Introduction
The arc flash calculator of Cable Pro Web software is explained in this tutorial.
In this video, we explain arc flash and the steps to perform an arc flash study. We will also explain the main user interface and how to use the Arc Flash Calculator of Cable Pro Web software. Finally, we will work on some AC and DC arc flash calculations.
What is arc flash?
An arc flash is an explosive event causing dangerous conditions resulting in serious injury or even death to workers or nearby persons, ignition of flammable materials, and damage to equipment.
The skin is prone to 2nd degree burns for arc flash incident energies greater than 1.2 cal/cm2, which can occur at a typical low voltage switchboard with a bolted fault current of 13 kA and an arc duration of 0.1 s, which makes arc flash hazard analysis a crucial part of safety in workplaces.
Steps to perform an arc flash study
There are 8 main steps to performing an arc flash study
- Collect the electrical system data, protective device data, and switchboard equipment data.
- Determine all the modes of operation of the electrical network to find the worst-case fault currents.
- Calculate the currents for three-phase and single-phase bolted faults. Usually, three-phase faults are the worst-case.
- Calculate the arcing current, which will be lower than the bolted fault current. A lower current means the fault takes longer to clear, which is more dangerous.
- Calculate the arc duration, defined as the time it takes to clear the arcing current.
- Calculate the incident energy, which is the amount of energy a person receives at a certain working distance away from the arc source.
- Calculate the arc flash boundary, the distance from the arc source at which incident energy is calculated to be 1.2 cal/cm2, which is the energy level likely to cause 2nd-degree burns.
- Select PPE based on the calculated incident energy at the working distance. Several guides specify PPE requirements based on the level of incident energy.
Main window explained
Starting with the main window of the arc flash calculator.
The arc flash calculator window is divided into five main sections: arc flash section, fault current section, PPE categories section, label section, and results section.
Select the calculation method from the arc flash section and enter the working distance. Inputs, such as electrode configuration and enclosure spacings, need to be entered as applicable to each calculation method. The typical values pop-up provides a typical electrode and/or enclosure data to help you complete the Arc flash section.
The fault current section requires you to enter system characteristics such as supply voltage, bolted fault current, and other system parameters. The arc duration is based on the upstream protective device clearing time.
The Personal Protective Equipment or PPE categories section allows you to select the applicable PPE Standard or guideline. Different categories of PPE are required according to the calculated incident energy. The NFPA 70E-2024 provides three different categories table for incident energy analysis.
The label section is used to generate arc flash hazard labels. Required templates can be selected from the template drop-down. Labels can be generated, and it is editable in Microsoft Word.
The results of the arc flash calculation are displayed in the results section. Arcing current, incident energy at a working distance, and arc flash boundary are calculated. The calculator automatically calculates the minimum PPE requirement and displays the minimum working distances for all categories. The PPE details tab under the results section shows details of the selected PPE category.
Detailed reports can be generated from the report options. The reports show all of the inputs, arc flash results, and PPE requirements.
Example arc flash calculations
The three (3) worked examples given in the video tutorial are as follows:
- IEEE-1584-2018 (AC) arc flash calculation– based on Example D.1 from Annex D
- DGUV (AC) calculation– based on Table A 5-3 of DGUV 203-077 from Annex 5
- DC calculation (Stoke’s Method)
