It is an old adage that electricity and water don’t mix. You wouldn’t want to be standing in a puddle holding a live wire. Why is this? Because water is generally an excellent conductor of electricity and those electrically charged ions are looking for somewhere to land. A human body is a good place, unfortunately.
Nothing has changed in the physics of this statement – except in the rare case of deionised pure water – since it was first suggested, but there are an increasing number of industrial instances where it has become necessary for electrical cables, connection points and electrically-powered machinery to either be in close proximity to water or, in the case of the offshore oil and gas industry, be totally submerged.
The first and most obvious application of electricity in water is the underwater power cable, a very common piece of equipment in almost every country in the world and similarly in most offshore sectors. The ones associated with power transmission for domestic and industrial uses are normally very large, very long (hundreds of kilometres) and can be rated to carry more than 500kV (kilo-volts).