Laurent said:
@all other visitors: please share also your experience here with others, it will help to highlight the risks related to electrical short circuits
Shorts cause many issues, One that I was privy to occurred in a large factory. During the installation of cables onto a cable tray one of the large supply cables suddenly pulled loose from the tray, and jumped approx 5 feet to the side causing a worker to receive a crushing blow to the side of his body, The force was sufficient to break the collarbone and cause additional injuries to the shoulder and arm regions. on investigation the cause turned out to be twofold.
1. A high fault current due to an insulation failure at the end of the cable run (not close to where anyone was working) created a large magnetic field arround the cable causing the cable to act like a solinoid, and move to the side, with sufficient force to cause injuries to the workers in the area.
2. The cable had not been secured sufficiently on original installation, and over many years the clips securing it had degraded and left the cable insecure.
Testing verified that electrical short circuit protection operated correctly, and that the supply had in fact been isolated inside the traditional 0.4 seconds required by our legislation. Subsequent testing and remedial action, also identified most of the tray earthing had failed over the years, and the tray was in very poor overall condition. It was then replaced, the earths renewed and the cables secured.
People often overlook the fact that high currents can cause mechanical forces withing cables, and all cables in the proximity of other cables (especially in Multi-Phase installations) must be physically secured to prevent the mechanical forces from causing sudden movement of the cables in the tray.