Risk mitigation – Engineering *
A range of engineering measures can be taken to reduce the probability and/or the magnitude of an arc flash incident.
- Compliance with an Approved Code of Practice (ACOP) such as HSE publication HSG 230 “Keeping Electrical Switchgear Safe”
- Publication of a set of electrical safety rules and training personnel in correct application of the rules. Electrical isolations and control of live working are of particular importance.
- In the case of new installations equipment can be specified to reduce the risk of incidents e.g. fully insulated bus bar system and to improve safety in the event of an incident e.g. venting
- Existing equipment can be retrofitted with remote operation facilities
- Where practicable fault levels can be reduced by, for example, opening bus coupling switches, fitting reactors or fast acting fuses.
- Protection operating times can be reduced to clear faults more quickly and reduce arc energy levels.
- Arc detection and suppression devices can be fitted to quickly sense and quench arcs.
* Source: TAS Engineering
What does an arc flash study tell me?
“An arc flash study will tell you the incident energy due to the flashover and in simple terms this means - how big is the bang? Most importantly there will be an evaluation which will highlight those cases of low risk, those which will need other protective measures and those areas where there is great danger to workers who engage in live working activities.
The study will evaluate the severity of injury at a given distance from the arc and the flash protection boundary at which distance there will be the onset of 2nd degree burns. This gives designers and facilities managers a scientific basis for the evaluation of the working space in front and around switchgear. It will also give warning label requirements to state the arc flash hazards, boundaries and PPE requirements.
By carrying out an arc flash study to IEEE1584 you will also know the fault levels throughout the facility and therefore assess the capability of equipment to withstand short circuit currents. The ability to calculate Flash Protection Boundaries will enable managers to arrive at better-informed judgements before allowing live proximity work to proceed in the first place and provide an ability to apply quantitative techniques to risk control. There is software available but only trained individuals should undertake arc flash calculations, as any study should take account of variables due to system configuration for example”.