Are There Any Power Transmission Lines That Are Underground?

Yes, there are many power transmission lines that are underground, especially in densely populated areas. Whether in Helsinki, the United States, or around the world, underground power lines offer distinct benefits and trade-offs. This article will explore the prevalence of underground power lines, their advantages, and the challenges they present.

Underground Power Lines in Helsinki

In Helsinki and other modern cities, low and medium voltage networks are predominantly underground, with high voltage networks remaining above ground. This practice has been in place since the communal electric company started in 1909 for reasons of safety and environmental protection. Even in the 1980s, some overhead wires were still visible, indicating the gradual transition from above-ground to underground systems.

Underground Power Lines in the United States

Across the United States, underground power lines are common, especially in suburban and urban areas. In some regions, the power lines serving individual homes are buried, while higher voltage lines are buried for aesthetic purposes or to avoid damage from falling tree branches. For example, in large cities like New York City, Manhattan has extensive underground utilities for both power and communication. Even the trolleys used to receive power through a slot between the tracks.

Historical Context of Underground Utilities

The transition to underground power and utility lines in the United States can be traced back to the late 19th and early 20th centuries. Notably, the collapse of telephone lines during the blizzard of 1888 accelerated this trend. When electric power was added, it too was kept underground as a precautionary measure. This move was driven by the need for improved safety and the desire to protect these crucial components from adverse weather conditions and physical damage.

Advantages of Underground Power Lines

Safety:
Underground power lines are safer from snow, ice, and accidents, such as vehicles hitting overhead poles. This reduces the risk of outages and potential catastrophic incidents. Aesthetics:
Buried power lines do not mar the visual landscape, improving the overall appearance of urban and suburban environments. Protection from Natural Elements:
Underground cables are less susceptible to damage from high winds, snow, ice storms, and branches touching them. This makes them a preferred choice in areas prone to severe weather. Protection from Wildlife Damage:
Underground power lines are inaccessible to animals, which can cause damage to overhead lines or even lead to power outages.

Disadvantages of Underground Power Lines

Heat Buildup:
The proximity of power cables in an underground environment can lead to heat buildup, which may require thicker insulation and more robust cooling systems. Difficulty in Monitoring:
Underground power lines are harder to monitor and maintain. Issues may go unnoticed until a critical failure occurs, making it more difficult to predict and prevent problems. Cost and Inconvenience of Repair:
Underground cable failures can be challenging and time-consuming to repair. Locating the fault, excavating the affected area, and ensuring the repair is correctly implemented are complex processes that can disrupt traffic and cause significant inconvenience. Complexity of Connections:
Establishing new connections or making modifications to underground power lines requires extensive excavation and ground preparation, which can be costly and disruptive to the local environment.

The High-voltage Story

High-voltage power lines pose unique challenges when buried. These cables are often housed in conduits filled with pressurized oil to help cool the cables and prevent overheating. If a high-voltage underground cable fails, the fault point must be identified and the oil must be frozen to contain the fluid, allowing repair work to proceed. Such scenarios have resulted in significant disruptions, as seen when an underground cable failure in a busy state highway and during a major shopping event like Black Friday caused widespread power outages and repairs that took days to complete.

Overall, while underground power lines offer numerous benefits in terms of safety, aesthetics, and protection from natural elements, the disadvantages, particularly in terms of monitoring and the complexity of repairs, cannot be overlooked. The choice to bury power lines remains a careful balance between modernization and practical considerations.