The importance of inspection in PAT testing

Leicester Hackspace were exhibiting at the Creat-a-Con: Kids exhibition at DeMontfort University on Saturday 11th Feb 2017, and using various mains powered appliances including an oscilloscope fed with a standard IEC kettle lead. Partway through the day, someone smelled burning and spotted what was described as a mini-volcano with smoke coming out of a hole in the cable outer casing near the mains plug. The photograph here shows the hole, which has now stretched into a split due to us looking inside at the wires:

Further investigation shows that the cable is marked as having 3 X 0.75mm wires, but was fitted with a 13A fuse, so was perhaps not suitable for this fuse rating. There is no end-to-end connection now between the Live and Neutral wires - only the ground lead remains. The 13A fuse has not blown. This link shows that although 0.75mm wires should be limited to a fuse of 6A, there is an exception if the lead is less than 2m long. 

http://www.pat-testing-training.net/articles/fuse-ratings.php

The bottom line is that your mains leads need careful inspection in case they have been damaged, although we have no idea if we would have spotted anything wrong with this cable. It seems amazing that the fuse didn't blow, so perhaps the fault developed between neutral and earth, in which case an ELCB should have tripped. We dont know the electrical arrangements in the building we were exhibiting in. Leicester Hackspace is now going to examine all its mains cables carefully, because had this been unattended, a fire could have resulted.