Isolated ground

An isolated ground (IG) (or Functional Earth (FE) in European literature) is a ground connection to a local earth electrode from equipment where the main supply uses a different earthing arrangement, one of the common earthing arrangements used with domestic mains supplies. It is distinct from a TT earthing system where the system electrode is also part of the safety earthing and not neutral bonded. In most countries where regulation permits it, TT is preferred for such systems as conventional wiring techniques can be used. Examples where an IG may be required include radio transmitters where it is not desired for RF currents associated with the antenna and its earthing to enter the mains supply wiring, and in reverse, for sensitive apparatus that should be protected from supply borne interference. Great care has to be taken to maintain system safety with such systems, and each case has to be carefully considered.