Physical Science, Measurement and Instrumentation, Management and Education, IEE Proceedings A

The author considers the shock risk to a submerged diver in the vicinity of an exposed live electrode, modelled as a point source of electric current. It is confirmed that divergent monopole field conditions exist in the vicinity of the current source and diver, regardless of the presence or form of the return electrode, provided the latter is sufficiently remote. Nearby return electrodes and large insulating surfaces are shown to increase the shock risk to the diver, assessed as the body current flow under specified conditions, and, unless they are allowed for they will lead to under-estimation of the ´safe distance´. Using the principle of superposition, symmetry and images, it is shown how electrode geometry and surface effects can be quantified, and increased safe distances can be estimated. Channels of limited width and depth are shown to increase shock risk considerably, shock currents for very narrow and shallow channels exceeding by 2-3 orders of magnitude the current calculated on the basis of a divergent monopole field in an infinite unbounded medium.