Whether installed as a large, outdoor electrical yard or camouflaged behind an attractive building, electrical substations play a critical role in electricity transmission and distribution. As with much infrastructure, however, substation age is trending higher, just as today’s increasingly complicated energy networks are asking more of this equipment than ever. This includes enabling a two-way flow of electricity within distribution systems that was never part of planners’ initial visions.
So, as dollars begin to flow from last year’s massive infrastructure bill, utilities will be looking for substation designs that are smarter, not just newer. But when it comes to substations, what, exactly, does “smart” mean?
Why substations matter
Electric utility substations provide a broad variety of services within the nation’s transmission and distribution systems. They can house equipment to switch generators, circuits and lines into and out of operation, change voltage levels and shift power from alternating current to direct current and back again. They also provide valuable monitoring services to enable distribution system managers to track their networks’ operations.
“I believe the substation is the decision point for grid reliability,” said Keegan Odle, managing director of substations for engineering firm Burns & McDonnell, an architecture, engineering and construction firm and electrical system designer in Kansas City, Mo. “It’s there to deliver as much power to a load as we safely can. If you’re tying in multiple 500-kilovolt [kV] transmission lines, then you’re going to have very large substations. If you have a distribution system substation, you can do that in a much more compressed footprint.”
They generally fall into one of three categories:
Step-up transmission substations receive electricity from nearby generating plants and incorporate large power transformers to boost the voltage for more efficient long-distance transmission. They also might include a bus for distributing power between multiple outgoing lines and a tap to feed electricity back to the generating station for its own power needs.
Step-down transmission substations are sited at the opposite end of a transmission line, connecting it to other transmission networks or to a local distribution system. Power here is reduced to lower voltages and fed onto distribution substations.
Distribution substations are located close to end-users. These are the facilities you might see in a fenced-off pad in an industrial area or housed in an otherwise unassuming, urban, low-rise building. They can even be located underground, where space is especially tight. They reduce voltages even further for power distribution to residential and business customers.
The space required for substations varies greatly. Most designs are air-insulated, and their equipment clearance requirements are based on the voltages they handle. Gas-insulated designs can be significantly more expensive but can still pencil out in tight locations such as dense, urban environments. This equipment doesn’t need open air around it for safe operation, so it can even be enclosed.
“If you’re using an air-insulated substation, you’re bound by the clearance requirements of the voltage,” Odle said, noting that utilities need other approaches when equipment is enclosed. “They might retrofit a building and put a gas-insulated unit inside. The cost goes up quite a bit, but you can put a bigger substation in a small footprint.”
Why smarter is better
Many of today’s substations are 40–50 years old, aging at the same rate as the rest of the nation’s electrical system. A decade ago, a 2012 U.S. Department of Energy report pegged the average age of large power transformers, a key component of larger substations, at 38–40 years old. Yes, they might still be functional at a base level, but they’re not designed for today’s increasingly dynamic grid operations. For example, with rooftop solar panels—along with their connected battery systems—these facilities now must monitor two-way power flow, a burden that will only increase over time. As electric vehicles become more popular, substations with the intelligence to monitor grid conditions during evening charging periods could become critical to ensuring power reliability.
When “smart” or “intelligent” are used to describe electrical systems, the ability to understand and react to data is at the heart of the conversation, and that’s certainly the case with substations. In a truly smart grid, these facilities could become data hubs, receiving data from pole-top transformers, understanding what that data could mean regarding near-real-time grid conditions and feeding that information back to inform system-wide control operations.
For today’s decades-old equipment, “the intelligence was just for what was there,” Odle said.
“We now have all this data coming in, and the older-generation devices just weren’t built for that. We need our substations to be just as intelligent to process that data,” he said.
The heart of substation operations
Relays are at the heart of substation operations and are a key target for upgrading. These are the devices charged with monitoring grid and substation conditions and passing on commands to electric control circuits, including breakers or other controllers. Protective relays are especially important because they detect defective equipment and other negative operating conditions and then initiate switching or other operations to restore safety.
