Risk Control
When the assessment results in high risk situations for personnel, risk control measures should be evaluated to reduce the risk of those situations.
The hierarchy of controls is a system widely used in safety engineering to ensure that passive solutions at the source are put in place before personal protective equipment.
Elimination is the most effective type of control measure that aims to eliminate the risk altogether. If possible, not performing the work is the most effective way to avoid exposure.
If distribution equipment is no longer in use but remains energized some work activities such as maintenance may still need to happen. If the risk is determined to be high on equipment that is obsolete, removing the equipment also removes the risk.
Substitution of the original risk with a reduced one should be investigated if it cannot be completely eliminated. These measures must be passive and collective: the safety they provide should apply to everyone without requiring additional actions or precautions to be taken.
Older distribution equipment may have inadequate guarding of circuit components. Replacing the equipment or installing IP2X rated shielding reduces the risk of work where access to circuit parts is not necessary such as inspection or switching.
Electrical distribution equipment that is tested to be an arc proof assembly can contain the electrical arc, reducing the risk for employees. These tests are performed under specific circumstances, most notably that equipment doors are closed and secured. For tasks that meet these conditions the risk is reduced.
Engineering solutions provide reduction in risk through technical changes that reduce risk at the source.
High settings of circuit breakers are a common cause of high hazard that can be resolved by lowering settings. Sometimes the type of protection is inadequate, for example when fuses or breakers that are not adjustable are installed. In most cases these can be replaced by a breaker that has an adjustable protection unit.
Care should be taken that new settings or devices do not lead to unwanted tripping or miscoordination of other protection devices. A load analysis and protection coordination study can help in the selection and application of appropriate settings.
When detection of arc flash is an issue due to low fault currents, devices that detect the arc’s flash of light can be used. Although detection is very fast, the system still relies on breakers to interrupt the fault. When protective devices and their settings are correctly chosen the potential for hazard reduction is limited.
If permanent setting changes would result in unacceptable consequences for system stability or protection coordination, a maintenance switch can be considered. A maintenance switch provides switchable lower protection settings for a circuit breaker. Activating the switch temporarily lowers the hazard at the desired location.
Where multiple sources can feed into distribution equipment an interlock preventing parallel operation can reliably reduce hazard. When paralleling is desired from an operational perspective, an automatic transfer system that limits the parallel situation to a few seconds can be used.
Administrative solutions are control measures that rely on the employee’s skill and knowledge to create a safe work environment.
Voltage testing is an activity where potential exposure to arc hazard is unavoidable. For locations with a high hazard that cannot be lowered through engineering controls the arc risk can be reduced by performing a backup measurement to confirm that the equipment is de-energized.
To increase and maintain personnel awareness of the risks of electrical arcs, training should be provided to anyone who might be exposed to them. Especially outside of NFPA 70E jurisdictions, training for electrically qualified personnel most likely does not include arc risk.
Personal Protective Equipment (PPE) can be used to mitigate arc hazard for any residual risk. More and heavier PPE is required for higher levels of incident energy to which the worker is potentially exposed.
