ELECTRIC KOREA · EK GUIDE #003
What the overhead lines in Nonhyeon-dong reveal about Seoul’s mixed urban power infrastructure
Gangnam is known for high-rise buildings, expensive real estate, and modern commercial districts. That image can make it seem as though every power cable in the area must already be underground.
Yet on a residential street in Nonhyeon-dong, Gangnam-gu, Seoul, I photographed a very different scene: concrete utility poles, overhead distribution conductors, pole-mounted transformers, service wires, and communication cables running between older low-rise buildings and newer properties.
I have worked in South Korea’s electrical field since 2009. From an electrician’s point of view, these photographs do not show an area without modern infrastructure. They show how an established city continues to use reliable equipment built in different periods while underground conversion proceeds street by street.
The short answer
Utility poles remain in parts of Gangnam because undergrounding an existing street requires excavation, new cable routes and ground equipment, coordination with other buried utilities, traffic control, and substantial funding. It is normally completed in stages—not simply according to nearby land prices.
.png "Overhead distribution lines in Nonhyeon-dong, Gangnam")
Why Hasn’t Every Street Been Converted Underground?
Underground power distribution can improve the streetscape and reduce conflicts among overhead lines, trees, buildings, and roadside activity. The conversion of an existing overhead network, however, is a major civil and electrical project.
A typical project may involve:
- Road and sidewalk excavation
- Underground ducts, cables, manholes, and associated structures
- Ground-mounted transformers and switching equipment
- Coordination with water, gas, sewer, and telecommunications infrastructure
- Traffic restrictions, construction scheduling, and restoration work
- Cost sharing and project prioritization among the responsible organizations
These constraints help explain why a major road may be undergrounded while a nearby residential side street still uses poles. Redeveloped blocks, older buildings, overhead networks, and underground networks can therefore exist within a short walking distance of one another.
A citywide project measured in decades
According to the Seoul Metropolitan Government, Seoul’s undergrounding rate was 62.2% at the end of 2023. The city announced a plan to add 600 km by 2040 and raise the rate to 68%. In other words, even Seoul—the Korean city with the highest reported rate—still has a substantial overhead network.
.png "Pole-mounted distribution transformers in Nonhyeon-dong")
What an Electrician Sees in These Photographs
To a passerby, the cables may look like one tangled group. They do not all perform the same job. A Korean urban utility pole can support medium-voltage distribution conductors, a neutral conductor, transformers, low-voltage lines, service drops, street-lighting circuits, and telecommunications cables.
Higher-voltage distribution conductors are generally installed in the upper part of the pole arrangement, with low-voltage power and communications facilities below. Actual construction varies, however, and equipment must not be identified solely by its apparent height, color, or thickness in a photograph.
The pole-mounted transformers visible here reduce the distribution voltage so electricity can be supplied to nearby customers. Keeping transformers reasonably close to the loads also limits low-voltage conductor length, voltage drop, and losses.
Technical note: 22.9kV-Y does not mean 22.9kV to neutral
South Korea commonly uses a 22.9kV grounded-wye distribution system. The nominal 22.9kV value is measured phase to phase.
22.9kV ÷ √3 ≈ 13.2kV
The phase-to-neutral voltage is therefore approximately 13.2kV. Many single-phase pole-mounted transformers are connected between one phase and the neutral, although the actual connection and secondary arrangement depend on the local network and customer requirements.
.png "Overhead power and communication lines on a Seoul residential street")
How Electricity Reaches Nearby Buildings
Power plant → Transmission network → Substation → 22.9kV distribution line → Distribution transformer → 380/220V supply → Buildings
Small homes and other low-demand properties commonly receive low-voltage electricity after transformation on the local distribution network. Buildings with greater demand may instead receive high-voltage power and operate customer-owned receiving and transformation equipment.
This mixture is another reason the streetscape cannot be understood from land value or building appearance alone. The visible network reflects electrical demand, existing routes, redevelopment history, engineering feasibility, and long-term public investment.
Three Useful Korean Field Terms
Conclusion
The utility poles in Nonhyeon-dong are not evidence that Gangnam has been left behind. They are part of a mixed urban network in which older overhead infrastructure continues to operate alongside underground systems and modern buildings.
For the public, the photographs show why undergrounding takes time. For an electrician, they also show how several voltage levels and communication systems can occupy the same narrow street while performing completely different functions.
The most important point is simple: expensive land does not automatically determine how electricity is distributed. Existing infrastructure, construction conditions, safety, coordination, reliability, and budget all shape what remains above ground and what can be moved below it.
Safety reminder
Overhead conductors can be fatal even when they appear insulated or are difficult to distinguish from other cables. Never approach, touch, measure, or attempt to identify them from the ground. Inspection and work near distribution facilities must be left to the utility and properly qualified personnel.
References
- Seoul Metropolitan Government, Overhead Power Line Undergrounding Plan, November 6, 2024.
- Korea Electric Power Corporation, electricity supply terms and distribution-system materials.
- Applicable Korean electrical safety standards and utility practices.
Electric Korea
Korean Electrical Construction · Field Experience · Safety · Technical Education
Website: electrickorea.co.kr
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