Load break switches are fundamental to the reliable operation of the distribution grid, but not all designs are evenly matched.
Among some of the earliest equipment developed for the distribution network, load break switches (LBS) are an essential element to the reliable operation of the distribution grid.
They enable operators to switch elements of the network on and off as required and allow operators to divide the overhead distribution network into smaller zones, minimising the number of people effected by network faults.
This ability to divide the network will be critical as Australia’s continues its clean energy transition and the grid adapts to increasing input from renewable sources, as resources such as wind and solar can cause fluctuations in electricity supply and distribution.
The evolution of LBS
Since their invention, there have been multiple LBS designs used.
Air break switches rely on the distance between contacts in an open-air environment to provide isolation, however, exposure to the weather means they are prone to corrosion and device failure. Additionally, the exposed insulation gap can pose significant risk to operators when the switch is in the open position.
To combat this, the SF6 LBS was developed, encasing the contacts of the switch in a sealed metal tank filled with sulphur hexafluoride (SF6). Though this design is more reliable, the visible isolation is removed, meaning operators must rely on the gas and external indicators to confirm the insulation. However, SF6 has since been identified as one of the world’s most potent greenhouse gases.
Modern LBS design utilises dielectric insulation to enclose the switch, which protects the contacts of the switch, improves the device’s reliability and eliminates the use of harmful gas. However, the major flaw with this design is a lack of visible isolation.
Without clear visibility, it is difficult for operators to confirm that the current has been isolated, which poses a significant safety risk.
A modern solution
NOJA Power’s VISI-SWITCH® is the world’s first solid dielectric enclosed LBS with visible isolation.
This means that operators can count on the reliability of a dielectric LBS with the safety benefits of visible isolation, enabling them to visually confirm the point of isolation before undertaking any linework.
The SF6-free design uses a vacuum interrupter and an air-insulated isolator, with the vacuum interrupter providing the current make and break capability and the isolator providing the working point of isolation, with zero worry of harm to the environment.
When an operator opens a NOJA Power VISI-SWITCH®, the sequencing mechanism first opens the vacuum interrupter to break the line current, then automatically retracts the isolator.
To close the VISI-SWITCH®, the order of operations is reversed – the mechanism closes the isolator while there is no current present, and the vacuum interrupter is closed to restore the circuit.
Because it is enclosed, the isolator remains reliable, safe and free from corrosion, meaning it is maintenance free for its entire 30-year service life.
Manufactured at its Brisbane headquarters, NOJA Power has ramped up production and released a new user manual with the addition of operational accessories to help operators with installation and integration.
As Australia continues its renewable energy transition, the VISI-SWITCH offers a reliable, safe and sustainable LBS to support the grid through the inevitable changes in energy generation and distribution.
For more information, visit nojapower.com.au