While electromechanical designs have predominated for protective relays, new digital approaches can add communications, monitoring and programmable logic capabilities to a relay’s capabilities. This means they could use information coming in from line and transformer sensors to understand when performance is deteriorating before serious problems occur and pass that data on to the utility’s control center. Odle said replacing electromechanical equipment with newer digital offerings is a good option for affordably boosting substation intelligence.
“Upgrading of the relaying and relays is a big thing, because it allows us to do something with the data,” he said. “That’s probably the cheapest and best upgrade, so we can do something with the real-time data we’re getting.”
Broad adoption of the International Electrotechnical Commission’s IEC 61850 standard for substation automation is aiding adoption of newer digital technologies. The standard is an ethernet-based communications protocol that enables devices within a substation to create their own local area network, like that in an office. This approach helps utilities break away from proprietary networking protocols that could lock them into dependence on a single manufacturer’s products. Now, when a relay or other piece of equipment needs replacing, a new unit can be installed that’s compatible with what’s already in place.
While upgrading relays and other equipment and introducing fiber-based IEC 61850-compliant communications can help extend the life of existing substations, existing units may still need replacing after natural disasters or performance shortfalls. Adding new generation within a distribution grid can force substation construction to accommodate the additional capacity. In these cases, construction methods are evolving alongside equipment advances to speed the process along without compromising safety.
Helical piles are one option substation designers are turning to, especially in congested settings where tight site access makes standard foundation practices difficult or where soil conditions aren’t favorable. They’re similar to a driven pile or caisson, in that they transfer building load to the surrounding soil. But instead of being driven into the earth, they are screwed deeply into the ground. Bearing plates at the top of the piles can then be tied into the rebar before concrete is poured to ensure the load is evenly transferred.
“We now have all this data coming in, and the older-generation devices just weren’t built for that. We need our substations to be just as intelligent to process that data.”
--Keegan Odle, Burns & McDonnell
For even faster and more efficient construction, major electrical manufacturers have developed modular substations that can be delivered to a site in shipping containers or platforms with integral structural bases. Often, these can be turnkey installations, with the manufacturer handling the entire job. Electrical equipment is housed in tamper-proof metal enclosures, with feeders installed underground. These low-profile designs can be an easier sell with local zoning authorities, and because they’re modular, they also can be easily expanded.
Looking beyond substations
Substations are really just nodes in a utility’s larger power-distribution system, so companies need to think beyond new sensors and relays to really take advantage of today’s available monitoring and control technologies. Often, this can involve improvements to the supervisory control and data acquisition (SCADA) networks they depend on to deliver data to substations and from the substations to their control centers, along with upgrades to the management software overseeing grid-wide operations.
SCADA systems are independent, closed networks that feed data from meters, transformers and substations back to utility operations centers. Historically, companies have leased bandwidth from local cellular providers, but that’s proving insufficient as monitoring points are growing exponentially. Increasingly, electric utilities are moving SCADA efforts over to their own private long-term evolution (LTE) networks. LTE is a communications standard used by all major wireless carriers around the globe. Private LTE networks provide utilities the bandwidth they need, with increased cybersecurity. They’re also easily expandable, which will be crucial as utilities seek to make their operations more responsive to demands that can shift with passing clouds or a quick ramp-up in electric vehicle charging.
For Odle, the rapid technology shifts are arriving just in time to meet a range of industry needs, from the rapid deployment of solar and storage to an aging workforce that’s simply not getting the influx of younger labor it requires.
“Frankly, we have to do more with less—the workforce for us is pretty fixed, so how do we get more substations deployed faster with the same amount of people?” he asked, referring to the need for more interconnections, more data collection and analysis and more rapid system-response times. But he’s enthused about this challenge, rather than daunted. “It’s about the most exciting time to be in the substation industry you can have, with the changing of the grid.”