This is the electric cover removed from the main panel in a mobile home park. The burn or arc marks are from high voltage - 240V. At some point, the two legs of the 240 volt conductor came in contact with the metal cover. This was an old, and unsafe, main panel so that was not too surprising. Water had been inside of it for some time. In looking up inside the panel, the 220V wires were bare and in such a position that someone removing, or replacing, the panel cover could have, and obviously did, short the live 240V conductors. This is, in my view, the most dangerous panel I have ever inspected.
Thank you for stopping by.
Steven L. Smith