in two versions. Standard models have silver plated contacts, with routine maintenance every three years. Severe Duty models use self lubricating silver graphite contacts and stainless steel ball bearings throughout, with no grease to dry out or harden, extending routine maintenance to every six years, against two to three years for the market standard.

Enclosed motor mechanisms for local and remote operation, including a sealed type rated for 12 years without maintenance, and manual mechanisms with a removable handle for disconnectors and earthing switches below 300 kV.

Disconnectors can be designed to replace units from other manufacturers on existing structures and foundations, with terminal adapters to match existing connections.

Severe Duty models need routine maintenance only every six years, against two to three years for the market standard, cutting outages, site visits and lifetime cost. Self lubricating silver graphite contacts need no grease and keep wear and operating force low, and stainless steel ball bearings keep operation smooth after long periods without switching.

Many of these disconnectors installed in New Zealand and Australian substations decades ago are still in service after more than 50 years, a track record few disconnectors in the world can match.

On centre break disconnectors, current passes through each hinge on a flexible laminated copper conductor, not a sliding contact, so there is no joint to wear, oxidise or heat up. Contact fingers share the current evenly, and double contact pressure wipes the contacts clean every time the switch closes.

From 120 kV, a hook device locks the contacts together so earthquakes, strong wind and short circuit forces cannot push them apart. A dead point in the base mechanism stops the blades being forced open, and above 170 kV a guide steers the contact into place on every close.

Every model is designed to the IEEE 693 and IEC 62271-207 High seismic levels and shake table tested in three axes. Every type operates in typhoon winds of 40 m/s, tested to 60 m/s, and through high humidity, salt laden air, heavy snow and extreme heat and cold.

A built in motor and reduction gear drive the operating shaft, with no exposed gears to grease and an electric brake that stops the blades cleanly without rebound. Electrical components sit on a single panel for easy replacement, and a sealed version runs 12 years without maintenance.

Our disconnectors and earthing switches are type tested to both IEC and ANSI standards, IEC 62271-102 and IEC 62271-1, and IEEE C37.30.1 and ANSI C37.34, at an internationally accredited laboratory in Europe. They carried 63 kA for 3 seconds without contact welding, withstood lightning impulse voltages above the ANSI requirement, and completed 10,000 operations without maintenance.