Recently, the Xiluodu Hydropower Station, which has been operating safely for 13 years, has completed a key upgrade. With its right bank surface 500 kV switchyard and auxiliary facilities fully put into operation, it has joined the original right bank underground powerhouse switchyard to initiate a "dual switchyard" coordinated operation mode. This acts as a "dual safeguard" for the outbound power transmission system, significantly enhancing the reliability and flexibility of power delivery. It further underscores the role of this strategic national asset as a "stabilizer" and "mainstay" in ensuring energy supply.
Addressing O&M Shortcomings
Resolving the Dilemma of "Shutdown for Maintenance"
The Xiluodu Hydropower Station is a pivotal power source for the "West-to-East Power Transmission" strategy, boasting a total installed capacity of 13.86 GW. Its 18 hydro-generating units are housed deep within the mountain across the left and right bank underground powerhouses. The electricity generated by these units is collected at the underground powerhouse switchyard, transmitted upward via Gas-Insulated Metal-Enclosed Transmission Lines (GIL) installed vertically for nearly 500 m, and then routed to surface overhead lines before finally being delivered to East and South China.
Through long-term operational practice, technicians found obvious defects in the original power transmission mode: the rigid "one-to-one" tie between the GIL lines and the overhead lines. Under this setup, maintenance on a GIL line will result?in zero power flow on the corresponding overhead line. Inversely, overhead line maintenance necessitated the shutdown of the corresponding GIL line, which inherently restricted the power transmission capacity.
To bolster power infrastructure resilience and guarantee continuous, highly efficient, and stable power transmission, CYPC initiated a systematic upgrading of the outbound power transmission framework at the Xiluodu Right Bank Station in 2024. The newly commissioned right bank surface switchyard and its auxiliary facilities operate synergistically with the original underground powerhouse switchyard, providing mutual backup and establishing a robust foundation for clean energy transmission.
Reshaping the Power Transmission Model
Making External Power Dispatch and Regulation More Flexible and Efficient
The core of this upgrade lies?in reshaping the operational model. To be specific, the original underground powerhouse switchyard is retained in service, and a new surface switchyard is constructed externally on the right bank. The two switchyards are connected via GIL, forming a "dual switchyard" coordinated operation mode. By opening and closing 15 switches across 5 groups within the new switchyard, the current is guided to flow along designated routes.
The principle is straightforward, yet the construction of the new switchyard still faced numerous challenges. For instance, to achieve seamless integration between the GIL connecting the two switchyards and the inlet GIL pipeline of the original underground powerhouse switchyard, it was necessary to upgrade the GIL connections and redesign the pipeline layout. To this end, CYPC independently developed and adopted a technology that "partially replaces welded GIL with flanged GIL", enabling domestic and imported pipelines to achieve a "seamless connection". The application of this new technology reduced the original 12-hour dismantling operation to a mere 3 hours. Besides, all GIS (Gas-Insulated Metal-Enclosed Switchgear) equipment was installed within 47 days and passed the 740 kV withstand voltage test in a single attempt, verifying its?excellent insulation performance.
Following the upgrade, the GIL and the outbound overhead lines of the right bank station are decoupled from mutual interference. This effectively meets the power grid's safety requirements for redundancy backup, further enhancing the stability and reliability of the station's power transmission.
Serving Major National Strategies
Fully Demonstrating the Hard-Core Responsibility of the Strategic National Asset
The significance of the "dual switchyard" mode extends beyond the power station itself. It is also a crucial move by China Three Gorges Corporation (CTG) to integrate into the national energy strategy and serve the construction of a new-type power system.
It is understood that the Xiluodu Right Bank Station serves China Southern Power Grid. Notably, this project is also a core component of the "Yongshan 500 kV Power Grid Reinforcement Project" initiated by Yunnan Power Grid Co., Ltd., a subsidiary of China Southern Power Grid. On the basis of integrating the original four 500 kV overhead lines (Xihuan Lines A, B, and C, as well as Ganxi Line A), the newly built surface switchyard adds a fifth overhead line, Ganxi Line B, thereby enhancing the power transmission capacity and supply reliability in the direction of Ganding Substation.
With the rapid expansion of renewable energy installed capacity in Yunnan Province, the power grid's demand for flexible peak shaving has become increasingly urgent. The enhancement of external power transmission corridors enables the Xiluodu Hydropower Station to increase its output during peak consumption periods and flexibly reduce generation when renewable energy output is high. This provides vital regulating capacity for accommodating local volatile power sources such as wind and photovoltaic power, facilitating maximum?utilization of regional clean energy.
The commissioning of the "underground + surface" dual switchyard mode at the Xiluodu Right Bank Station is a powerful testament to the transition of China's hydropower industry from "successful construction" to "excellent operation and optimized management". It not only elevates the station's own operational and management standards but also provides a replicable and scalable systematic solution for similar power stations at home and abroad, contributing "CTG Wisdom" to the high-quality development of China's clean energy.
