Language of the Grid – The Need for Field Communication
- Aug 23, 2018 11:30 pm GMT
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Our steady progress as humans is a result of our ability to communicate with one another speaking human languages, working together to dream, build, learn, and continuously advance, providing more value together than individually. This ability allows us to “interoperate” as a society with rules, governance, and structure, providing opportunities for each individual to focus their energy on a few things rather than the things you need just for survival. The Internet of Things (IoT) applies this same concept to machines, using protocols, machine languages, and syntax for them to communicate with one another, providing rules and governance, and creating a machine society that interoperates and creates more value together than they would individually.
As our electric power system becomes more and more distributed, the need for assets to work together and not as individuals becomes more and more urgent. Assets need to not only be self-aware, but also aware of the surrounding conditions and other actors that can affect the system and their own health. This would be supported in the field by a manager, or controller, that supports a local area (e.g. a feeder or distribution network) and can communicate with all the assets on the system to manage the overall system health using those assets under its control for voltage and frequency regulation, power factor management, and power quality. Fielded assets require a common “language of the grid” to communicate and orderly behave with one another instead of chaotically or even in direct opposition.
Semantic models are like human dictionaries. They contain the vocabulary for machines – verbs, nouns, adjectives. Modern software best practices are built using clearly-defined semantic structures. Legacy industrial control register-based protocols like DNP, Modbus, and OPC lack semantics and a rich vocabulary that makes communication between a variety of different system actors simpler and less prone to error. IEC 61968/70 Common Information Model (CIM) is a utility semantic model that was primarily designed for back office. IEEE 2030.5 is a semantic model designed for Home Area Networks (HAN) that is based on Smart Energy Profile (SEP), which is compatible and based on CIM. IEC 61850 is a semantic model that was originally developed for substation communications, but has evolved to include field devices, including Distributed Energy Resources (DER).
Protocols are transport mechanisms for data between systems like speaking and writing are to human languages. When performing peer-to-peer communications, IoT purists prefer “routed” messages over “broadcasted” messages. Routed messages are directed to individual actors or groups of actors rather than broadcasted messages, which are sent to all actors on the network. With broadcasted messaging, each actor must then sort through the messages to determine which ones they need. One routable messaging option is the publish/subscribe (Pub/Sub) messaging paradigm. Using this form of protocol, an actor can receive messages only when it has subscribed (and was approved) to a particular message type (called a topic). On the publish side, the same rules apply, and actors must be approved to send certain topics. Some Pub/Sub protocols can even guarantee that published messages were actually received by the subscribers. The use of Pub/Sub protocols lends itself to reduced traffic, less message processing requirements for the asset actors, and additional security to prevent “bad actors” from harming the system.
Humans and machines must also use the right words in the proper order to achieve understanding between one another. These rules are called “syntax” and it defines properly structured combinations of words in a language. Although syntax is extremely important, you can use different syntax structures using the same semantic models, and still understand what is being communicated. Semantics ensure that regardless of the syntax or the protocol, that the same meaning and behavior are understood. To ensure proper context in a peer-to-peer actor environment, you must use the same semantics or have a translator that can properly communicate with other semantic models – this is called harmonization. Humans learn as babies the proper words and syntax from parents and family. Later in life we learn more in school and are tested on our use of vocabulary and syntax in language and writing classes. Communication between field assets will also require formalized tests to ensure that message construction is conformant with syntax rules to ensure proper communication with other actors on the system.
Without all three of these elements – semantics, protocols, and syntax – communication is not possible. However, these elements actually do exist for peer-to-peer DER asset communication, and it works.
In 2014, Duke Energy and the Smart Grid Interoperability Panel (now merged with Smart Electric Power Alliance) began work on a distributed field asset communications framework to support the proliferation of DERs on the grid. The result was a new North American Energy Standards Board (NAESB) IoT standard called the Open Field Message Bus or OpenFMB, for short. The standard includes a specifications volume and a reference architecture based on CIM that can be tailored to meet different utilities’ requirements. In 2017, the OpenFMB semantic model was extended to harmonize with the IEC 61850 semantic model, leveraging the exceptional work done there with DER modeling. The OpenFMB framework supports several Pub/Sub protocol options and was demonstrated at SGIP’s annual meeting in 2016 and at Distributech the following year with over 25 companies participating in a real-time demonstration. The demonstrations performed microgrid islanding and reconnect operations flawlessly using a variety of different telecom technologies that included 4G, fiber, ethernet, and wifi. Using adapters or translators, the demonstration also interoperated with a variety of other semantic models and protocols, including DNP and Modbus.
This past Spring, SEPA transitioned the OpenFMB technical working group to the UCA International Users Group (UCAIug) in order create a formal OpenFMB user group to help accelerate adoption. The OpenFMB user group will initially focus on a testing conformance and certification program and continue to recruit members – especially utilities. The user group will expand upon its foundational operational use cases, test in their labs, and work with vendors to implement into their product specifications. Ultimately, the intent is to help utilities implement DERs on their OT systems that enhance grid reliability, lower capex and opex costs, increase security and resilience, and support a cleaner environment. Additionally, the OpenFMB User Group efforts will be to provide marketing outreach to make utility stakeholders aware that there actually is a common “language of the grid” for peer-to-peer communication to mitigate high penetration DER.
Consider this is a “call to action” to utility executives to identify people in your organization to get involved. It is the responsibility of the utility community to address the field communication issue, support efforts like OpenFMB, and provide clear requirements to vendors on field asset communication and capabilities. Take a look at OpenFMB. Work with your technology partners to implement and test in your lab. DER proliferation WILL have a profound impact on your business, and managing thousands or even hundreds of thousands of DERs that all speak different languages and use different protocols will be a complex and expensive ongoing effort. Get started today.