IEEE Power & Energy Magazine - May/June 2021 - 84

backup power and load prioritization requirements. Very successful systems that include campus and utility applications
have been operational for up to and exceeding a decade. For
these early systems, available codes and standards consisted
mostly of adapted device-level legacy emergency and standby
power requirements. Grid interconnection and efficient, safe
operating requirements were improvised via programmed
computers, and the protection focus was the microgrids themselves. The larger microgrid installations often required qualified staff trained to monitor and operate the systems.
New mandates for interconnection and operation, typically on individual utility infrastructure and at state levels,
are spurring calls for novel protection schemes. The increase
in microgrid deployments requires a stepped-up evolution of
protection standards that is compatible with the integration
of distribution networks. Microgrid protection is discussed in
" Microgrid Protection: Advancing the State of the Art " (see the
" For Further Reading " section). That report discusses many
aspects of microgrid defense and addresses the complexity of
microgrid systems-related protection-and standards.
Compared to less complicated grid-following technologies used for older solar photovoltaic systems, microgrids
that incorporate grid-forming technologies present a new set
of challenges to grid integration and protection. Device and
control standards are being developed as discussed in this article. Microgrid protection is especially complex in that, when
operating in on-grid modes, compatibility with legacy safety
schemes is needed. When operating off grid in islanded modes,
microgrid protection must stand on its own. In this article, we
explore the status of codes and standards that support protection within microgrids and when interconnected with utility
infrastructures. Objectives for both modes include
✔✔ maintaining power quality and power continuity
✔✔ seamlessly transitioning microgrids onto and off
the grid
✔✔ maintaining microgrid and distribution system protection and safety
✔✔ operating with coordinated and independent dispatching capabilities
✔✔ utilizing continuous, fast, and reliable communication
for dispatching and controls
✔✔ coordinating load controls for all practical applications
✔✔ maintaining safety for components, local systems, and
interoperable connections.
Along with the updated IEEE Standard 1547-2018 specifying interconnection requirements at a reference point of
applicability, which is the location where its interconnection and interoperability performance requirements apply,
there is an increased emphasis on DER grid support functions that include reliability, resilience, power quality, communication, and cybersecurity. Some of the compatibility
requirements that are being implemented, but remain to be
addressed, include
✔✔ the expected behavior during start-ups and black starts
✔✔ responses to an abnormal grid
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✔✔ the ride-through during out-of-specification utility

conditions
✔✔ reaction times to out-of-specification conditions.
Progress toward standards for these interconnection issues
has been good, but more is needed to handle the complexity
of microgrids and control of functions such as transitions and
associated protection. The coordination of standards for DER
delivery and protection is an area that still requires attention
in the standards community. Existing standards, codes, mandates, and regulatory requirements have multiple interdependencies that do not provide fully collaborative and coordinated stipulations. There is a need to develop and understand
all requirements and interdependencies as they relate to each
standard. It is important to understand that each requirement
has some level of direct, combined, or indirect impact on
protection. The indirect impact often includes changes in the
functionality response speed and even the reliability of the
devices covered by the standard.
This article includes tables that indicate the status of many
standards and provide a level of relevancy for each. A familiar
analogy is used in the tables to indicate the standards' relevance.
It employs three familiar categories: foundational, structural, and
building block. The foundational category can be seen as equivalent to the foundation of a building, which includes concrete,
reinforcement components, and compacted soil. The structural
category is equivalent to the steel beams that hold the building
together. The building blocks include many aspects of functionality, such as electrical systems, plumbing, and stairs. This analogy provides the reader with a picture of the interdependencies
that create a functional building. The same picture can be used to
better understand that protection does rely on foundational standards, and that without the structural and building blocks, protection will not work. With an understanding of the purpose of the
tables, this article addresses the standards, codes, product certifications, compatibility requirements, and mandates that are the
most relevant to protection. It includes a combination of legacy
and new standards and codes that are compatible for today's and
future installations.

Evolving Protection and Interoperability
Standards for Microgrids
International and domestic standards and codes already exist
for the protection of most electric power system (EPS) equipment and subsystems. Several of the standards and codes,
such as those of IEEE and the International Electrotechnical
Commission (IEC), are updated according to regularly scheduled cycles, and they are written by volunteers who include
experts from utilities, industry, and other stakeholder organizations. Many standards and codes are regularly updated, while
complementary standards are being developed on accelerated
schedules to try to stay current with the smart grid functionalities and devices in DERs and microgrids.
The U.S. Department of Energy Office of Electricity
Delivery and Energy Reliability has been an important
leader in promoting research and development; demonstration
may/june 2021

IEEE Power & Energy Magazine - May/June 2021

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