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ARC FLASH HAZARD ANALYSIS

IEEE 1584-2018 - Guide for Performing Arc-Flash Hazard Calculations NFPA 70E-2024 - Standard for Electrical Safety in the Workplace ⚠️ SAFETY WARNING Arc flash incidents cause severe burns, hearing damage, blast injuries and death. This analysis estimates the incident energy a worker is exposed to and the arc-rated PPE needed. === IEEE 1584-2018 procedure === 1. Intermediate arcing current at 600 V, 2700 V and 14 300 V (Eq 1) 2. Final arcing current: interpolated to the system voltage above 600 V (Eq 16-18) or from Eq 25 at or below 600 V 3. Arcing-current variation correction factor and reduced arcing current (Eq 2) 4. Enclosure size correction factor (Eq 11-15) 5. Incident energy at the working distance for both arcing currents (Eq 3-6, Eq 19-21) 6. Arc-flash boundary for both cases (Eq 7-10, Eq 22-24) 7. The higher incident energy governs; PPE per NFPA 70E-2024 Table 130.5(G) Range of model: 208 V to 15 kV three-phase, 50/60 Hz; bolted fault 500 A to 106 kA (≤600 V) or 200 A to 65 kA (>600 V); gap 6.35 mm to 76.2 mm (≤600 V) or 19.05 mm to 254 mm (>600 V); working distance ≥305 mm; enclosures up to 1244.6 mm.

1. INPUT PARAMETERS

System, equipment and protection data used for the IEEE 1584-2018 calculation.
Parameter Symbol Value Notes
System Voltage Voc 480 V Line-to-line; LV model (≤ 600 V)
Bolted Fault Current Ibf 35 kA Three-phase symmetrical rms
Arc Duration (full I<sub>arc</sub>) T 100 ms Clearing time at the full arcing current
Arc Duration (reduced I<sub>arc</sub>) Tmin 100 ms Clearing time at the reduced arcing current
Electrode Configuration VCB Vertical conductors/electrodes inside a metal box/enclosure
Conductor Gap G 32 mm 1.26 in
Working Distance D 610 mm 24.0 in
Enclosure Height H 508 mm Enclosure opening
Enclosure Width W 508 mm Enclosure opening
Enclosure Depth 508 mm typical box

2. ARCING CURRENT

IEEE 1584-2018 gives the average arcing current at three reference voltages from the bolted fault current, the conductor gap and the electrode configuration (Eq 1, Table 1).

2.1 Intermediate Arcing Current (Eq 1)

Where: • I_bf = 35.000 kA (bolted fault current) • G = 32.0 mm (conductor gap) • k_1 … k_10 = Table 1 coefficients for VCB at 600 V, 2700 V and 14 300 V I_arc,600 = 26,890 A

Formula: $$ I_{arc,V_{oc}} = 10^{\,k_1 + k_2 \lg I_{bf} + k_3 \lg G} \times \left(k_4 I_{bf}^6 + k_5 I_{bf}^5 + k_6 I_{bf}^4 + k_7 I_{bf}^3 + k_8 I_{bf}^2 + k_9 I_{bf} + k_{10}\right) $$

2.2 Final Arcing Current at 480 V (Eq 25)

Where: • V_oc = 0.480 kV • I_arc,600 = 26.890 kA • I_bf = 35.000 kA I_arc = 24,242 A (69.3% of the bolted fault current)

Formula: $$ I_{arc} = \frac{1}{\sqrt{\left(\frac{0.6}{V_{oc}}\right)^2 \left(\frac{1}{I_{arc,600}^2} - \frac{0.6^2 - V_{oc}^2}{0.6^2\, I_{bf}^2}\right)}} $$

3. ARCING-CURRENT VARIATION AND REDUCED ARCING CURRENT (Eq 2)

The arcing current varies about its average; the reduced current can take longer to clear and so can release more energy. Both cases are evaluated and the worse governs. • k_1 … k_7 = Table 2 coefficients for VCB • V_oc = 0.480 kV • VarC_f = 0.2465 • 1 − 0.5 VarC_f = 0.8767 I_arc,min = 21,254 A

Formula: $$ VarC_f = k_1 V_{oc}^6 + k_2 V_{oc}^5 + k_3 V_{oc}^4 + k_4 V_{oc}^3 + k_5 V_{oc}^2 + k_6 V_{oc} + k_7 \qquad I_{arc,min} = I_{arc}\,(1 - 0.5\,VarC_f) $$

4. ENCLOSURE SIZE CORRECTION FACTOR

An enclosure focuses the arc energy towards the opening. IEEE 1584-2018 converts the enclosure to an equivalent size and applies a correction factor (Eq 11-15, Tables 6 and 7).

4.1 Equivalent Enclosure Size and Correction Factor (Eq 14)

Box type: typical (Eq 14) • Equivalent width W_1 = 20.000 in (Eq 11-12, Table 6) • Equivalent height H_1 = 20.000 in • EES = 20.000 in (Eq 13) • b_1, b_2, b_3 = Table 7 coefficients for VCB, typical box CF = 0.9999

Formula: $$ EES = \frac{H_1 + W_1}{2} \qquad CF = b_1 EES^2 + b_2 EES + b_3 $$

5. INCIDENT ENERGY

Incident energy at the working distance from the arcing current, the arc duration, the gap, the bolted fault current and the enclosure correction (Eq 3-6, Tables 3-5).

