Electrical hazards are often invisible—and deadly. While qualified electricians understand the risks, most electrical injuries and fatalities occur among non-electrical workers performing routine tasks like operating machinery or cleaning equipment. According to U.S. Bureau of Labor Statistics data, an average of 150 deaths and nearly 2,000 serious injuries occur annually due to electrical exposure, and 64 per cent of these fatalities involve non-electrical occupations.
In mining environments, where high-voltage equipment and harsh conditions are the norm, traditional safeguards, such as personal protective equipment (PPE) and awareness training, are not enough. These measures rely heavily on human behaviour, which is prone to error. Instead, the industry needs proactive engineering controls—solutions that eliminate hazards before they reach the worker.
From GFCIs to SPGFCIs: A new layer of protection
Ground-fault circuit interrupters (GFCIs) have been saving lives for decades in residential and commercial settings. They detect leakage current and trip the circuit to prevent electrocution. However, standard Class-A GFCIs are designed for low-voltage applications (typically 120 or 240 V) and trip at 6 mA or less. In mining, where equipment often operates at higher voltages and currents, these devices are not practical.
Enter Special-Purpose GFCIs (SPGFCIs)—a technology that gained recognition when it was added into the 2023 National Electrical Code (NEC) in the USA. SPGFCIs extend personnel-level protection to circuits up to 300 V to ground (Class C) and above 300 V (Class D), with trip thresholds up to 20 mA to prevent ventricular fibrillation. More importantly, SPGFCIs incorporate a Ground Monitor/Interrupter (GM/I) function, which verifies the integrity of the equipment grounding conductor before energizing the circuit and continuously monitors it during operation.
Why is this critical? If a ground conductor is damaged or missing, a standard GFCI will only trip after a person completes the fault path—meaning the worker experiences a shock. SPGFCIs with GM/I isolate the hazard before anyone touches the equipment, preventing the incident entirely.
Prevention through design
The concept of Prevention through Design (PtD) emphasizes eliminating hazards at the source rather than relying on administrative controls or PPE. SPGFCIs embody this principle. By integrating ground monitoring and higher trip thresholds, they address two major challenges in mining:
– Industrial Loads: Traditional GFCIs cannot handle the leakage currents common on industrial circuits which contain large motors and variable frequency drives.
– Harsh environments: Wet conditions, damaged cords, and temporary wiring increase shock risk. SPGFCIs proactively detect these issues.
For example, consider a portable pump on a trailing cable. If the ground conductor breaks, a standard GFCI may not trip until a worker touches the energized frame. An SPGFCI with GM/I prevents the pump from energizing in the first place.
Applications in mining
Mining applications already have requirements to have ground monitoring (also called ground check) for some portable loads. SPGFCIs meet CSA M421 ground-check requirements and should be considered for:
– Portable and temporary equipment used in construction or maintenance.
– Industrial loads where Class-A GFCIs are impractical.
– Locations with frequent ground conductor damage or harsh environmental conditions.
These devices align with CSA Z462 and NFPA 70E[1] principles for electrical safety and support the hierarchy of risk controls by implementing engineering solutions rather than relying solely on human behaviour.
The bottom line
Electrical shock incidents in mining are preventable. By adopting SPGFCIs with ground monitoring, operators can move from reactive protection to proactive hazard elimination. This technology represents a significant step forward in designing safer workplaces, especially for non-electrical workers who remain the most vulnerable.
As the industry embraces electrification and automation, integrating SPGFCIs into equipment design
[1] Informative Annex O: O.2.4 (12) mentions that Class C, D, and E special purpose ground fault circuit interrupters exist for circuits operating at voltages outside of the range for Class A GFCI Protection.
