Effect of electrode orientation in arc flash testing

The arc flash hazard calculation method proposed in IEEE 1584 is based on tests with the arcing electrodes in a vertical plane and the calorimeters arranged at 90° to this plane. In this paper the results of tests using the IEEE test set-up with both vertical and horizontal electrodes are given. High-speed videography and incident energy measurements show that the arc flash hazard is much worse with the horizontal orientation. However current-limiting fuses are effective in limiting the incident energy, even in worst-case arcing conditions, provided that the bolted-fault current is high enough to cause them to operate in their current-limiting mode. The incident energy values are shown to depend on the size of the trigger fuse wire used. The effect of phase imbalance is also considered.