SUMMARY

Winstone Aggregates Quarry operates motor control centres (MCCs) and switchboards that, like many industrial environments, present significant arc flash hazards. These hazards can lead to devastating outcomes such as explosions, severe burns, equipment damage and extended operational downtime.

Under AS/NZS 4836:2011 and Electrical Safety Regulation 100, arc flash is recognised as a serious risk within the framework of New Zealand’s Health and Safety at Work Act (HSWA). Fault currents during an arc flash event can surge up to 20 times the rated current, generating incident energy levels that may exceed the protective capabilities of standard personal protective equipment (PPE). The potential consequences of such an event at Winstone Aggregates include:

• Fatal or life-altering injuries
• Complete destruction of MCC infrastructure
• Prolonged plant downtime with multimillion-dollar losses

Personnel were routinely required to open panel doors to access insulated bus assemblies for isolating or resetting motor overloads and breakers — tasks that carried significant risk. Athenry implemented robust safety procedures to protect staff and ensure full compliance with regulations.