High Voltage Wire and Cable: What you need to know before you buy
Posted Jul 29 2012 11:04am
High Voltage (HV) wire (also referred as leadwire) and cable are used in a variety of applications such as, ignition systems, instruments, AC and DC power transmission in just about every industry.
The wire and cable construction and material are determined by three main factors:
• Voltage- To determine the thickness of the insulation• Current capacity- To determine the cross-section size of the conductor(s)• Environment- Temperature, chemical, UV exposure and mechanical impact to determine the cable construction and material of the outer jacket. High voltage wire has two factors which require special attention. The first is the type of insulation needed to prevent arcs to nearby components, wiring or people. The other is the insulation diameter necessary to reduce corona loss. Reduction of corona is important because a common high voltage problem for insulation is damage to the insulation caused by corona discharge resulting in pinholes. With all high voltage applications, it is important that the insulation of the cable not deteriorate due to the high voltage stress.
Popular insulation materials for hookup type wire are polyethylene, PTFE, FEP, PFA, and silicone. Insulation such as PTFE is less bulky than silicone and is preferred where smaller sizes are required. If a flexible wire is required, PTFE is not a good choice. Silicone insulation is a common choice for high voltage applications especially when co-extruded.
Silicone insulated wire is an extremely flexible wire, even at extreme temperatures, excellent electrical properties and is resistant to most chemicals and moisture to name a few.Why co-extrusion?Corona resistant wire (HVCR) is typically constructed with a conductor surrounded by a semiconducting sheath, which is then surrounded by the insulation. The semiconducting sheath effectively increases the diameter of the wire, reducing the tendency for corona discharge.
Co-extruded wire and cable are common for many high voltage applications for it's ability to effectively reduce corona. Co-extruded wire is the same construction with the semi-conductive layer and outer jacket are extruded simultaneously. The co-extrusion process prevents air and gaps between the conductor and insulating layers thus reducing if not eliminating corona.Custom wire and cable manufacturers can assist you with material choices and cable construction based on your high voltage requirements. Having the right cable from the start will save time and money down the line.