Abstract: A four-person power line crew was replacing a transformer in a 6-meter-long, 2.1-meter-wide, 2.4-meter-deep underground vault. The transformer was in a bank, with another transformer, at the southwest corner of the vault. Six buses were located along the west wall between those two transformers and three other transformers in a bank at the northwest corner of the vault. Three of the employees were in the vault and a helper was outside. One employee, who was standing in front of the buses, contacted a cable elbow before it was disconnected from the bus and caused an electrical fault. The ensuing electric arc burned him and a second employee, who was standing between the buses and the two-transformer bank, mapping the wiring for the replacement transformer. The first injured employee suffered second- and third-degree burns on his face and neck and the back of his hands. The other injured employee suffered burns on his right ear, elbow, and hand. (The original form did not list the second injured worker on an injury line.)