Three Techniques for Connecting Surge Arrestors to Reclosers

Surge arrestors are essential protection devices for overhead switchgear. These assets mitigate the impact of switching surges and lightning strikes, improving network reliability and protecting assets such as Reclosers or Transformers.

Some Reclosers, such as the NOJA Power OSM® Recloser device, can have surge arrestors earthed through the switchgear tank. This is achieved through a masked off paint free connection in the stainless steel, affording an effective current path to earth. This leaves the connection point on the high voltage side to be addressed.

When it comes to connecting surge arrestors to overhead switchgear, there are multiple techniques employed.

The primary engineering objective is to connect the surge arrestor as close as possible to the asset under protection, and for the earth path to be effective and maintained.

In this article, we share three design topologies for connecting Surge

Midline connection

Among the most applied techniques for Surge Arrestor Connection is the midline lug connection method. In this connection method, a short lead is connected from the top of the surge arrestor to the mainline with a lug.

This installation method allows for rapid replacement of legacy equipment, where old asset terminals are reused and connected to the new switchgear.

Surge arrestor terminations are made to the same lug. Once installed, the bare conductor is sealed with heat shrink, providing mitigation for wildlife incursion.

Figure 1 shows a typical midline lug connection method, complete with insulation over the surge arrestor and lug connection.

Palm Connector Method

Another common method of surge arrestor connection is through use of a Palm connector as the recloser terminal.

In this connection method, the surge arrestor lead is terminated with a lug connector, which can be bolted directly to the recloser palm terminal. While this terminal is slightly more expensive than a tunnel connector, this installation technique allows for uninterrupted insulation on the HV leads between the overhead lines and the switchgear terminals, minimizing site works and risk of wildlife incursion.

Surge Arrestor Bar Method

As an alternative, the surge arrestor lead can be replaced entirely by busbar. This installation technique provides the shortest distance from surge arrestor terminal to recloser terminal, and allows the entire connection to be covered by a single animal guard.

This installation requires standardisation of surge arrestor type, as the buswork design constrains the possible height of the surge arrestor.

However, if this is standardised, the surge arrestor bar method provides the neatest installation option, with minimised visual impact and risk of animal incursion to the installation assembly.

Conclusion

Connecting surge arrestors to reclosers are an essential component of reliable installation design. In this article we reviewed 3 options for this connection.

“Surge arresters are a sensible investment to protect the capital equipment and ensure lightning strikes are conducted to ground so the asset being protected does not experience impulses above its ratings,” says NOJA Power Group Managing Director Neil O'Sullivan.

The key engineering consideration is to minimise the distance between the surge arrestor terminal and the switchgear terminals. This is balanced against ease of field replacement, as seen in option one, or standardising on a surge arrestor height to achieve the neat installation with surge arrestor bars.

For more information, visit www.nojapower.com.au or contact your local NOJA Power Distributor.