Electrical Safety Risk Assessment (Page 2 of 6) in pdf

2. Frequency and Duration of Exposure (Fr) - The following aspects should be considered to determine the level of

exposure:

a. Need for access to the hazard zone based on all modes of use; for example, normal operation and

maintenance

b. Nature of access, for example, examination, repair, and troubleshooting.

Choose the appropriate Frequency value from Table 2 below. Add value to the Risk Register (Table 5)

Frequency of Exposure

Fr Value (for Duration > 10 min)

< 1 per hour

> 1 per hour to < 1 per day

> 1 per day to < 1 every 2 weeks

> 1 every 2 weeks to < 1 per year

> 1 per year

Table 2

3. Likelihood of Occurrence of a Hazardous Event (Pr) – The occurrence of a hazardous event influences the

likelihood of the occurrence of injury or damage to health. The possibility of the hazardous occurring should

describe the likelihood of the event materializing during the use or foreseeable misuse, or both, of the electrical

system or process. Subjectivity may have a substantial impact on the result of the risk assessment. The use of

subjective information should be minimized as far as reasonably practicable.

The likelihood of occurrence of the hazardous event should be estimated independently of other related

parameters (Fr and Av) and will typically be based on the results of the completed study of the arc flash potential.

The worst-case scenario should be used for this parameter to ensure that short-circuit interruption device(s) have,

where practicable, been properly selected and installed and will provide adequate protection.

Elements of the electrical system that are intended to ensure an intrinsically safe design shall be taken into

consideration in the determination of the likelihood of the hazardous event(s). These can include, but are not

limited to, the mechanical structure, electrical devices, and electronic controls integral to the system, the process,

or both at the time of the analysis. Types of components that could contribute to an inherently safe design include,

but are not limited to, current-limiting devices and ground-fault circuit interrupters.

This parameter can be estimated by taking into account the following factors:

a. The predictability of the performance of component parts of the electrical system relevant to the hazard in

different modes of use (e.g., normal operation, maintenance, fault finding).

At this point in the risk assessment process, the protective effect of any personal protective equipment

(PPE) and other protective measures should not be taken into account. This is necessary in order to

estimate the amount of risk that will be present if the PPE and other protective measures are not in place

at the time of the exposure. In general terms, it must be considered whether the electrical system being

assessed has the propensity to act in an unexpected manner. The electrical system performance will vary

from very predictable to not predictable. Unexpected events cannot be discounted until it can be clearly

demonstrated that the electrical system will perform as expected.

b. The specified or foreseeable characteristics of human behavior with regard to interaction with the

component parts for the machine relevant to the hazard, which can be characterized by one or both of the

following:

i. Stress (e.g., due to time constraints, work task, perceived damage limitation).

ii. Lack of awareness of information relevant to the hazard.

Human behavior will be influenced by factors such as skills, training, experience, and complexity of the machine

or the process.

These attributes are not usually directly under the influence of the electrical system designer, but a task analysis

will reveal activities in which total awareness of all issues, including unexpected outcomes, cannot be reasonably

Electrical Safety Risk Assessment Page 2

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