IEEE 1584 Editions Comparison

A comparison between the 2002 and 2018 Editions of the IEEE 1584 methodology for determining Arc Flash Incident Energy and Arc Flash Boundary.

There have been two editions of the IEEE 1584 Guide for Performing Arc-Flash Hazard Calculations to date; 2002 and 2018. In the 16 years between the two editions a huge amount of work was put into increasing the accuracy of the model across its entire range. Although it didn't fundamentally change the methodology, the 2018 edition brought a number of refinements that more accurately reflect the behaviour of an arc and the resulting release of energy.

Some of the more significant changes to IEEE 1584 from the 2002 edition to the current 2018 edition are briefly described here. If you have previously had an Arc Flash study completed according to the 2002 edition, it is worth considering getting your results re-calculated according to the latest edition to ensure you are providing accurate information on site as to the hazard level.

2002 vs 2018 Edition

Area of Change 2002 Edition 2018 Edition
Bus Bar Electrode Configurations (i.e. the arrangement of copper work where an arc might occur) 2 different configurations (both vertical, one in air, one in a box). 5 different configurations, based on extensive testing. It now includes three different variants for electrodes in a box, including horizontal electrodes often found in withdrawable switchgear. Horizontal Conductors in a Box (HCB) is generally a worst-case configuration due to the arc plasma being ejected towards the worker.
Enclosure Sizes No allowance for differences in enclosure size. All calculations based on a “typical” 20-inch x 20-inch enclosure. Enclosure size correction factors included in the equations allow for larger and smaller enclosures to be accounted for. In general, a smaller enclosure focuses the arc energy to a greater degree resulting in higher Incident Energy. Shallow cubicles in low voltage systems are also accounted for.
Variation of Arcing Current Compared the protection clearing time at 100% arcing current to 85% arcing current and selected the more onerous. The 85% factor was fixed. An arcing current variation factor is calculated and applied for the individual study case; provides a more accurate indication of how the unpredictable arc may affect clearance times, particularly on low voltage systems.
125kVA transformers as a lower limit Equipment below 240V need not be considered unless it involves at least one 125kVA (or larger) low-impedance transformer. Transformer lower limit has been removed – low voltage systems within the valid range of the equations should be considered as arcs are possible from 208V and up.
Voltage Range The equations were determined for two voltage levels (above and below 1kV) with a discontinuity at 1kV. Valid for the entire voltage range from 208V to 15kV based on extrapolation and interpolation around three voltage levels.
Validity of the Equations There was a single validity range for short circuit and conductor gap. Short circuit and conductor gap ranges are different for voltages above and below 600V.
Grounding Distinguished between Grounded and Ungrounded/Impedance Grounded systems when calculating Incident Energy due to the unstable nature of the arc when it is formed and when it extinguishes. The new model discounts the erratic beginning and ending of the arc to arrive at a more stable model – there is no difference between grounded and ungrounded in this case.
Model Basis Based on around 300 arc flash tests. Based on more than 2,000 additional arc flash tests.

As a result of these changes to the methodology:

  • Incident Energies may be higher in some situations, particularly if equipment is found to have Horizontal Conductors in a Box (HCB) configuration or the enclosure is smaller than standard.
  • Additional data gathering is required to complete study work – enclosure size, electrode configuration and inclusion of lower voltage systems – than previously considered. To assist with this, the 2018 version includes typical data (such as enclosure size, conductor gap and working distance) for a range of electrical equipment.
  • The arcing current is determined with greater accuracy, meaning that there is greater certainty on protection tripping times.

Medium Voltage Example Comparison

The following example Medium Voltage switchgear scenario has been calculated using both the 2002 methodology and the 2018 methodology.

To illustrate the impact of electrode configuration, the 2018 results have been determined for both Vertical Conductors in a Box (VCB) and Horizontal Conductors in a Box (HCB).

In this simplistic example it is assumed that the clearance time remains the same. In reality the change in arcing current may often lead to a change in protection trip times.

Input data:

Voltage 11kV
Bolted Fault Current 15kA
Electrode Gap 152mm
Working Distance 914.4mm
Enclosure Type (2002) Switchboard
Enclosure Dimensions (HxWxD) (2018) 1143mm x 762mm x 762mm
Grounded/Ungrounded (2002) Grounded
Fault Clearance Time 500ms

Results

Calculated Value 2002 Results (VCB) 2018 Results (VCB) 2018 Results (HCB)
Arcing Current 14.5kA 13.7kA 13.4kA
Incident Energy 9.6 cal/cm2 8.4 cal/cm2 18.7 cal/cm2
Arc Flash Boundary 7.7m 3.1m 4.7m

Observations

  • For Medium Voltage systems the calculated arcing current becomes slightly lower.
  • For the Vertical Conductors in a Box (VCB) configuration there is a small reduction in Incident Energy, whilst for the Horizontal Conductors in a Box (HCB) configuration the Incident Energy almost doubles.
  • For Medium Voltage systems the calculated Arc Flash Boundary has generally reduced compared to 2002.

Low Voltage Example Comparison

The following example Low Voltage switchgear scenario has been calculated using both the 2002 methodology and the 2018 methodology.

To illustrate the impact of electrode configuration, the 2018 results have been determined for both VCB (vertical conductors in a box) and HCB (horizontal conductors in a box).

As above, in this simplistic example it is assumed that the clearance time remains the same.

Input data:

Voltage 0.415kV
Bolted Fault Current 30kA
Electrode Gap 25mm
Working Distance 455mm
Enclosure Type (2002) MCC/Panel
Enclosure Dimensions (HxWxD) (2018) 305mm x 356mm x 229mm
Grounded/Ungrounded (2002) Grounded
Fault Clearance Time 500ms

Results

Calculated Value 2002 Results (VCB) 2018 Results (VCB) 2018 Results (HCB)
Arcing Current 14.6kA 20.5kA 19.9kA
Incident Energy 25.2 cal/cm2 24.9 cal/cm2 49.6 cal/cm2
Arc Flash Boundary 2.9m 3.0m 2.9m

Observations

  • For Low Voltage systems the calculated arcing current has generally increased with the 2018 methodology.
  • For VCB configuration the Incident Energy stays around the same, however for HCB the Incident Energy almost doubles compared with the 2002 result.
  • For Low Voltage systems there is little difference in the calculated Arc Flash Boundary.