The Introduction and application of PVC shield wire
PVC shield wire is an electrical wire of one or more insulated conductors enclosed by a common conductive layer. The shield may be composed of braided strands of copper (or other metal, such as aluminium), a non-braided spiral winding of copper tape, or a layer of conducting polymer. Usually this shield is covered with a jacket. The shield acts as a Faraday cage to reduce electrical noise from affecting the signals, and to reduce electromagnetic radiation that may interfere with other devices. (For more, see electromagnetic interference). The shield minimizes capacitively coupled noise from other electrical sources. The shield must be applied across wire splices.
The best way to PVC shield wire for screening is to ground the shield at both ends of the wire. Traditionally there existed a rule of thumb to ground the shield at one end only to avoid ground loops. Best practice is to ground at both ends, but there is a possibility of ground loops. In airplanes, special wire is used with both an outer shield to protect against lightning and an inner shield grounded at one end to eliminate hum from the 400 Hz power system
The use of PVC shield wire in security systems provides some protection from power frequency and radio frequency interference, reducing the number of false alarms being generated. The best practice is to keep data or signal wire physically separated by at least 3 inches (75mm) from 'heavy' power circuits which are in parallel.