Electrical safety: Incident energy study

by | Jan 30, 2018 | Electrical Safety

Electrical safety: Incident energy study

Incident energy is the amount of thermal energy projected onto a surface at a distance from the source, produced during an electric arc event. The anti-arc dimension is the value assigned to a material to describe its resistance to arcing. This value is expressed in cal/cm2 and clothing must comply with ASTM F1506.

What’s an incident energy study?

INTRODUCTION OF STEPS

An incident energy study is used to specify the category of Personal Protective Equipment (PPE) required to perform a live electrical work or to delimit a safety perimeter during live electrical work. An incident energy study considers all equipment from the company’s transformers up to the 125 kVA. It is carried out in several stages, namely:

  • The equipment surveys must be done accompanied by an experienced electrician
  • the electricity distributor’s letter specifying the level of short circuit current at the main entrance of the plant
  • the single-wire electrical diagram with the incident energy levels
  • the calculations of coordination
  • the equipment duty result
  • the protection components defect list
  • the labeling of equipment with incident energy information required in CSA Z462-2018
  • the final report

THE EQUIPMENT SURVEYS MUST BE DONE ACCOMPANIED BY AN EXPERIENCED ELECTRICIAN

A first visit is organized to meet the equipment. To do this, open the electrical panels and take pictures of the protective equipment (figure 1) and the motor force data sheets, ie:

  • circuit breakers
  • fuse disconnectors
  • switches
  • transformers
  • generators engines
  • etc.

Also, the distance between the electrical panels is taken to estimate the length of the cables. It is essential during the visit that the locator be accompanied by an electrician with good experience in the company to ensure that all equipment is well displayed and to reduce the risk of error due to the configuration of the plant.

Figure 1. The equipment surveys

THE ELECTRICITY DISTRIBUTOR’S LETTER SPECIFIED THE LEVEL OF SHORT CIRCUIT CURRENT AT THE ENTRANCE OF THE PLANT

The facility manager must request a letter to the electricity distributor about the electrical arc study data for the plant. This letter provides the available short-circuit current level at the electrical connection point. This can vary from one factory to another, so it is necessary to have this information to perform the study of incident energy.

THE SINGLE-LINE DIAGRAM WITH THE INCIDENT ENERGY LEVELS

Once the equipment surveys have been completed and the electricity distributor’s letter receipt, it is possible to begin the incident energy study. To do this, single-line electrical diagram is made by software using the IEEE 1584 standard for calculations. Each protective equipment is added according to the voltage rated, current rated, interrupt rating, tripping times, etc. The software also considers the contribution of the driving forces: transformers, generators, motors, etc. This contribution increases the level of incident energy and the level of short circuit on the protective equipment. This simulation therefore represents the estimated energy incident in the company as the most real as possible.

THE CALCULATIONS OF COORDINATION

The incident energy study considers the coordination of the protections where the following parameters are produced in the form of a curve: the tripping time, the nominal current of the protections (thermal and magnetic trip curve), the interrupt capacity (the intensity of the short-circuit current). The coordination makes it possible to check that all the protections react in such a way as to isolate as quickly as possible a short circuit while having the least impact on the rest of the installation. If the coordination of the protections is not adequate, in the event of a short-circuit on a piece of equipment, the equipment that is supposed to protect it may not be triggered and it is the protective equipment upstream of it that would be triggered. That is, a large part of the plant could be down when only one equipment could be isolated.

THE EQUIPMENT DUTY RESULT

The equipment duty result makes it possible to verify that the breaking capacity of the protective equipment is sufficiently high to withstand the contribution of the driving forces during a short circuit. This report makes it possible to check that the breaking capacity of the fuses and circuit breakers are sufficiently high. If this is not the case, the risk of fire and explosion will increase.

THE PROTECTION COMPONENTS DEFECT LIST

The defect list is generated for the company with all the points that have been noted on electrical safety. There may be defects related to the maintenance of the installation or the improper use of protective equipment.

THE LABELING OF EQUIPMENT WITH INCIDENT ENERGY INFORMATION REQUIRED IN CSA Z462-2018

Once the energy level is simulated, it is now possible to make the warning labels. These must contain at least the requirements of CSA Z462-2018, which is the following information:

  • Warning
  • Risk of arc flashes and electric shock PPE mandatory
  • Available incident energy and the corresponding working distance
  • Nominal system voltage;
  • The date of the study and update
  • The coordinates of the company that did the study
  • The project numbers

Every 5 years, the incident energy study is required to update of all equipment the plant. Once the warning labels have been printed, a second visit is made with an experienced electrician to install on the entire plant.

Figure 2. Warning labels

THE FINAL REPORT

Once the warning labels are installed on the equipment, an incident energy report is given to the company including all the sections presented previously.

An incident energy study is used to maintain electrical equipment and inform electricians of the category of PPE to be used during energized work to reduce the risk of fatalities and serious injuries caused by arcing electric. The company Intervention Prévention.inc works in the field of incident energy study and will be happy to help your plant.

Contact our experts for more information!

 

Bibliography

  • IEEE 1584-2002 – IEEE Guide for Performing Arc Flash Hazard Calculations
  • CSA Z462-2018 – Workplace electrical safety
  • CSA Z463-13 – Guide d’entretien des installations électriques
  • NFPA 70E-15 – Standard for electrical safety in the workplace
  • ANSI Z535 – Safety Alerting Standards

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Intervention Prévention Inc.

Intervention Prévention concentrates its operations in the field of work safety, offering specialized services following Standards CSA Z462 – Workplace Electrical Safety, CSA Z460 – Control of Hazardous Energy: Lock-out and Other Methods, and CSA Z432 – Safeguarding of Machinery.

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Saint-Mathieu-de-Beloeil (Québec)
J3G 0M8

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