Paul Hopton, Deputy Managing Director and Principal Electrical Consultant, discusses when Arc Flash Protection is required, carrying out Risk Assessments to determine the requirement and suitable competency of those involved.
Before you can make any sensible decisions about when arc flash protection is required, you will need to know the level of arc flash hazard you could be exposed to. An arc flash study calculates the maximum potential arc flash hazard (incident energy level) on each piece of equipment on the electrical network. Knowing the incident energy level for the equipment you will be working on is a pre-requisite to risk assessing the hazard. If you do not know the level of incident energy you are facing, you are left with isolating the equipment before working on it or wearing arc flash personal protective equipment (PPE) with a high protection rating. You could be criticised under current legislation for wearing PPE without carrying out a risk assessment. The wearing of arc flash PPE should always be minimised for a number of reasons but including that the PPE can significantly affect your senses: sight, hearing, touch and smell, and your ability to communicate clearly. This is not a good thing when you are working with electricity, so you really only want to be wearing PPE when you need to.
The short answer to the question: “When is arc flash protection required?” is when personnel are carrying out an activity on electrical equipment that could expose them to an arc flash event of 1.2 Cal/cm2 or greater. Fortunately, many of the activities carried out on electrical equipment do not have the potential to expose personnel to significant arc flash risk. However, some of the activities that are carried out, do expose personnel to significant risk and adequate control measures need to be put in place to prevent serious injury or fatalities.
If an arc flash occurs that has an incident energy of less than 1.2 Cal/cm2 then the likelihood is that if you were exposed to that event, you may end up with at worst, a first-aid type injury. If we then consider the likelihood of an arc flash occurring, from a risk perspective we have:
- A low consequence – first-aid type injury at worst
- A low likelihood of the event occurring – typically 10-6 or once a year in your industry
Therefore a low risk can be considered acceptable.
What about arc flash events >1.2 Cal/cm2
If personnel are carrying out an activity on electrical equipment that could expose them to an arc flash event >1.2 Cal/cm2 but <8 Cal/cm2 then we would look to control the hazard though operational, engineering, or other control measures. If there was not a relatively easy to implement,
low-cost control measure available to us, then we would recommend the use of arc flash PPE to control the hazard. We should consider that PPE rated at 8 Cal/cm2 would not significantly affect the wearer’s senses and ability to communicate when compared to 40 Cal/cm2 arc flash PPE. Typically, 8 Cal/cm2 arc flash PPE would look something like the following image.
What about arc flash events >8 Cal/cm2
If personnel are carrying out an activity on electrical equipment that could expose them to an arc flash event greater than 8 Cal/cm2 then we recommend carrying out a task-based risk assessment. Above 8 Cal/cm2 we consider that the risk is sufficiently high to justify the additional effort of completing a more detailed risk assessment. We have developed a comprehensive risk assessment methodology. That methodology can be learnt by attending our Practical Arc Flash Risk Assessment Training Course (click for further information).
Below is an outline of what our task-based risk assessment involves:
The first step in the risk assessment process looks at the design of the equipment that the activity is going to be carried out on. We consider:
- Operating context: voltage, location…
- Switchgear details: Manufacturer, enclosure type, insulating material…
- Form of construction and ingress protection rating
- Equipment rating
- Arc Flash Details: Incident Energy Level, Arc Flash Boundary Distance…
The next step is to consider in more detail the operating context of the switchgear and enclosure:
- Integrity of switchgear
- Built-in arc flash safeguards
- Failure and operating history
The first two steps in the risk assessment process completed above should give us the right level of background information to allow us to start risk assessing the activities carried out on the switchgear. We consider a number of generic type activities that could be carried out on the switchgear, some examples of which are:
- Switchgear operation with enclosure doors closed
- Work on energised parts, including voltage testing
- Work on control circuits with energised parts > 115 V, exposed
- Insertion or removal (racking) of Circuit Breakers from cubicles, doors closed and open
We also consider any other activities that are carried out on the switchgear which we may not have included in the generic activity list in our arc flash risk assessment template.
For each activity we consider:
- the risk of an arc flash occurring whilst the activity is being carried out
- whether there are any increased risk factors that we need to take into account
- what control measures we can put in place without relying on arc flash personal protective equipment
- Finally, whether arc flash PPE is required and what rating the PPE needs to have
The final part of the risk assessment looks specifically at operation and the operator’s experience of working with the equipment. It might sound a bit obvious, but speaking to the personnel that work day in/day out with the equipment, and finding out how they feel about working with the equipment can be very illuminating.
On completion of the risk assessment, we would recommend keeping a paper copy displayed on the equipment. Anyone working on the equipment can pick up the risk assessment, review it and make an informed decision about the activity they will be carrying out on it.
Where do we start?
If you would like more information or help in carrying out an arc flash study and risk assessments, why not get in touch with us. There is no charge for our initial pre-assessment visit. We would be happy to come and see you to discuss your requirements and if required provide you with a fixed-price, no obligation proposal.