What Causes Earth (Ground) Loops?
It is generally accepted that an earth loop conducts a current from one piece of equipment to the next, and imposes a voltage across the connection. A good question is where does the current come from, and why doesn’t it trip the safety switch? Contrary to common belief, earth loops are not caused by leakage current or some other mysterious current that flows in the earth lead back to the switchboard. If this were the case, it would have to be coming from an active connection via a leakage path, and this would trip the safety switch instantly. The loop is entirely local, and (again) contrary to some claims, connecting equipment to separate mains outlets will almost certainly make the situation much worse. Current in the local loop is created by the stray magnetic field of transformers in the connected equipment. Traditional (EI) laminated transformers are almost always worse in this respect than toroidal transformers, but all mains frequency transformers are capable of generating a cir
