IEEE 1584–2018 — In Depth Arc Flash Calculations Using Mathcad Express & Etap 19.0 (Extensive Results Comparison)

arc flash hazard test on PPE

Many Arc flash software programs including EasyPower, Etap, SKM, ArcPro perform Arc flash calculations in the back end and give only the final result in the form of tables, report and Arc flash labels. In this way, user will not be able to grasp the idea of manual calculations, but as a Power Systems Engineer or Protection engineer, you must know about the manual calculations, on which the whole arc flash study calculations rely or based upon.

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In this blog, we will limit our discussion only for HV Arc flash calculations which are widely used in High voltage applications. We will perform the hand calculations for Arc flash study as defined in the latest standard of IEEE 1584–2018 and then compare our results with the Arc flash analysis software i.e. Etap for a particular scenario in order to know the incident energy level in both cases.

Particular Scenario or Case:​

Let’s consider a Model One line for 15 kV Switchgear (HV system) with HCB electrode configuration which we have made on the Etap 19.0 version.

arc flash study calculations using mathcad and etap
arc flash study calculations using mathcad and etap

Arc Flash Hazard Calculations in 5 Steps Using IEEE 1584–2018 Latest Standard:

IEEE 1584–2018 has provided a summary of the steps required to apply to this model which are used to determine:

1. Arcing current (Iarc)

2. Arc duration (T) or fault clearing time (Tfault) using the same arcing current determined in “Step no.1”

3. Box Size Correction Factor (CF)

4. Incident energy (I.E)

5. Arc flash boundary (AFB)

1st Step: Calculation for Intermediate Average Arcing Current (Iarc) — MV Switchgear

According to the latest standard of IEEE 1584–2018, we need to first determine the coefficients for our first equation based on the HCB (Horizontal Electrodes in a Cubic Box) configuration and voltage levels. According to the given table, we need to calculate the arcing currents at three different open-circuit voltage (Voc).

The equations are discussed in detail here to obtain the value of arcing currents at different voltages.

2nd Step: Arcing current Variation Factor — Calculation

IEEE 1584–2018 has introduced a new correction factor, which will be used to calculate a second set of arc duration, using the reduced arcing current (Iarc_min). Equation for arcing current variation correction factor is determined here.

3rd Step: Determine the Box Size Correction Factor (CF)

In order to determine the box size correction factor, use the equations provided in section 4.8. of the official document of IEEE 1584–2018.

But, first we need to determine if the enclosure should be classified as “Typical” or “Shallow”.

Shallow Enclosure: Depth less than or equal to 203.2 mm (8 in)

Typical Enclosure: Depth greater than 203.2 mm (8 in)

The effect of depth is only considered if the system voltage is less than 600 V.

Read on to find out how these equations are solved here.

4th Step: Determine the Incident Energy (I.E)

We have already present a general formula which will be used afterwards to calculate the incident energy for 600v, 2700v and 14300v.

The incident energy of each level is calculated step by step in an intuitive manner here.

5th Step: Determine the Arc Flash Boundary (AFB)

The final and last step is to find the arc flash boundary (AFB), IEEE 1584–2018 has provided two intermediate equations i.e. (22) and (23) to determine the intermediate arc-flash boundary values.

The incident energy of each level is calculated step by step in an intuitive manner here.

Let us know if you have any queries regarding this topic and do provide us with your feedback in the comments.

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