An Electrician isolated the 415v panel and checked the fuses, he found they were in open circuit. The fuses were replaced, and on energizing the circuit, the electrician noticed there were sparks coming from the cable connection on fuse holder. Without isolating the panel the electrician then removed the fuses and using a non insulated 4mm Allen key he attempted to tighten the cable on the live side, during this operation the Allen key touched the lower metal shelf causing a short circuit and electrical explosion.