Jim Phillips, P.E.
There is more to an arc flash risk assessment than calculations, arc flash labels and making PPE recommendations. Avoiding, Reducing or Eliminating the arc flash risk is a critical first step. This often involves reducing the duration or increasing the distance between the prospective arc flash and the worker. A few of these methods include:
Arc Resistant Equipment
Equipment such as switchgear and motor control centers can be specially designed so the operator can perform switching or “racking” a circuit breaker in or out while standing in front of the equipment. If an arc flash occurs, the energy and debris will be contained within the equipment and vented through a channel away from the worker.
Current Limiting Devices
Current limiting fuses and circuit breakers can greatly reduce the amount of incident energy by reducing the duration of the current, its magnitude, and resulting thermal energy.
Protective devices with an arc energy reduction switch can be used which provides a function to temporary enable high speed device settings that can reduce the incident energy.
Remote operation uses a motorised unit mounted on a movable frame that operates, inserts or removes the protective device keeping the worker at a safe distance and reducing the incident energy exposure.
Optical Detection and High Speed Clearing
Sensing both the ultraviolet light and the resulting overcurrent can be used to identify that an arc flash has occurred. Then, the protective device within the arc flash zone is operated in its high speed instantaneous region to reduce the arc flash duration and incident energy.
For protection from any residual risk, visit www.arcflashprotection.co.uk The best solution is to only work on equipment that is placed into an electrically safe work condition. Only then is the system truly safe to work on.