12.3 – Table F.2 – Likelihood of Occurrence of Arc Flash

Factors that affect the likelihood of occurrence of an arc flash incident.

The two components of risk are the likelihood of occurrence of injury or

damage to health and the severity of injury or damage to health that results from a hazard. Risk assessment is an overall process that involves estimating both the likelihood of occurrence and severity to determine if additional protective measures are required.

The purpose of Table F.2 is to provide guidance to estimate the likelihood of occurrence of an arc flash for specific tasks performed in specific conditions. This Table cannot and does not address every possible task or condition, nor does it address the severity of injury or damage to health. Where the likelihood of occurrence is identified as “improbable”, it does not mean that it is impossible. Where the likelihood of occurrence is identified as “possible”, it does not necessarily mean that it is probable. 

What is ‘NORMAL’ Equipment Condition?

The risk assessment procedure shall include determining whether a normal equipment condition exists.

A normal equipment condition shall be considered to exist when all of the following conditions are satisfied:

1. the equipment is properly installed;
2. the equipment is properly maintained;
3. the equipment is used in accordance with instruction included in the applicable Canadian Electrical Code, Part II, standard and in accordance with the manufacturer’s instructions;
4. all equipment doors are closed and secured;
5. all equipment covers are in place and secured; and
6. there is no evidence of impending failure.

If Determining Likelihood proves Possible (TRUE) then you need to continue to select appropriate PPE.

When table F.2 suggests likelihood is possible, continue to tables V.1 or V.2 for AC Systems, table V.3 for DC Systems.

Alternating current equipment types, voltage classifications, and parameters are listed in Table V.1 and the associated notes. Table V.1 shall not be used where the listed parameters are exceeded or for equipment types and classifications that are not listed.

The parameters of estimated maximum available fault current, maximum fault clearing times, and minimum working distances for various ac equipment types or classifications are listed in Table V.2. Table V.2 shall not be used where the listed parameters are exceeded or for equipment types and classifications that are not listed.

If you cannot use Table V.1 or V.2 for AC Systems then,
incident energy analysis must be used.