3 challenges¡ªand innovative solutions¡ªwhen powering urban communities
December 08, 2020
Rapid urbanization is on the rise. How does this impact grounding design in dense urban settings?
In case you didn¡¯t know it, urbanization is on the rise. In 1950, approximately 751 million people around the world lived in an urban setting. By 2018, this number had grown to 4.2 billion. And a 2018 United Nations data set found that overall population growth and the shift from rural to urban living could push this number to 6.7 billion by 2050. That¡¯s more than two-thirds of the world¡¯s population living in cities!
As the populations of these urban centers grow, so too must the capacity of the critical infrastructure that powers them. Power system grounding¡ªthe interconnected system that disseminates electrical currents into the earth to keep voltage levels at a safe level¡ªis one of the areas seeing mounting pressure for innovative design solutions when standard design is not an option.
Let¡¯s look at a few examples that highlight three key challenges facing urban grounding design, and how our team¡¯s problem-solving ability led us to think outside the (substation) box to help our clients adjust to the trend of rapid urbanization.
As the populations of these urban centers grow, so too must the capacity of the critical infrastructure that powers them.
1. Going in: Adding critical capacity to a busy commuter railroad
When it comes to adding capacity, we often associate it with growth. But what happens when the physical space surrounding the facility limits any physical expansion of the facility¡¯s footprint?
Global urbanization means that infrastructure once built away from densely populated areas is now surrounded by bustling communities. When decommissioning, moving, and rebuilding is not a feasible option, owner companies around the world are being faced with the same challenge: How do we increase capacity and improve operations to meet today¡¯s industry standards without encroaching on the communities that now surround these once remote facilities??
A few years ago, our Â鶹´«Ã½ team was brought on as the lead design firm for a large rail modernization project. The goal? To add critical capacity to a busy commuter railroad. To accommodate the expansion of the railway, upgrades were required at several existing traction power substations¡ªthe systems responsible for providing electrical power to the railcars. In the context of substation grounding, standard design typically involves moving the perimeter grounding conductor outside the substation fence. We knew right away that for this substation, standard design was not an option. Built many decades before and now directly bordering residential properties, our design would require some out-of-the-box thinking. So instead of designing a grounding conductor outside of the substation, we reimagined what things could look like inside the substation box.
By proposing to move the perimeter grounding conductor to the most controlled environment possible¡ªinside the substation fence¡ªit provided the largest safety margin for nearby residents. The team knew it also required additional safety measures for those working in and around the substation, including a ¡°no-touch zone¡±. The ¡°no-touch zone¡± highlights where personnel are not to handle grounded equipment and was paved with asphalt¡ªwhich performs three times better than any insulating gravel and creates a zone distinction for workers.
This innovative design refurbished an almost 50-year-old substation site to meet today¡¯s commuter needs and industry standards without encroaching on the adjacent community¡ªa true display of our commitment to safety and designing with community in mind.?
To accommodate the expansion a railway, upgrades were required at several existing traction power substations¡ªthe systems responsible for providing electrical power to the railcars.
2. Going up: Navigating flood zones in urban settings
Substation grounding design takes on a whole new level of intricacy when the substation is not actually on the ground, but eight feet above it. When a substation existing in a now-identified flood zone requires upgrades to handle the increased load and electricity demand expected with city growth, suitable architectural controls are a must.
On a recent substation upgrade, our team was brought on to solve this challenge in a dense downtown area. To address the flood-level risks, we mounted substation equipment on eight-foot platforms and constructed the fence with fiber-cement panels. To evaluate step and touch voltage performance levels in areas surrounding the substation, we developed specialized models to account for the intricate design of the substation fence details. This included such things as the base foundation and the above-ground steel supports, which accounted for the metallic rivets used to fasten the panels.
Ultimately, our work led our client to a substation design that was not only safe for residents but safe from future flooding events.?
Ultimately, we encourage every design solution to start with one question: What can be done to best protect both workers and the public?
3. Going under: Crossing distribution feeder cable under a river
Urbanization often results in adding new residential communities on the outskirts of a city. In most cases, delivering electricity is rather straightforward. But what about when the expanding community is on the other side of a beloved community river valley? In this instance, our teams were hired to design a route for distribution lines for five electrical distribution feeders across a 100+ meter-wide river without eliminating the aesthetic views offered by the river valley. The result? Horizontal directional drilling a steel pipe casing underneath the river.
The project required the Â鶹´«Ã½ of our multidisciplinary team¡ªincluding environmental, geotechnical, electrical, and civil engineers¡ªto design a borehole for the 36-inch steel pipe casing, distribution system duct design, cable ampacity, and inductive coordination with a nearby transmission line right-of-way that included a 500-kilovolt transmission line.
After the project was complete, residents could still enjoy the river valley without seeing cables crossing the beautiful landscape.
Our teams were hired to design a route for distribution lines for five electrical distribution feeders across a 100+ meter-wide river without eliminating the aesthetic views offered by the river valley.
Evolving challenges, evolving solutions
Urbanization has benefited and challenged our society for generations. It will continue to do so in the future. The electrical utility industry continues to face the demand for increasing capacity on existing infrastructure. This challenge requires effective strategies for urban developers when utilizing real estate within and around high-voltage transmission lines. In addition to the above examples, other innovations include improved analysis methods. This gives us the ability to model and calculate scenarios in advance of accepting designs to ensure that achieving an appropriate degree of step and touch voltage performance is possible. This is recommended for substation retrofit projects as well as new substation installations. Electromagnetic interference and other factors also need to be considered.
Ultimately, we encourage every design solution to start with one question: What can be done to best protect both workers and the public?