Medium Voltage Fuses Are Not Fail-Safe: Candling Failures Pose Wildfire Risk

As utilities worldwide strive to improve grid reliability and reduce wildfire risk, new attention is being drawn to the limitations of traditional medium voltage fuses. While fuses have long been a staple in electrical protection systems, they are not inherently fail-safe.

A particularly hazardous failure mode known as candling has emerged as a significant concern for utility operators and fire mitigation experts.

Candling occurs when a fuse fails to interrupt fault current properly, instead sustaining a low-energy arc that burns slowly, similar to a candle. This unsafe failure mode can result in molten material or sustained arcing, which poses a serious ignition hazard, especially in dry, vegetation-rich environments.

According to utility asset management strategies submitted by Australian utilities to the Australian Energy Regulator, candling is a recognised failure mode in medium voltage fuse switch disconnectors and has been linked to bushfire ignition risks.

Despite the widespread use of fuses, their inability to guarantee safe disconnection under all fault conditions—especially in rural and remote areas—has prompted calls for safer alternatives. The NOJA Power EcoLink®, a fuse-link mounted single-phase recloser, offers a transformative solution.

Unlike traditional fuses, EcoLink features an internal vacuum interrupter (VI) that is interlocked with the manual handle. This design ensures that any disconnection is performed internally, significantly reducing the risk of external arcing or sparks during removal.

The EcoLink also provides reclosing capability, allowing it to clear transient faults, faults that would otherwise result in permanent outages when protected by a fuse. With approximately 80% of overhead line faults being transient, this feature alone offers substantial reliability improvements.

In many cases, a single outage prevented by a NOJA Power EcoLink will recover the cost of the EcoLink.

Additional benefits of the EcoLink include:

• Self-powered operation from as low as 0.15 A of primary current
• Rapid fault interruption using rate-of-change detection
• Wireless configuration with IEEE 1686 cybersecurity compliance
• Lightweight design (approx. 7.4 kg) for safe and easy installation
• All-weather durability, rated from -40°C to +55°C
  

“EcoLink is one of the most innovative products we've developed,” said Neil O'Sullivan, NOJA Power Group Managing Director.
“It solves many of the problems our customers face with fuse replacement, especially in fire-prone regions.”

As utilities face increasing pressure to harden their networks against wildfire threats, the limitations of medium voltage fuses, especially their unsafe failure modes, must be addressed. EcoLink represents a safer, smarter path forward, combining advanced protection with operational reliability.

For more information, visit www.nojapower.comor contact your local NOJA Power Distributor.