February 2022 | Vol. 27 No. 2

By Thomas Domitrovich, P.E., LEED AP, Vice President, Technical Sales, Eaton

Today’s infrastructure must be able to adapt to change. That means designing buildings and grids to support the energy challenges ahead, whether resiliency, electrification, or sustainability.

The transition to a more sustainable, low-carbon future is accelerating, and renewables are expected to provide 50 percent of our world’s energy by 2050.¹ This paradigm shift presents the opportunity to adopt a “Buildings-as-a-Grid” approach that transforms buildings from simple energy loads on the grid into strategic assets by incorporating a bi-directional power flow, distributed energy resources, and intelligent control.

Adopting this approach can provide many benefits, including reduced carbon footprints, optimized energy use, and advanced resilience,but also quite a few complexities in electrical safety. For one, it is far more complex for utilities to balance the grid as more distributed generation and bi-directional energy systems come online. With this in mind, it is crucial to prioritize the safety of any project involving distributed energy resources that operate in parallel with the larger grid to minimize the potential impact on utility systems.

The National Electric Code^® (NEC) Article 705 is a great place to start because it was created to address the challenges of a modern, dynamic energy ecosystem. This text will provide an overview of Article 705 while exploring:

• Its ongoing evolution
• Other critical electric codes for safe grid interconnection
• Why safe grid interconnection is essential for a low-carbon future

Electric Codes Guide Safe Grid Interconnection

The title of NEC Article 705—Interconnected Electric Power Production Sources—says it all. This code addresses how to connect additional power production sources to the existing premises’ wiring system to operate in parallel with the primary source of electricity. The primary source is the electric utility, while other local sources could include onsite energy storage, solar, wind, fuel cells, or generators.

First, it’s crucial to keep NEC Chapters 1-4 in mind when designing and installing grid interconnected systems. These foundational guidelines provide many essential safety requirements for wiring, conductor protection and sizing, temperature considerations, and more. Additionally, don’t lose sight of NEC Article 230, as many of these installations may connect into (or ahead of) facility service entrance equipment.

Further, equipment installed in grid interconnected systems must be approved for its intended use, including interactive inverters, engine generators, and energy storage equipment connected in parallel with electric utility power. The most common equipment-level listing for inverters used with distributed energy resources is UL 1741. Finally, qualified people should install these systems (as defined by Article 100), and they should be inspected by the local Authority Having Jurisdiction (AHJ).

Imagine this process like a three-legged stool supported by NEC installation requirements, product listings, and AHJ enforcement. Each step is a critical consideration to ensure the entire system operates safely and reliably for years to come.  

The Evolution of NEC Article 705

Article 705 was first introduced in the NEC 1986 to control safety hazards and protect associated electrical equipment when implementing alternative energy sources. Since then, the Article has been updated to keep up with technology. Institute of Electrical and Electronics Engineers (IEEE) standards influence Article 705, including:

• IEEE Std 2030.7-2017, IEEE Standard for the Specification of Microgrid Controllers,
• IEEE Std 2030.8-2018, IEEE Standard for the Testing of Microgrid Controllers,
• and IEEE Std 1547-2018, IEEE Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric Power Systems Interfaces. 

The code panels driving the ongoing development of Article 705 consist of highly experienced power professionals, representing the following classifications

• E – Enforcing Authority
• M – Manufacturer
• U – User
• I/M – Installer Maintainer
• R/T – Applied Research/Testing Laboratory
• UT – Utility
• L – Labor

This broad list of industry experts are constantly refining Article 705 to achieve comprehensive yet user-friendly language. This process helps enhance the code to improve the reliability of utility systems while easing implementation for customers.

One recent refinement of Article 705 involved clarifying details surrounding the point of connection on the line side of the service entrance. This is the point of connection for the output of the grid-paralleled power system to the service entrance conductors on the supply side of the service disconnect. Industry professionals were not clear about the requirements for these conductors, what size they should be, how they should be routed and protected. The code panel simplified the definition during the 2020 cycle, and it’s now clear that the power source output circuit includes all conductors between the power production equipment and the service entrance.

Section 705.20 was also updated to reorganize the various requirements for disconnecting means that were previously located throughout Article 705. This section now serves as a comprehensive reference to help the industry understand different disconnecting types, requirements, labeling, and more without searching the entire code.

Article 705 is evolving alongside the transformational shifts in our industry. Although there is always much debate during code revision cycles, the panel has one goal in mind—keeping people and the electric grid safe.      

Safe Grid Interconnection is Critical for a Low-Carbon Future

With a significant increase in energy storage, renewables, and other low-carbon technologies on the horizon, the energy transition fundamentally alters the way power systems work. Adopting the latest version of the NEC is essential to ensure our world manages this paradigm shift safely.

Although the code is updated every three years, its adoption can vary state by state. Delayed adoption is a challenge for businesses and communities transforming energy systems to serve their needs and the environment better. As a result, some installations use technologies that are not addressed in the locally enforced version of the code.

Using the latest version of NEC requirements will go a long way to help make it safe to put power systems to work in new ways while complimenting the local utility grid. ei

¹https://www.eia.gov/todayinenergy/detail.php?id=49876