9.1.1 Safe People Checklist
- Information, training and instruction. A good risk assessment methodology will assist greatly in providing awareness, information and an understanding of the hazards.
- Competence assessment. Personnel have a key role in arc flash risk management. All the factors that are outlined in Chapter 6: Process, Policies and Procedures about competence assessment, will help to establish safe people and prevention strategies. In addition, to have named electrical safety ambassadors at the level of operative works well to achieve focus and to influence colleagues and contractors.
- Contractor competence. Make sure that all contractors are competent at tender evaluation. From my experience, there are a disproportionately high number of arc flash incidents among contractors. As highlighted previously, control of contractors specifically down to the level of confirming the competence of their personnel is required.
- Specific authorisations. As mentioned previously, operatives who have clear boundaries, and are authorised through a rigorous assessment of competence, are less likely to carry out high risk activities involving live equipment.
- PPE. The provision of personal protective equipment is a last resort but it is necessary that correct PPE is provided and worn. See Chapter 7: Protection. Any PPE must not create other hazards, such as severe sensory deprivation so this is why the 4P approach is so important.
- Supervision and control. Wherever mitigation procedures are put in place, whether PPE or rules, it is essential to ensure that these measures are being practiced by personnel. Supervision and leadership backed by auditing processes will ensure that what is put in place in theory, actually happens in practice.
9.1.1 Safe Places Checklist
- Well-designed installations. Having installations that are designed in accordance with best practice and take into account the techniques highlighted in Chapter 5: Prevention & Minimisation.
- Well maintained installations. An electrical maintenance program is required to keep electrical equipment in good working condition so that it can reliably and safely operated within its design criteria. Improper maintenance of equipment can increase the likelihood and/or contribute to the severity of an arc flash.
- Confidence in protection systems. Testing and maintenance of circuit breakers, protective relaying and associated equipment on a regular basis. When a protective device such as a circuit breaker or relay is not properly maintained, the likelihood of it operating slower (or not at all) increases, which would also increase the duration of exposure to the arc flash.
- Organisation of Documentation. Having an organised library incorporating design information, test data, commissioning information, grading and fault level studies, technical manuals, asset directory, manufacturer’s operating manuals and instructions, periodic test and inspection reports is essential. This is often overlooked as a key ingredient in electrical safety management.
- Fires from electrical arcing. Although not the main subject of this guide, there is evidence that the largest cause of fires in non-residential premises is due to electrical faults and an estimated 50% of these are arcing faults. For high-risk systems or areas consider arc fault detection as enhanced protection and most importantly, well designed and maintained electrical systems.
- Carry out a system study including an arc flash hazard assessment. This can be the catalyst for addressing many of the points detailed above.
9.2 System Study
The last item on the above checklists is about carrying out a system study including an arc flash hazard assessment. This section gives advice on how to recognise whether the information that you have on your electrical system is sufficient and if not, how to improve or correct the situation.
In my view, a study should not be with the single aim of creating incident energy levels in order to specify PPE. To carry out a study of an electrical system provides a perfect opportunity to take stock and to establish whether or not the design of the electrical system matches the present condition, and also to highlight serious deficiencies in operation and maintenance. One such example of what is meant here, is the highlighting of unauthorised modifications to switchgear and electrical panels which, effectively convert a safe piece of equipment into something that is unsafe and potentially lethal. I remember creating a gallery of horrors from photographic images, where such modifications were widespread on one particular site. The embarrassment of the duty holder was palpable as we went through slides showing numerous unauthorised modifications to equipment. One was almost comical, showing a five-gallon chemical drum that had been cut in half to replace missing insulation over an internal process panel isolator.
9.2.1 Expectations from a system study?
A network diagram or a single line diagram. An accurate schematic of the electrical system is essential for a high voltage system but is also important for high power low voltage networks and is a reference document for the planning, coordination and control of work activities.
Fault level study. A fault level study will give prospective fault current level and information about the capability of switchgear. Things change over time meaning that fault currents can change because of characteristics of the electricity supply, embedded generation and system configuration. Whilst we are looking for the worst-case fault current available at the various connected electrical equipment, we need to also ensure that we understand the normal fault currents in order to determine incident energy levels. The worst-case fault current will determine the strength and capability of connected equipment to ensure that it will not fail during a fault clearance. The study will take into account mains connections, embedded generators and also other fault contributors such as induction motors.
Protection Coordination Study. Any changes to characteristics of the electricity supply, embedded generation and system configuration can require that protection arrangements are reviewed. As the name suggests, the study will ensure that the electrical system will react to faults in a predictable manner and will determine the length of time that a fault takes to clear. In order to calculate incident energy, the coordination study is necessary to determine the clearance time of arcing currents.
Arc Flash Incident Energy Study. The arc flash study is designed to calculate the arc flash hazards at a distance called the arc flash boundary and the incident energy that a worker could be exposed to when working on or near live equipment. I have calculated that the amount of effort that is required to carry out an arc flash study is about 10% of the total when conducting the creation of a single line diagram, fault level study and a protection coordination study. That is, bearing in mind that any self-respecting engineer would advocate the latter three outputs to be essential to electrical system management.