691 Large-Scale Photovoltaic (PV) Electric Power Production Facility.
Code Change Summary: A new article was added to address large scale PV facilities.
There are unique differences between small scale PV systems and large scale PV facilities that are installed and operated for the sole purpose of providing electric supply to a system operated by a regulated utility for the transfer of electric energy.
In the 2017 NEC®, a new article was created to provide specific rules for large scale PV power production facilities. The scope of the new article makes it clear that the article covers large-scale PV electric power production facilities with a generating capacity of no less than 5000 kW, and not under exclusive control of the electric utility company.
These types of facilities generally have specific design and safety features and are typically maintained by qualified persons who are familiar with the equipment involved.
Section 691.10 is interesting in that it provides relief for large scale PV systems from the required DC arc-fault protection requirements needed for small scale PV systems covered in 690.11 as long as the facility has documented fire mitigation plans to address dc arc-faults.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC® edition of NFPA 70.
2017 Code Language:
691.1 Scope. This article covers the installation of large-scale PV electric power production facilities with a generating capacity of no less than 5000 kW, and not under exclusive utility control.
691.2 Definitions.
Electric Supply Stations. Locations containing the generating stations and substations, including their associated generator, storage battery, transformer, and switchgear areas.
Generating Capacity. The sum of the parallel-connected inverter rated maximum continuous output power at 40°C in kilowatts (kW).
Generating Station. A plant wherein electric energy is produced by conversion from some other form of energy (e.g., chemical, nuclear, solar, wind, mechanical, or hydraulic) by means of suitable apparatus.
691.6 Engineered Design. Documentation of the electrical portion of the engineered design of the electric supply station shall be stamped and provided upon request of the AHJ. Additional stamped independent engineering reports detailing compliance of the design with applicable electrical standards and industry practice shall be provided upon request of the AHJ. The independent engineer shall be a licensed professional electrical engineer retained by the system owner or installer. This documentation shall include details of conformance of the design with Article 690, and any alternative methods to Article 690, or other articles of this Code.