NFPA 70E defines “risk” as the combination of two components: one is the likelihood of an occurrence of injury and the other components is the severity of the injury that results from the electrical hazard.
The risk assessment process includes the following:
- Identify the hazard (from both a shock and arc flash perspective)
- Estimate the potential severity of the injury
- Estimate the likelihood of the injury occurring
- A determination if protective measures are required (rubber glove, for example)
- Potential of human error
2018 NFA 70E added Annex Q to introduce the concept of human performance and how it can be applied to electrical safety and error prevention.
The negative consequences of human error on both people and the work environment/equipment must be taken into account as part of the electrical safety program’s risk control procedures.
Also new for 2018 is the requirement that the electrical safety program must follow a “hierarchy of controls” when controlling risk. This hierarchy prioritizes the elimination of the hazard as the first priority.
For electrical hazards, this typically means eliminating the need for someone to be exposed to energized parts. It also means one should de=energized equipment and create an electrically safe work condition before starting the work, which eliminates the hazards.
When hazard elimination is not possible the next priority is substation. For example this may mean utilizing 24 V DC as opposed to 125 V DC. The third risk control is engineering controls. There are many engineering controls, such as maintenance mode switch (to reduce the arc flash hazard before starting work) to high resistance grounding systems instead of solidly grounded systems to bring the available fault current down.
The fourth risk control is awareness and administrative controls. Signage to restrict access and training are two examples. The last risk control method is PPE for the employee. This is the last choice in the hierarchy of controls but necessary for example to establish an electrically safe work condition.