I work with industrial electrical system and I got a question regarding electrical noise caused by electromagnetic radiation. In an industrial environment, cables carrying an analog signal are shielded and its drain wire is earth grounded at one end of the cable. When electromagnetic radiation hits the cable, the induced current drains to the earth via the drain wire. Does the induced current in the shield prefer to travel back to earth? Would the shield of the cable still be effective at blocking the radiation if the drain wire was connected to a really big piece of metal that is not earth grounded?