The term “digital twin” means different things to different people. It also often has different meanings across different industries and applications. In the context of electric utilities, the digital twin is an accurate model of physical generation, transmission, and distribution assets, or customer consumption of power.
Models have always been useful, as they let us imagine how physical entities can and should behave. Before digital computers, we had physical replicas that were models of physical entities. To help ensure that full-scale plants meet their production and performance goals, utilities still build pilot plants to model the behavior of the full-scale plant in a physical environment. However, thanks to advances in computer science and creative programming, digital twins can be used to replicate the physical and operational characteristics of a power generation plant or other utility asset prior to construction and also to help improve operations and maintenance over the lifetime of the physical asset.
As new digital twin models are being created, new ways for humans to interact with digital twins emerge. In this ARC Insight, we will explore different types of digital twins and show use cases related to the design, operation, control and safety system testing, market regulations, operator training, and maintenance and planning of electric utilities.
Digital Twins for Utility System Design
Digital computers allow us to make models or replicas as detailed as we choose, without any physical construction. These models and simulations of real systems can be used from any location and be connected to projects in the design, construction, operations, or maintenance phases of utility activities.
Different types of models can be integrated to form a more realistic simulation environment.
When you want to build a process plant or a reactor based electric generator, you can start with a nuclear or combustion reactor model that connects to the process heat and material balance and then create a P&ID drawing with instruments and controls. When you want to build an electric transmission or distribution system, you can start with a single line distribution network drawing and add feeder schematics, integrate transmission and switchgear equipment, and maybe integrate with geospatial network drawings. When you want to analyze an electrical network, all the components on the network can be modeled to produce a steady-state operating condition or dynamically modeled to understand how such a network would handle failures or upset conditions. Different stakeholders can use digital twin models developed in the design phase collaboratively over the lifecycle of the simulated entity.
Using digital twin models, grid and substation designers can size equipment and predict how this new equipment will act during various operational scenarios. Designers can revisit this again in a few years when new construction and load profiles change the situation and keep track of needed upgrades or maintenance.
Designers of large generating facilities like fossil or nuclear plants have long relied on digital twin technology. All aspects of the design are modeled to create construction drawings from CAD models and specify instruments and controls for protection and plant regulation. Simulations are often used to develop or test control systems; check alarms, alarm messages, and trip settings; restart permissives; and configure graphic displays. Once the protection and controls are developed the control system itself is, in effect, a digital twin that can be connected to the process simulation for use in operator training or engineering analysis. In some cases, the operator training system is integrated to CAD drawings in a game-like environment in which field operators play avatars and console operators run the virtual plant while a trainer sees how these operators interact during startups, upsets, or emergencies.
Digital Twins for Utility Industry Training
Operator training simulators are common in large fossil and nuclear power plants. They can also be used to help wind farm operators better understand various failure modes and restart behavior. Wind turbine error codes are generated when machines are tripped off-line, and operators can understand related maintenance tasks or coordinate with the suppliers’ machine experts to maintain, diagnose, and quickly return the machines operation. In the transmission and distribution area, training grid operators along with grid control staff on a dynamic digital twin replica with realistic scenarios means that, when serious faults occur, grid control center staff will know how to work together as a coordinated team, and which generators and loads could help them avoid outages to maintain a comfortable margin of operational flexibility.
With an accurate dynamic digital twin model of a generating asset, or electric grid transmission & distribution (T&D) system, operators can be trained to handle a wide range of failure conditions they would seldom encounter in real operations. Training on a simulator is the most effective way to train operators. This is because they use identical replicas of the control HMI and the simulation behavior matches the behavior of the real control and protection equipment. Operators should be challenged with scenarios that strengthen their understanding of how to handle unusual and often stressful situations.
In nuclear power plants, the ANSI 3.5 standard specifies that the operator training simulation environment must have a specific accuracy or fidelity of the process modeling and the control room environment.
Grid control rooms can have sophisticated wall displays and a range of additional support applications. In this manner, the operation of the grid does not fall on a single console operator but can be distributed across many individuals acting as a team. Here, the digital twin used for T&D operator training may include geographical information systems (GIS), advanced distributed management systems (ADMS), transmission management systems (TMS), energy management systems (EMS), weather forecasting, load forecasting, and the state of various market prices and participation in wholesale and ancillary services markets. Since grid operators still rely on phone calls to various generation and load entities, the simulation of human behavior is often an important part of simulation sessions.
Digital Twins for Utility System Operation
At the operational level, digital twins often force various data sources and software entities to integrate to provide a single version of the truth that can provide operators with the big picture. Data collection from generators, substations, microgrids, and industrial and building loads can be combined with many other data sources to inform grid operators about the overall situation. This real-time data can be integrated into GIS along with weather and smart meter data. GIS can map hurricane storm surges and using digital twin models to predict outages based on rainfall forecasts. At the distribution level, GIS and other simulations can map to BIM (building information modeling) systems to predict loads in large commercial buildings, university microgrids, or other microgrids.
The utility industry faces many operational challenges as renewable generation increases, fossil generation declines, grid energy storage systems evolve, and new wholesale and ancillary services markets change behavior of generators and grid customers have more opportunities to participate in demand response markets. Digital twin technology that can integrate from generation to consumer is evolving and helping utilities cope with new situations.
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