January/February 2021 | Vol. 26 No. 1
by Ronald Farquharson, DNP Users Group, Mount Victoria Consulting, and Grant Gilchrist, DNP Users Group, Tesco Automation
Mr. Farquharson has more than 30 years of experience in transmission and distribution automation technologies and Standards, focusing on data communications, intelligent devices, gateways, synchrophasor measurement, precision time, and equipment- condition monitoring.
Mr. Gilchrist, P. Eng., is a Member of several utility data communications Standards groups, including the IEC working groups for SCADA, substation automation, protocol security, and interoperability.
As the pace of renewable energy deployments continues to grow, the importance of optimizing the interoperability and security of associated measurement and control equipment is also increasing.
Larger deployments of Distributed Energy Resources (DERs) create a greater need for interoperability, increase the size of cybersecurity-related attack surfaces, and expand the probability of overall vulnerabilities. In response, the Distributed Network Protocol (DNP) Users Group, the MESA Standards Alliance (MESA), the Electric Power Research Institute (EPRI), and The Institute of Electrical and Electronics Engineers (IEEE) have developed new Standards solutions and extended existing Standards to address these new concerns.
Role of DNP3 in DER Communications
At the center of recent DER communications developments is the Distributed Network Protocol (DNP3), formally referred to as IEEE Std 1815TM. It is implemented in millions of existing utility devices and used by the vast majority of North America’s utility control centers. Furthermore, IEEE Std 1815 is specified in IEEE Std 1547-2018TM, the IEEE Standard for interconnecting DERs, as one of the protocol options to be used for communicating with DERs. The DNP Users Group (DNP-UG), comprised mostly of expert volunteers from industry, controls the evolution of the Standard, and works with other groups such as EPRI, MESA, the IEEE, and the International Electrotechnical Commission (IEC) to improve its functionality, security, and interoperability. The DNP-UG currently has several active programs in place or underway to maximize interoperability (e.g., the Conformance Certification Program and updated test procedures) and cybersecurity (e.g., DNP Secure Authentication and the next generation Authorization Management Protocol). The DNP-UG also recently completed a profile document for communicating with DERs.
IEEE Std 1815 (DNP3) in IEEE Std 1547-2018
The IEEE 1547-Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric Power Systems Interfaces was updated in 2018 to include essential new requirements for reactive power support, voltage, and frequency “ride-through.” It addresses a notable shift toward optimizing Bulk Power System (BPS) dynamic and transient stability. The IEEE Std 1547-2018 Standard also specifies three communication protocols: DNP3, IEEE Std 2030.5TM and SunSpec ModbusTM.
MESA and EPRI
To maximize interoperability between DERs and utilities, the DNP-UG, MESA, and EPRI collaborated to develop a detailed protocol profile, including a standardized points list. The profile did not change the protocol, but it detailed directions on how to use the protocol for a particular application—in this case, DERs. The document’s purpose is to integrate DERs simply by requiring each device to provide the same data for monitoring and control at the same predictable locations, in the same expected formats, using the same protocol options. The DNP-UG refers to the resulting work as the DNP3 Profile for Communications with DERs (AN2018-001), while the MESA version is called the MESA-DER Specification. Both the DNP-UG and MESA provide access to the documents to their Members.
Introducing the DNP3 DER Profile
With the increasing deployments of DERs on the grid, new and extended communications methods are becoming essential to enable utilities and the public to maximize the operational functionality and financial value of distributed energy and other assets.
The DNP3 DER Profile was based on pioneering industry work by EPRI developing the EPRI Common Functions for Smart Inverters, and the specifications that have made use of it, including; IEC 61850-7-420, IEEE 61850-90-7, IEEE Std 1547-2018, California’s Utility DER Electric Rule 21 Interconnection, and the European ENTSO-E DER interconnection requirements (2016). The profile also references IEEE Std 1815.1TM for mapping between DNP3 and IEC 61850 and previous versions of DNP3 profiles for Advanced Photovoltaic Generation and Storage. Key to the DNP3 DER Profile is its design based on the structured data models for DERs specified in IEC 61850-7-420 Edition 2.0 (under development), which is part of the International Electrotechnical Commission (IEC) 61850 protocol Standards family. This approach brings many benefits for long-term interoperability because it aligns the specification with work on DERs across the world.
The DNP3 DER Profile defines a comprehensive set of point definitions for DER units, inverters, batteries, and meters based on the operational modes described in IEEE Std 1547, the Common Functions for Smart Inverters, and a suite of other functions and modes including schedules and settings groups for islanding and commissioning.
The MESA-DER Specification dictates a subset of the DNP3 DER Profile and includes additional functions of particular interest to Energy Storage Systems.
Work with DNP3 DER Profile
States such as California and Hawaii are continuing to revise their DER regulations and will require independent conformance certification testing of DER communications interfaces. These requirements are critical for optimal interoperability in large systems with equipment from multiple vendors. The DNP-UG has implemented and currently operates a conformance certification program for Standard DNP3 and is working with MESA and other organizations to extend the program to include the MESA-DER Specification and the DNP3 DER Profile. Additional developments include new test specifications, updated XML configuration definitions, and new test tools.
Cyber Security Developments for DER Communications
As stated above, unless strict controls are in place, larger deployments of DER devices tend to expand the power system’s attack surfaces and result in greater overall vulnerability. This vulnerability arises from third-party service providers’ deployment of communications networks, communications with devices owned and controlled by others, and permitted functions such as remote access and control to third parties. These factors combine to raise the importance of cybersecurity requirements for DER systems. The IEEE has recognized this need and has started work on what will become the IEEE Std 1547.3 for securing DERs.
Fortunately, there is an overlap of security requirements for DERs and other parts of the power utility, which enabled the use of previously standardized cybersecurity specifications such as DNP Secure Authentication. The DNP-UG developed that specification as part of a defense-in-depth design. The current version of this Standard is Secure Authentication Version 5 (DNP3-SAv5) and is in IEEE Std 1815-2012. The DNP-UG is now developing SAv6 and a new communication authorization mechanism called Authorization Management Protocol (AMP). Authors may include these technologies in IEEE Std P1547.3.
Defining New Profiles
NEMA and the DNP-UG have identified a potential need for additional interoperability profiles (and associated other documents) based on the example of the DNP3 DER Profile. These new profiles would address other devices, such as distribution feeder reclosers, due to the high numbers of these devices on our power systems. NEMA and the DNP-UG are currently investigating the level of interest in the industry for additional profiles.
The DNP-UG is Member Supported
Several development programs are supportive of, if not crucial to, interoperable and secure communications for DERs. Our dedicated volunteers --many of them experts --continue to provide more than 4,000 hours of volunteer time each year. We develop and make available a wide range of specifications, guides, application notes, and technical bulletins to our Members. The UG also operates our conformance certification program. However, our Members sustain the DNP-UG. If you or your company are not already Members of the DNP-UG, please consider joining us. New memberships are available here. Membership renewals are available here. For assistance and more information, please contact us at firstname.lastname@example.org.
Addressing New Requirements
The growing presence of DER systems and devices on our power systems is driving the need for new or extended mechanisms to optimize interoperability and security for DER communications and enable utilities and the public to maximize the operational functionality and financial value of distributed energy and other assets. Innovative new solutions and improvements to existing ones are on their way. ei