5.1 Incident Energy at the Working Distance (Eq 3-6)

Eq 6 (systems at or below 600 V), with T in ms, D in mm, currents in kA, E in J/cm². • k_1 … k_13 = Table 3 (600 V) coefficients for VCB • The k_3 term uses the full I_arc,600; the k_13 term uses the arcing current of the case Full arcing current: I_arc = 24,242 A, T = 100 ms → E = 16.918 J/cm² = 4.044 cal/cm² Reduced arcing current: I_arc,min = 21,254 A, T = 100 ms → E = 14.917 J/cm² = 3.565 cal/cm²

Formula: $$ E = \frac{12.552}{50}\,T \times 10^{\,k_1 + k_2 \lg G + \frac{k_3 I_{arc,600}}{k_4 I_{bf}^7 + k_5 I_{bf}^6 + k_6 I_{bf}^5 + k_7 I_{bf}^4 + k_8 I_{bf}^3 + k_9 I_{bf}^2 + k_{10} I_{bf}} + k_{11} \lg I_{bf} + k_{12} \lg D + k_{13} \lg I_{arc} + \lg \frac{1}{CF}} $$

6. ARC-FLASH BOUNDARY (Eq 7-10)

• D = 609.6 mm, k_12 = -1.598 (distance exponent, Table 3) • 1.2 cal/cm² = 5.0208 J/cm² (the "20/T" of Eq 7-10) Full arcing current: AFB = 1,304 mm Reduced arcing current: AFB = 1,205 mm

Formula: $$ AFB = D \left(\frac{5.0208}{E}\right)^{1/k_{12}} \quad\text{(Eq 7-10 solved for the distance at which } E = 1.2\ \text{cal/cm}^2\text{)} $$

7. GOVERNING CASE AND PPE

The full arcing-current case gives the higher incident energy and governs. INCIDENT ENERGY: 4.04 cal/cm² (16.92 J/cm²) at 609.6 mm ARC-FLASH BOUNDARY: 1.30 m (51.3 in) NFPA 70E-2024 Table 130.5(G) — PPE for an incident-energy analysis: Arc-rated clothing and equipment with an arc rating at or above the incident energy; arc-rated face shield with balaclava, or an arc-rated hood Minimum arc rating of the PPE: 4.1 cal/cm² Equivalent PPE category (informational scale only): 2 (8 cal/cm²) Required PPE: • Arc-rated long-sleeve shirt and pants, or arc-rated coverall, rated at or above the incident energy • Arc-rated face shield with balaclava, or arc-rated hood • Arc-rated jacket, parka, rainwear or hard-hat liner as needed • Hard hat • Safety glasses or goggles • Hearing protection • Heavy-duty leather gloves or arc-rated gloves • Leather footwear NFPA 70E does not permit mixing the PPE-category method (Table 130.7(C)(15)) with an incident-energy analysis; the category is shown only as a familiar scale. ⚠️ De-energise where possible. Working on energised equipment can cause severe burns, blast injuries, hearing damage or death.

8. CALCULATION SUMMARY

Final results of the arc-flash hazard analysis:
Parameter Symbol Value Notes
Arcing Current (full) Iarc 24.2 kA 69.3% of bolted fault
Arcing Current (reduced) Iarc,min 21.3 kA VarC_f = 0.2465
Enclosure Correction Factor CF 1 typical
Incident Energy E 4.04 cal/cm² full case at 609.6 mm
Arc Flash Boundary AFB 1.3 kmm 51.3 in / 1.30 m
Minimum PPE Arc Rating 4.1 cal/cm² NFPA 70E Table 130.5(G); equivalent category 2 (8 cal/cm²)

9. STANDARDS AND MODEL NOTES

**Standards:** • IEEE 1584-2018: Guide for Performing Arc-Flash Hazard Calculations (Eq 1-25, Tables 1-8 and 10) • NFPA 70E-2024: Electrical Safety in the Workplace (Article 130, Table 130.5(G)) • ASTM F1506 / IEC 61482: arc-rated protective clothing **Range of the model (IEEE 1584-2018 4.2):** • Voltage 208 V to 15 000 V three-phase (system: 480 V) • Bolted fault current 500 A to 106 kA (system: 35.00 kA) • Conductor gap 6.35 mm to 76.2 mm (system: 32.0 mm) • Working distance ≥ 305 mm; enclosure dimensions up to 1244.6 mm **Model notes for this calculation:** • None **Engineering responsibility:** • Arc durations must come from the protective device's time-current characteristic at each arcing current • Re-assess when the system changes (fault level, protection settings, equipment) • Label equipment per NFPA 70E 130.5(H); review at least every 5 years • 1 cal/cm² = 4.184 J/cm²

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