lsolation and double insulation
another form of physical control is separating energized portions of electrical equipment from those components that people can contact(isolation).Several means can accomplish this.Conductors can be separated from contact by covering them with nonconductive materials(insulation).Another method is to provide two layers of enclosure for energized components.At least one of the layers must be nonconductive,and the nonconductive layer must separate a user from possible contact with any energized component(double insulation).Most portable power tools(drills,saws,etc.) have internal components that cannot energize any portion of the external surface.
a person who work on electrical distribution lines sometimes stands on a rubber pad rated for the work being done. The pad is a form of isolation.It insulates the worker from other conductors so that current will not pass through the worker's body
other equipment relies on isolation. Line worker's tools have nonconductive handles; aerial baskets and their controls use nonconductive material to connect them to the lifting arm so that current cannot pass through the basket.For cranes,devices are available that prevent current from flowing to the cab and chassis if the boom gets close to or contacts an overhead power line