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microgrids, where compatibility with protection will be
considered while developing listing testing procedures. It
builds on the requirements of UL 1741, UL 1741 Supplement
A, and UL 1741 Supplement B, which are all listing standards related to IEEE 1547-2018. Table 4 provides a list of
UL standards that apply to various aspects of system protection with DER interconnections.

Communication and Cybersecurity
Considerations for Protection
Microgrid protection engineers often depend on communication systems for critical protection data and control information. Ethernets used in business and home Internet connections
are vulnerable to frequent interruptions and hacking from
outside sources and are unacceptable for secure microgrid
communications. Protection schemes for microgrids must be
hardened, and cybersecurity policies, plans, and procedures
must be implemented on operational technology.
Advanced communications are required for new protection
strategies. Examples include signaling and dispatch requests,
the coordination of transitions with microgrids and DERs,
phasor measurement units for EPS stability, adaptive loads,
resource logic for predictive and economic schemes, and customized logic for fault detection and mitigation processes.
These communications must be reliable and secured to foil
cyberattacks. There will be instances where one-way communications on dedicated hardwired lines and optical lines will
be necessary to ensure cyberattack immunity. Isolated feedback will be required as well. The self-diagnosis of anomalies
within communications hardware and throughout connected
equipment must be included. A drawback of any communication system is the need for cybersecurity, which adds complexity. Systems must also be able to operate without communications, albeit in some curtailed but safe fashion.
One advanced communication method involves mesh
networks to support the monitoring of individual systems
and the provisioning of inputs to ancillary protection
systems. Mesh networks have been used for microinverters with photovoltaic systems employing ac modules and
microinverters, where each device can communicate with
its neighbor. When adding hundreds or thousands of microinverters to a utility distribution system with protection
devices, the communications and reactions in a mesh network are fast and accurate. The topology of a mesh network
provides monitoring and control redundancy and multiple
pathways for more reliable information exchanges. The
concept supports adaptive protection schemes and detecting and mitigating faults, with each device reporting its
status to a nearby system or to an aggregator that, in turn,
determines where problems are located. Isolating faults is
fundamental to protection. Most devices in a system use the
received information to either block or permit an action to
quickly isolate faults. An aggregator (shown in Figure 2)
can conduct an analysis to determine which devices to trip
while recording an event.
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Conclusions
The increased deployment of DERs, energy storage, and
microgrids is fueling the need for, and the development of,
standards to integrate these technologies into the electric
grid. In the first wave, we see relatively mature standards for
the performance, testing, and certification of grid-following
DERs. With the ability of microgrids and storage to form
grids, a whole new set of standards is now necessary. As
discussed in this article, there is progress toward addressing
communication, control, interoperability, and related cyberconcerns. However, there is a major standards development
challenge ahead to address complex system compatibility and
protection issues.
DER-related standards that are available, under development, and in process have been described in this article. Most
are crafted via a consensus process and require stakeholder
and subject matter expert input and agreement. Multifaceted
microgrid systems bring an added dimension to both the
breadth and the required detail of the standards development
process. There will be an increased need for coordination
and harmonization. The challenges and opportunities are
as vast as the adoption of advanced microgrids and related
technologies that are an important part of the evolution to a
smarter, less centralized grid.

For Further Reading
S. Venkata, M. Reno, W. Bower, S. Manson, J. Reilly, and
G. Sey Jr., " Microgrid protection: Advancing the state of the
art, " Sandia National Lab., Albuquerque, NM, Tech. Rep.
SAND2019-3167, Mar. 2019.
M. Ropp, M. Reno, W. Bower, J. Reilly, and S. S. (Mani)
Venkata, " Secondary networks and protection: Implications for
DER and microgrid interconnection, " Sandia National Lab.,
Albuquerque, NM, Tech. Rep. SAND2020-11209, Oct. 2020.
A. Maitra, J. Simmons, B. Seal, and R. Sarfi, Grid Interactive Microgrid Controllers and the Management of
Aggregated Distributed Energy Resources: Relationship of
Microgrid Controller with DERMS and Utility DMS. Palo
Alto, CA: EPRI, 2015.
W. Bower et al., " The advanced microgrid-Integration
and interoperability, " Sandia National Lab., Albuquerque,
NM, Tech Rep. SAND2014-1535, Feb. 2014.
" Office of Electricity Delivery and Energy Reliability
and National Energy Technology Laboratory, Microgrid Research, Development, and System Design, " U.S. Dept. of
Energy, Washington, D.C., Funding Opportunity No. DEFOA-0000997, Jan. 31, 2014.

Biographies
Ward Bower is with Ward Bower Innovations, Albuquerque,
New Mexico 87111, USA.
Tom Key is with the Electric Power Research Institute,
Knoxville, Tennessee, 37932, USA.

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