The 2017 edition of the NEC includes five (5) new Articles, three of which focus on the generation, distribution, and storage of electrical power, areas of considerable interest and activity in the electrical industry. In this brief video I provide an overview of the 5 new NEC Articles in the 2017 NEC, including:
- Article 425 – Fixed Resistance and Electrode Industrial Process Heating Equipment
- Article 691 – Large-Scale Photovoltaic (PV) Electric Supply Stations
- Article 706 – Energy Storage Systems (ESS)
- Article 710 – Stand-Alone Systems
- Article 712 – Direct Current Microgrids
Article 691, Large-Scale Photovoltaic (PV) Electric Supply Stations, covers PV supply stations with a generating capacity of 5,000 kilowatts or more. The systems covered by this article differ from those covered in existing NEC Article 690, in that the power generated by a large-scale PV electric supply station is solely for the purpose of supplying power to an electric utility transmission or distribution system at medium or transmission-level voltages. Such facilities already exist and more are planned. Article 690 is oriented to utility-interactive or stand-alone systems that are used to directly supply a premises wiring system and is not a good fit for PV-generating facilities of this magnitude.
Article 706, Energy Storage Systems, provides requirements covering permanently installed systems that can be stand-alone or interactive with other electric power production sources. Historically, lead-acid batteries—and, more recently, new battery technologies used for energy storage—have been covered in Article 480. However, batteries are not the only form of energy storage devices available today. Flow batteries, capacitors, flywheels, and compressed air are other forms. The article centralizes the requirements for all energy storage technologies, including the current requirements in Article 480, into a single NEC article.
Article 710, Stand-Alone Systems contains requirements power production sources operating in stand-alone mode. This would apply to an off-grid systems having a source such as photovoltaic, wind, hydro, fuel cell, fossil-fuel powered engine generator or other that is not interconnected with an electric utility or other source of electrical power. The new article does not limit the size of these systems, but does allow the source to be sized smaller than the total calculated load as long as it is not smaller than the single largest item of utilization equipment. Other allowances include permission to have a 120 volt source supplying 120/240 volt distribution equipment. Use of this approach requires a special label that warns of the hazard of connecting a multiwire circuit to a single line 120 volt supply.
Article 712, DC Microgrids, covers direct-current power systems where DC sources such as photovoltaic, wind turbines, and fuel cells supply power directly into a distribution system to supply DC utilization equipment such as LED lighting,
communications equipment, computers and servers, variable speed motors, heating/ventilating/air conditioning equipment, and more. Efficiency is gained as the typical DC–AC, and then AC–DC, conversions are eliminated. DC distribution systems of this nature are currently being used in data centers throughout the world, and could in fact be used in any setting where on-site DC generation supply, such as a PV system, is used to supply a distribution system. Coupled with energy storage capability, such systems also provide for a reliable on-site system that is uncoupled from the typical offsite power system and thus not subject to interruptions occurring in the offsite sources.
The new article in Chapter 4, Fixed Resistance and Electrode Industrial Process Heating Equipment provides a set of requirements for specific types of process heating equipment. It borrows on some of the concepts contained in existing NEC Articles 422 on cooking appliances using resistance heating, Article 424 on fixed electric space heating, and Article
427 for pipeline and vessel heating. Rules in Article 425 cover topics such as product certification, working space, control and circuit protection, marking and separate parts covering fixed industrial process resistance-type boilers and fixed industrial process electrode-type boilers respectively.
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