In this episode of “EC&M Tech Talk,” Randy Barnett, a journeyman electrician, inspector, author, trainer, and electrical safety expert, reviews requirements for medium-voltage conductors and cable.
Randy covers Art. 315 of the National Electrical Code, which addresses requirements for medium-voltage conductors and cable such as listing requirements, construction, installation, and ampacity requirements. Medium-voltage conductors are those rated from 2,001V up to and including 35,000V.
For demonstration purposes, Randy uses a length of Type MV 90 cable with 2 AWG copper conductor. It is a shielded solid-dielectric conductor rated for 5kV maximum if the application calls for 133% insulation and 8kV if the application calls for 100% insulation. Each of the ratings as well as insulation layers are discussed.
Randy also provides a brief overview of Art. 495 regarding equipment that is more than 1,000VAC and 1,500VDC, nominal. He identifies each of the Parts of the Article. Maintenance of medium-voltage conductors and cable is referenced to the NFPA 70B, Standard for Electrical Equipment Maintenance. Safety (always an important consideration) is especially important with working with DC medium voltages. These cables tend to hold a significant charge. Workers must follow the safety requirements for installing personal protective grounds outlined in NFPA 70E.
