An Arc Flash study is a specialist risk assessment that identifies all areas of risk, however high or low, within a working environment, and determines the level of the Arc Flash hazard.

An Electrical Arc Flash Study is not specifically identified in UK Legislation, but OSHA 1910.132 requires employers to identify and protect their employees from workplace hazards. While an Arc Flash study is not specified as compulsory, it is objectively true that there is a level of risk any time employees are interacting with energised electrical systems. It is impossible to know what level of arc flash hazard risk is inherent in your power system without analysis by a suitably qualified electrical specialist. Therefore, in order to perform a fully compliant risk assessment, an arc flash study is required.

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To claim your FREE Arc Flash Pre-Assessment, please complete the form below and an ESUK representative will get in touch with you to arrange this.

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Arc Flash Risk Assessment– What does it involve?

ESUK explain their risk assessment process below:

“We start by looking at the hazard, in this case arc flash hazards. For each piece of equipment on our electrical network we need to work out what the worst-case arc flash hazard is. We quantify the hazard by calculating the “incident energy” level for each piece of equipment. Incident energy is defined as: “The amount of thermal energy impressed on a surface, a certain distance from the source, generated during an electric arc event”. Incident energy can be expressed in a number of units but typically it is quoted in calories/centimeter2 (Cal/cm2) for the simple reason that arc flash personal protective equipment is normally rated in Cal/cm2.

We also need to consider what activities we are carrying out on that equipment. We should consider whether an arc flash can occur and if we can be exposed to it, should it occur. We can then look at putting control measures in place to reduce the risk to an acceptable level. We may decide we need to wear arc flash PPE. The incident energy level for the equipment we are working on, will determine what level of protection we need the arc flash PPE to provide.”

Paul Hopton – Principal Consultant

How is Incident Energy Calculated?

ESUK have carried out hundreds of arc flash studies

The electrical network is modeled in software in order to determine the incident energy levels for each piece of equipment on the network. This is normally done for all three phase (3Φ):

  • High Voltage (HV) circuits
  • Low Voltage (LV) circuits rated at:
    • ≥100Amp when protected by a fuse
    • ≥63Amp when protected by a circuit breaker

Note: ESUK can demonstrate that LV circuits protected outside these parameters are below the low hazard threshold of 1.2 Cal/cm2 and therefore do not need to be included in the scope of the study. Typically this means nearly all the final circuits are excluded from scope and the cost of the study is significantly reduced when compared to an assessment of all three phase LV circuits.

Arc Flash Risk Assessment– What does it involve?

STEP 1: Collect electrical system data, typically:

  1. SLDs – System one-line diagrams
  2. EICR – Fixed wiring inspection and test reports
  3. Electric utility source information
  4. Ring Main Unit/Switchboard/Load Centre/Distribution Board information
  5. Details of all voltage sources: e.g. generators, wind turbines, solar panels and large motors
  6. Details of all reactors, capacitors and transformers
  7. All conductor types, sizes and lengths
  8. Protective device information – protection relays, fuses and circuit breakers: brand, model, settings, CT ratios etc.

STEP 2: Build a model of the network in software.

STEP 3: Carry out a short circuit study.

STEP 4: Calculate the Incident Energy Levels and Boundary Distances on each piece of equipment.

STEP 5: Check protection discrimination.

STEP 6: Label the equipment with the calculated incident energy, arc flash boundary distance and recommended Personal Protective Equipment (PPE) for the specific piece of equipment.

STEP 7: Reduce the arc flash incident energy levels (for incident energy levels >8Cal/cm2 and if reasonably practicable).

STEP 8: For equipment that is >8 Cal/cm2 after the incident energy reduction work has been completed in the previous step, carry out task-based arc flash risk assessments. These risk assessments determine what activities are carried out on the equipment and for each activity whether control measures can be put in place to mitigate the risk, including the use of arc flash PPE.

STEP 9: Train your staff to understand Arc Flash Risk and what is required of them to stay safe. Explain the labelling and PPE requirements.

STEP 10: Ensure visitors and contractors are appropriately briefed on what they are required to do.

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