Eaton Corporation plc

06/21/2021 | Press release | Archived content

Grid interconnection safety standards pave the way to a low-carbon future

  • Accelerate the energy transition with electrical safety

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Blog series: For safety's sake

Grid interconnection safety standards pave the way to a low-carbon future

Thomas Domitrovich, P.E., LEED AP, vice president, technical sales, 06/21/2021

The energy transition is well underway

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. 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 footprint, optimized energy usage and advanced resilience - but also quite a few complexities when it comes to 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, I believe it is important to prioritize the safety of any project involving distribute energy resources that operate in parallel with the larger grid to minimize 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 blog post will provide an overview of the Article while exploring:

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

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

Thomas Domitrovich,P.E., LEED AP, vice president, technical sales

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. Typically, 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 important to keep NEC Chapters 1-4 in mind when designing and installing grid interconnected systems. These foundational guidelines provide many important safety requirements for wiring, conductor protection and sizing, temperature considerations, and more. Additionally, you cannot 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. This includes interactive inverters, engine generators, and energy storage equipment that are to be connected in parallel with electric utility power. The most common equipment-level listing for inverters used with distributed energy resources is UL 1741. Finally, these systems should be installed by qualified persons (as defined by Article 100) and 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 and influenced by the Institute of Electrical and Electronics Engineers (IEEE) standards 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, provide information on microgrid controllers.
  • 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 extremely 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 spectrum of industry experts is 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 as to 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 various disconnecting types, requirements, labeling, and more without having to search the entire code.

The bottom line is that 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 major increase of energy storage, renewables and other low-carbon technologies on the horizon, the energy transition is fundamentally transforming 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 states. Delayed adoption is a challenge for businesses and communities that are transforming energy systems to better serve their needs and the environment. As result, some installations use technologies that are not addressed in the locally enforced version of the code.

Today's infrastructure must be able to adapt to change. That means designing buildings to support the energy challenges ahead - whether that be resilience, electrification or sustainability. 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.

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