Electrode Configuration

The IEEE 1584-2018 model introduced five electrode configurations to improve the accuracy of arc flash calculations compared to the previous model's generic approach. VCB (vertical conductors in a box) represents arc formation between vertical busbars inside an enclosure, directing energy horizontally toward the worker — this is often the worst case. VCBB (vertical conductors terminated in a barrier) models arc formation with a barrier behind the electrodes that reflects energy forward. HCB (horizontal conductors in a box) represents horizontal busbars in switchgear, where the arc tends to be driven upward by magnetic forces. VOA (vertical conductors in open air) and HOA (horizontal conductors in open air) model arc events in open environments without enclosure focusing effects. The electrode configuration significantly affects both the arcing current and the incident energy: a VCBB configuration can produce incident energy 2–3 times higher than an HOA configuration with the same bolted fault current and clearing time because the enclosure concentrates the thermal energy toward the worker's position. Correctly identifying the electrode configuration for each piece of equipment is essential for accurate arc flash labelling.