May 22, 2025
The Hidden Costs: What It Takes to Maintain Underground Substations
A new power transmission project that got underway in Massachusetts at the start of the year will be a game-changer when it is complete. It will increase grid capacity, allow for interconnection with renewable systems, and help the state in its pursuit of decarbonization goals. Best of all, a significant portion of the project will be built underground – including a first of its kind underground substation.
None of this is a massive surprise given the fact that underground transmission is the current trend in our industry. Utilities, municipalities, and consumers all understand the benefits of burying transmission lines underground. But where there is underground transmission, there is also the need for underground substations. And that has implications in a lot of areas. Maintenance is a good example.
Why We Need Them
Despite the challenges of building substations underground, it is not as though we can just get rid of them. Substations are an integral part of the power transmission process. A substation is a facility built to convert high voltage electricity to the lower voltages more suitable for residential homes and businesses. Power comes in via high-voltage transmission lines and is carried back out along their lower voltage counterparts.
For the record, underground substations are not new. They are fairly common in urban areas where space is at a premium. Yet they do present their challenges. That takes us back to the maintenance question. As underground transmission continues to gain traction, maintenance will be a more important concern.
4 Big Challenges
Substation maintenance is a delicate matter, regardless of where substations are located. But when substations are built underground, they present four big challenges for utilities:
1. Access
Building underground substations requires building specialized access points. Between hatches, elevators, and other accommodations, it can be tricky to come up with solutions that allow easy access. And the harder access is on technicians, the more difficult maintenance becomes.
Maintenance can be especially challenging when large equipment needs to be replaced. It requires a level of planning that goes beyond what is necessary for an above ground station.
2. Space Limits
Building underground substations is expensive. Therefore, there is a tendency to minimize the physical footprint in order to save money. This creates a problem for maintenance crews. Space limits can complicate movement. It can make replacing large equipment extremely difficult.
Limited space requires additional planning. It also creates a safety issue. When technicians have less space to work in, the risks they face go up.
3. Environmental Challenges
Aboveground substations are subject to mother nature and the elements. Underground, it is a different matter. Underground substations are subject to environmental challenges, including ventilation, heat dissipation, and flood protection. Dealing with such conditions only creates more maintenance needs.
Environmental conditions can make underground maintenance quite complex. And of course, the best way to avoid major problems is to monitor substations around the clock. But even monitoring becomes more difficult underground.
4. Safety
The top priority for any maintenance activity is technician safety. In an underground substation scenario, enhanced safety protocols are needed to accommodate the unique environment. For example, substation design usually calls for escape root redundancy in the event of an emergency.
Underground We Go
The challenges of maintaining underground substations illustrate why underground transmission projects are so hard to get done. Building underground is time consuming and costly. And yet, underground we go.
It is not a bad thing. But as underground transmission gradually replaces overhead transmission, we need to be prepared for higher costs and more difficult maintenance. It's part and parcel of burying the electric grid under our feet.
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