EC&M Tech Talk — Article 250, Part X — Grounding and Bonding in Medium Voltage Systems

In this EC&M Tech Talk, Randy Barnett, NFPA Certified Electrical Safety Compliance Professional discusses the rules found in NEC Art. 250 Grounding and Bonding, Part X Grounding of Systems and Circuits of over 1000 Volts. In the field such systems are often referred to as medium voltage. So, Randy begins by clearing up the confusion with the terminology found in the code and another ANSI standard providing voltage classifications for distribution systems. Electricity produces different characteristics as voltages increase. The construction of electrical cables and equipment is different for medium voltage systems. All of this leads to understanding the different rules for grounding of systems over 1,000 vac and 1,500 vdc.

Next the Tech Talk explains the rules of Part X. These include the relationship of Part X to the other parts of the article. Specific rules covered address:

• Solidly grounded neutral systems 
• Impedance grounded neutral systems 
• Grounding of Service Supplied AC systems 
• Portable and mobile equipment 
• Grounding of equipment 
• Substations, fences, and other metal structures

If you need to apply any code requirements to systems, circuits or equipment operating over 1,000 vac or 1,500 vdc this Tech Talk will supply you information you need for installing these systems. For the experienced installer of medium voltage systems, this Tech Talk is an excellent review of the NEC rules.