NEC 2020 | 691 | Large-scale PV electric supply stations

Mayfield Code Corner NEC 691

In the latest edition of Mayfield Renewables’ Code Corner, founder and CEO Ryan Mayfield walks us through National Electric Code (NEC) 2020 Article 691 covering Large-Scale PV Electric Supply Stations. Here’s an overview of some key sections.

Scope of NEC 691: This article covers installation of large-scale PV systems with an inverter generating capacity of over 5000 kW and not under the exclusive control of the utility.

Mayfield points out “generating capacity” as a key phrase of the scope. That is “the sum of the inverters’ ac power continuous power output at 40 degrees C.”

There’s an informational note that’s not part of the code that clearly calls out ”that these systems are operated for the sole purpose of providing electric supply to a system operated by a regulated utility.”

Section 691.4 states that access is limited to authorized personnel only, and these systems are not installed on buildings – even if it is over that 5 MW size.

Mayfield calls out Section 691.6 because it is referenced in multiple other sections regarding fire plans, arc fault, etc. The first sentence reads: “Documentation of the electrical portion of the engineered design of the electric supply station shall be stamped and provided upon request of the AHJ.”

“So really this is saying that we need to have an engineered system, and when we get into things like calculating the voltage, doing things like the disconnecting means, it all has to be part of the engineered plan,” Mayfield explains. “691.6 does say that the documentation shall include details of conformance with article 690 as they apply or other articles of the code. So, 690 is going to be a pretty anchor part of the code for even our 691 systems. But really having the electrical engineer stamp as part of that is a is a big key.”

Section 691.9 covers disconnection and isolation means. “The disconnect and isolation means doesn’t have to be integral with the equipment it can be remote and of course it needs to be documented,” Mayfield says.

Section 691.11 covers grounding and bonding of fences in regard to the proximity of substations and exposed conductors. “There may be some requirements there as opposed to just a large-scale farm where you have fences purely to keep people out where the grounding bonding requirements would be different.”

Check out the full video for Mayfield’s overview of 691, and the rest of their Code Corner videos here.

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