Page 43 - Energize February 2022

TECHNICAL

Why specifying enclosed epoxy

insulation delivers better reliability

Information from NOJA Power

he goal of power systems engineers is to deliver reliable electricity, safely and Epoxy can be treated with additives,
sustainably, to their customers. In years past, our engineering predecessors which work to restore the surface integrity,
Twould specify the latest SF 6 gas insulated switchgear to achieve most of that goal. but these too are a finite resource. Once
Despite SF 6’s environmental damage, they would be forgiven in the context, as they had they are exhausted, the film reforms and
no alternative when choosing cost-effective switchgear. then breakdowns occur.
Today however, SF 6 insulation has been made obsolete by electrical grade solid
dielectric. This insulation is an advanced polymer that replaces the role of SF 6 in making How to avoid it
switchgear. Engineers can now specify solid dielectric as an insulation medium, but The best way is to play to the strengths of
there is a risk in specifying it alone. epoxy and to keep it away from sun and rain.
By enclosing the epoxy in stainless
The key risk is environmental factors steel and silicon, engineers mitigate the
Original epoxy insulation provides excellent insulation properties, but its resistance risk of accelerated environmental ageing
to the environment, particularly water, has been extensively researched and found of equipment.
wanting. The engineering problem is that over time, epoxy’s hydrophobicity (its water- Across the 104 countries and 75
repelling ability) degrades. This degradation accelerates in high UV, high rain, or high 000 installations of NOJA Power’s
pollution. OSM Recloser, not a single report has
While many materials scientists are working to address this shortcoming, the been made of environmentally-caused
fundamental weakness of solid dielectric insulation is environmental exposure risk. insulator failure.
Specifying solid dielectric insulation
What goes wrong enclosed in silicone and stainless steel is
Understanding the risk of exposed epoxy in switchgear is best understood with a a solid choice for choosing reliability in
diagram. Figure 1 shows this process. power and switchgear products.
When solid dielectric epoxy is fresh, water forms clear droplets, rather than a film. “Historically, the argument has always
Over time, environmental factors cause a reduction in this performance. Once a film of been: ‘Please don’t ban SF 6 gas use in
water can form on the material, breakdown accelerates. Eventually, electrical tracking medium voltage switchgear because
occurs, before final arc faults and insulation failure. we can’t make safe reliable switchgear
without it’,” says NOJA Power Group’s
managing director Neil O’Sullivan.
“The reality is that epoxy resin as the
insulation system instead of SF 6 gas has
been used for four decades successfully
and reliably. Combine that with an arc
fault contained and vented stainless steel
tank and you can make safe, reliable,
solid dielectric switchgear and completely
eliminate the use of SF 6 gas for medium
voltage applications. It’s time we do that
globally - particularly in the race to net
carbon zero by 2050.”

Contact NOJA Power,
sales@nojapower.com.au,
Figure 1 – Typical current trace for a generator terminal short circuit fault.
Kaltenborn, et al. © 2002 www.nojapower.com.au

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