Once again, digital substation technology is a hot topic of discussion. Between climate change, decarbonization, and renewable energy sources it’s hard to pinpoint the driving force behind the headlines. With an evolving technology as adaptable as this one, it’s no wonder it’s in the news. One faction points out digital substations are more resilient with faster restoration times after a storm hits leaving outages in its wake.
Another group is quick to point out digital substations are more reliable due to their ability to interact with other intelligent elements on the grid. Still other supporters say digital substations are needed to manage large numbers of utility-scale renewable generation. While other enthusiasts say handling the wide variety of distributed energy sources and bidirectional power flows is ample reason for deploying digital substations.
There are so many choices/benefits, it’s hard to say what has focused attention on digital substations. If this was a multiple choice test, the answer would be all of the above. Digital substation technology is a powerful tool for mitigating many concerns needing attention. Utilities are expected to mitigate climate change with its extreme weather, or meet net-zero greenhouse gas emissions goals, or replace fossil-fueled generation with clean energy source while keeping costs down and the grid stable.
Technological Crossroad
Why substations? They are the hub connecting all the elements of the power grid. Why a digital substation; aren’t traditional substations full of digital technology too? Keeping it simple, a digital substation is the intelligent link. It has been described as being a virtual bridge between the digital and physical worlds. It does this using intelligent electronic devices (IEDs) interconnected to an IEC 61850 edition-2 process bus and sophisticated communication systems.
IEDs make it easier to transmit and share data between substation yard devices and control and the protection schemes in near real-time. That data can also be quickly accessed internally or compared with data from other intelligent substations. It makes for better utilization of all assets. It also improves the utility’s flexibility when dealing with external forces impacting the grid such as extreme weather events.
There are also internal forces such as distributed energy resources (DERs) working on the power grid. Digital substations can assist with also. Utility-scale DERs are finding their way on the distribution network along with an enormous amount of power generation from the behind-the-meter (BTM) segment. Wherever the DERs originate, they are a challenge for grid operators trying to control all these different sources, and digital substations offer management tools for operating all these DER power sources together.
Evolving Technology
Today’s distribution network has become a complex and busy place and the technology is up to the tasks. It makes the substation an integral part of both data and power management from the entire power grid, not just a small section. Maybe that helps explain why there is so much interest in applying technology to substations. Are we expecting too much from legacy substations? The short answer is yes. That’s why the next-gen digital substation such an important link. Let’s look a little deeper.
Talking with Steve Kunsman, director of Product Management and Applications, Grid Automation North America, Hitachi Energy provided a better understanding of the complicated issues being addressed by today’s next-gen digital substation technologies. Kunsman said, “Digital substations have evolved significantly over the past few years. They are a key element of the electric power grid and are playing a critical part in integrating new forms of carbon free energy into the system.”
Kunsman explained, “The development of the digital substation is a complete departure from the traditional substation. It is applying digital technology based on interoperability. IEC 61850 edition-2 makes it work along with IEDs, process bus technology, logic controllers, and advanced communication network protocols. It’s all about integrating IEDs and other digital technologies directly into the yard equipment and having them work together. It’s using NCITs (Non-conventional Instrument Transformers) like Rogowski coils and fiber optic sensors to replace wire wound measuring equipment such as current and voltage transformers, but it doesn’t stop in the yard.”
Kunsman continued, “Because of interoperability, these smart elements provide a simplified design, which simplifies construction and commissioning over the old-school methods. One example is the elimination of 70% to 80% of the point-to-point copper control wires by being able to use fiber optic cable in the substation. Replacing copper control wiring with fiber optic cables had a ripple effect throughout the substation starting with cable procurement and ending with smaller station footprint and much smaller control buildings. Nothing stayed the same.”
Kunsman pointed out, “Something as simple as placing IEDs in the yard equipment connected via fiber optic cable directly to microprocessors and controllers streamlined data flow. This speeds up the process and eliminates considerable numbers of control and protection panels in the control building. Each step forward substantially reduced labor hours and with all the time constraints utilities face, saving time is a huge plus for technicians doing maintenance or caught up in storm restoration. It’s a simple matter to switch out damaged modules, plug in the fiber cable and energize the equipment. And don’t forget there are also safety considerations represented by not bringing measurement connections from the high voltages into the control building from the yard.”
Kunsman concluded saying, “Digital substations have also gotten smarter with the integration of Hitachi’s Lumada Asset Performance Management (APM) platform into their design. The APM gives them unique predictive, prescriptive, and prognostic awareness of what is taking place in the substation. When an organization interconnects all of their digital substations together, the operator is presented with a near real-time dynamic view showing the power system apparatus health so they can anticipate equipment failure and make decisions faster. This is particularly important to ensure a reliable and resilient supply of electricity as the industry reduces its carbon footprint.”
Available Tech
The latest studies indicate that digital substation technology is not only being deployed but is expanding. According to the Business Research Company, a research firm, the digital substation market is expected to grow from US$ 6.16 billion in 2021 to US$ 6.85 in 2022 at a CAGR (compound annual growth rate) of 11.9%. The global digital substation market is expected to grow to US$ 10.47 billion in 2026 at a CAGR of 11.19%. The report continues saying the increasing demand for electricity is expected to continue propelling the growth of the digital substation market. Some of the leading players in the industry are Eaton Corp., GE Grid Solutions, Hitachi Energy, Mitsubishi, Schneider Electric, Siemens Energy, and others according to the report.
Indonesian utility PT Perusahaan Listrik Negara (PLN Persero) took delivery of its first 150 kilovolt (kV) digital substation from Hitachi Energy this year. The Sidoarjo digital substation is located in East Java and is based on the latest communication protocols for control, protection, and automation. The use of a process bus communication network enables continuous bidirectional exchange of digital data between primary equipment, protection equipment, the SCADA system, and the regional control center.
Several months ago, Empire Offshore Wind awarded a contract to the consortium of GE Renewable Energy’s Grid Solutions and BOND Civil & Utility Construction for a digital onshore substation. It will connect the 816 MW Empire Wind 1 with the New York power grid. GE’s Grid Solutions will provide the digital substation’s advanced digital monitoring, controls, and software systems. Design work began this year and construction is scheduled to start in 2023.
Growing Pains
Technologies like digital substations are making this an exciting time to be involved with the power delivery industry. In tangible terms the typical digital substation design reduces the substation’s footprint by an estimated 60% while control buildings are about 50% smaller in size. Installation times are reduced around 40% of legacy substations. The costs of ownership are also substantially decreased, and restoration times are improved too, since the design is simple and more efficient.
Operationally, the next-gen digital substation takes asset connectivity to a new level, with artificial intelligence, substation automation, and cloud-computing. This is especially important with the proliferation of renewable technologies hitting the grid including all of DERs coming online BTM. One next-gen substation is an enormous advantage for a utility, but when several of these intelligent hubs work together it’s a new ballgame.
By combining multiple next-gen substations, a utility has the ability to see across the entire system in real-time. It’s a virtual perspective of what is happening on their transmission system and distribution network along with a view of the edge of the grid. It’s happening at such a fast pace it’s really changing the dynamics of the power delivery system. As these devices increase in numbers, the grid experiences unpredictable and intermittent swings in generation and consumption patterns, but utilities have to utilize the technology, or they will be handicapped. The grid has always been a competitive place, but it’s more so today!
