However, because power plants, transmission lines, and substations require significant time to construct, concerns are mounting over whether power supply networks can be completed on time to match semiconductor manufacturing facility operation schedules. With the establishment of semiconductor industrial complexes in Yongin and the Honam region gaining momentum, experts point out that failure to promptly build power supply infrastructure could lead to production disruptions, necessitating accelerated investments in generation and transmission facilities.

According to the Long-Term Transmission and Substation Equipment Plan (2024–2038) announced by Korea Electric Power Corporation (KEPCO) last year, the total length of transmission lines is projected to reach 25,587 km by 2038—a 1.72-fold increase compared to 2023. This estimate does not yet reflect the mega-project demands of the Yongin and Honam semiconductor complexes. Furthermore, substation construction projects are expected to increase 1.43-fold to 391 units, while substation capacity is set to surge 1.52-fold to 187,560 MVA. Total investments in transmission and distribution networks are estimated at 113 trillion won, with roughly 73 trillion won allocated for transmission and substations, and 40 trillion won for distribution.

The plan also outlines measures to expand infrastructure for stable electricity supply to national high-tech strategic industry special complexes. For the Yongin semiconductor cluster, KEPCO plans to build internal substations and transmission lines connecting the complex to existing grids to reliably supply over 10 GW of power on schedule. For the national complex, a 3GW new power plant will be integrated into the grid alongside external substations and transmission lines, while general complexes will see additional substations and transmission lines built on top of pre-established reinforcement plans.

KEPCO aims to complete preliminary procedures for transmission line construction at the earliest possible date and commence full-scale work.

For the Yongin Semiconductor Cluster, the first-stage agreement was concluded in 2024, focusing on the construction of a 3GW liquefied natural gas (LNG) power plant within the complex, the establishment of the Dong-i and Seo-i substations, and regional grid integration. Under this agreement, approximately 3GW of power is slated for supply starting in 2029.

The second-stage agreement was finalized in August of this year. It includes constructing new lines between the Sincheon substation and the complex, replacing existing cables, and laying new lines between the Seo-i and Dong-i substations to supply roughly 6GW starting in 2033. Discussions for the third-stage agreement to supply approximately 9GW starting in 2036 are expected to take place next year, with KEPCO planning to finalize details after reviewing various alternatives, including future grid reinforcements and technological advancements.

Meanwhile, the Yongin General Industrial Complex led by SK hynix has completed power supply agreements for a combined 9GW across phases 1 and 2. KEPCO completed the construction of lines linking the Dong-Yongin and Shinsanseong substations to the complex in July of this year to supply 3GW, and is pushing to supply an additional 6GW starting in 2031 through new lines connected to the Shiwonsam and Shiwonju substations.

Efforts to supply power to four semiconductor fabs in the Honam region are also shifting into high gear. Plans involve sequentially building at least two 345-kV transmission line routes and two or more 345-kV substations. KEPCO signed a first-stage agreement this August to supply approximately 3GW starting in 2029, which involves building the new Shingwangsan substation and branching off from the Shinjangseong–Shingwangju lines. Preparation for the second-stage agreement is currently underway, with detailed supply timing and methods to be finalized after reviewing expansion options for another 3GW.

Challenges in Grid Construction and Timely Execution

Some experts voice skepticism regarding the feasibility of completing transmission lines on schedule.

A primary obstacle is the substantial time required to build 25,587 km of transmission lines. While long-distance 345-kV overhead transmission networks typically take about nine years for site selection, permitting, design, and construction, short-distance underground networks require around four years. In practice, however, delays often arise due to stalled negotiations with local residents or protracted administrative procedures, which power authorities note can sometimes double the actual construction timeline.

Given that over 70% of 345-kV transmission network projects slated through 2030 have yet to break ground—and that construction alone takes at least three to four years once initiated—skeptics argue that timely power delivery to the Yongin and Honam complexes will be an uphill battle. Another challenge is the need for synchronous construction of power plants, transmission lines, and substations, with completion milestones closely aligned with chip plant operation schedules.

In particular, the Yongin National Complex relies on a 3GW LNG power plant for initial power supply, which requires timely installation of auxiliary infrastructure such as LNG pipelines. Stakeholders emphasize that meticulous schedule management is essential to prevent any misalignment that could cripple industrial complex operations.

In response, KEPCO maintains that the transmission network projects for the Yongin and Honam complexes are largely short-distance underground initiatives with relatively brief line lengths, meaning they can be completed on schedule if preliminary procedures are wrapped up early.

"The transmission lines for the Yongin semiconductor complex are relatively short, and substations are densely located near the capital region. Because existing power grids can also be utilized, timely construction is entirely achievable," a KEPCO official stated. "Similarly, the transmission line construction sections for the Honam complex span only 18 to 20 kilometers, allowing us to supply power as planned."

The official added, "KEPCO is not building these transmission lines alone. Connecting the lines to the factories is part of the businesses' role, and by pursuing these projects jointly with Samsung Electronics and SK hynix, we can execute them more efficiently. Once site selection, permitting, and design phases are cleared early, actual construction can proceed rapidly."

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