What is an electric arc?
An electric arc occurs when a discharge is sustained through a medium that normally acts as an insulator, such as air, after it has ionized. It can be part of a controlled process, such as certain welding techniques, or arise unexpectedly in an installation. This fact sheet focuses on accidental arcs that can affect people during electrical operations or work in close proximity.
The danger is not limited to the passage of current through the body. The released energy can cause burns, affect vision or hearing, and project materials. It can also cause reaction movements, falls, and fires. Therefore, it must be distinguished from direct or indirect electrical contact, although both risks may coexist during the same task.
In what situations might it appear?
An operation can alter insulation conditions or introduce an unforeseen conductive path. The presence of tools, contamination, deterioration, faulty connections, or equipment failures are circumstances that must be considered when evaluating the work. Knowing the nominal voltage is not enough; it is necessary to analyze the installation and the specific action to be performed on it.
The maneuvers, checks, and preparation phases may require special attention because the installation is not yet in the condition required for de-energized work. Equipment with known defects or abnormal operation must also be checked. Routine and repeated tasks do not guarantee that exposure is controlled or that protective devices maintain their initial performance.
What determines its consequences?
The energy that can reach a person depends on factors such as the available current, the duration of the arc, and the distance, as well as the equipment configuration and other scenario parameters. Therefore, it is incorrect to classify the hazard solely as “high” or “low” voltage. Low-voltage equipment can produce an arc with serious consequences.
The assessment must use a method appropriate to the type of installation and be aware of its limitations. A result calculated with incorrect data on protections or response times can lead to an inappropriate selection of measures. When settings, transformers, power supplies, or equipment are modified, it must be reviewed whether the previous assessment still accurately reflects the operating and maintenance conditions.
Prioritize eliminating exposure
In Spain, Royal Decree 614/2001 establishes that work involving electrical hazards must be carried out without power as the general rule, with the regulated exceptions. Planning should examine whether it is possible to avoid exposure before resorting to measures that only limit its consequences. Continuity requirements must be analyzed within the applicable framework and not become an automatic justification.
The five golden rules explain the steps involved in preparing for de-energized work. Disconnecting power is one of them, but it doesn’t complete the process on its own. Until the necessary conditions are established and verified, operations must be carried out using the procedures, resources, and protective measures defined for any remaining risks.
Collective protection and personal equipment
Design, maintenance, safeguards, and remote operation capabilities can all contribute to risk control when appropriate to the situation. Their selection requires technical analysis. A modification aimed at reducing response times, for example, must also verify the system’s coordination and functionality, avoiding simply transferring the problem to another part of the installation.
Personal protective equipment (PPE) is selected based on the assessment and required performance. Arc flash protection and electrical contact insulation are not interchangeable properties. The entire equipment package, its compatibility, condition, fit, and intended use must be considered. A garment chosen solely for its appearance or generic durability does not guarantee adequate protection in the intended scenario.
Practical example
A company is preparing for maintenance work on a switchboard. Before authorizing it, the responsible team identifies the energy sources, the necessary operation, and the possibility of performing it while the power is off. They review the installation data and protective devices, including the risks involved in the preliminary work. The organization schedules the shutdown and defines who will carry out each phase according to their skills and authorization.
In this example, the primary decision is to organize the work to avoid exposure during the intervention. Operations that may still present a risk have specific safety measures in place. Afterward, it is verified that the facility is left in the required working condition, and the restoration of power is controlled. Purchasing personal protective equipment without reviewing this sequence would have left essential process decisions unresolved.
Competition, procedures and changes
The distinction between authorized and qualified workers is an integral part of the organization of electrical work. Procedures must define the task, its limits, the necessary equipment, and the conditions for work stoppage. They must also outline how to proceed when circuit identification does not match the documentation or when an unforeseen defect appears.
Risk information must be kept up-to-date and be understandable to everyone working at the facility. Labels, diagrams, and records are helpful, but they don’t replace verifying actual conditions. A configuration change or expansion can alter the assessment. Change management should involve those familiar with the facility and those who plan its maintenance and operation.
Common mistakes
It is a mistake to think that arc flash only affects high-voltage installations or that it requires touching a conductor. It is also a mistake to confuse “equipment stopped” with the absence of energy and to use an assessment from another installation simply because it appears similar. The potential severity must be evaluated using relevant data, without extrapolating distances or protection performance from a different scenario.
Another mistake is treating personal protective equipment as permission to work on live circuits. The decision regarding the work method precedes the selection of equipment and must comply with applicable requirements. Prevention combines organization, design, maintenance, competence, and protection. No single element can be used to consider a risk under control if it has not been assessed for the specific operation.
