Why are Arc Flash Studies important?

Arc flash studies allow one to predict/quantify/estimate the severity of the potential risk presented by an arc flash hazard, specifically the thermal effects of the hazard.

An incident energy analysis is performed using electrical power system analysis software to determine  the Estimated Incident Energy (1), and a corresponding  Arc Flash Boundary (2) at each location in an electrical network.

Arc flash hazard warning labels can then be produced and affixed to equipment to show the level of risk and the required level of arc-rated clothing and personal protective equipment (PPE) that should be worn by electrical workers working on or in the vicinity of the equipment.

It should be noted that PPE recommendations based on incident energy analysis are the last line of defence against arc flash hazards. Other mitigation measures provide the first line of defence and should be employed in the first instance, such as;

• Engineering controls
  • De-energise electrical equipment before working on or near it.
  • Keeping workers at a safe distance from live equipment (e.g. installing remote operating devices to reduce the need to operate switches whilst close to equipment).
  • Installing arc-resistant switchgear or equipment designed to redirect, contain or extinguish an electrical arc.
  • Using fast operating protective devices to reduce fault clearance times.
  • Using current-limiting fuses to reduce the energy releases during an arcing fault.
• Administrative controls
  • Developing and enforcing electrical safety policies, procedures and protocols for conducting work on or near energised equipment, including risk assessments and work permits.
  • Providing comprehensive training for workers.
• Regular inspection, testing and maintenance of electrical equipment

Key Challenges Involved in Arc Flash Studies 

• Collecting requisite data – some equipment data can be difficult to obtain and therefore engineering judgement is needed to employ appropriate assumptions.

• Modelling complexity – meshed networks consisting of multiple electrical sources and the various operating scenarios of networks can add to the complexity of arc flash hazard analysis. Engineering expertise is needed to select scenarios which represent the largest potential incident energy exposure. A thorough knowledge of protection co-ordination schemes is required.

• Dynamic operating conditions – capturing dynamic operating conditions (e.g. loading changes, switching operations and transient events) in arc flash studies entails detailed modelling and analysis.

• Arc flash calculation – calculating arcing current and incident energy involves complex equations that depend upon equipment characteristics, fault current levels, system impedance and protective device coordination. Power engineering expertise is essential in ensuring careful consideration of the many assumptions and parameters involved in this process.

• Accessing equipment – accessing electrical equipment for data collection, testing or maintenance can pose safety risks.

• Regulatory compliance – thoroughly understanding the requirements of the relevant standards and regulations and adhering to best practices is essential.

• Skills and resources – arc flash hazard analysis requires specialist engineering expertise and knowledge, modelling software and potentially equipment testing capabilities.

View industry standards on our Standards, Regulations and Resources page.

1. Estimated Incident Energy is the thermal energy, measured in calories per square centimetre or Joules per square centimetre, that a worker could potentially be exposed to at a given distance from the source of an arc flash.

2. Arc Flash Boundary is a distance from an arc source at which incident energy is calculated to be 1.2 cal/cm² or 5.0 J/cm², the threshold for a second-degree burn.

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