Yazhong-Nanchang

The Yazhong-Nanchang HVDC project is a major ultra-high voltage direct current (UHVDC) transmission line in China. It spans approximately 1,700 kilometers, connecting Yanyuan County in Sichuan Province to Nanchang City in Jiangxi Province, passing through five provinces in total. The project is part of China's West-East Electricity Transmission initiative, designed to transmit clean energy from the hydro-rich Sichuan Province to the load center of Jiangxi Province in East China.

The transmission line operates at ±800 kV, making it one of the world's most powerful UHVDC links. It has a transmission capacity of 8,000 MW, which is sufficient to meet the electricity needs of about eight million people in China.

Construction of the Yazhong-Nanchang HVDC project began in 2019, and it was officially commissioned in June 2021. After 168 hours of trial operation, the project was put into full operation on June 26, 2021. The estimated cost of the project was approximately $3.71 billion.

One of the technical innovations in this project is the adoption of asynchronous control technology for the tap changer, which reduces the regulation times and minimizes the risk of on-site accidents. The protection and control system also includes a reactive power control function for the converter station, allowing it to adapt to various operation modes.

The converter valve components, including the equalizing resistor, radiator, and top suspension mechanism, were upgraded and optimized for this project. New packaging processes were developed for the converter valve modules to ensure transportation quality, especially considering the challenging conditions of the Daliang Mountain region, which is 2,550 meters above sea level and in a 9-magnitude earthquake protection zone.

The Yazhong-Nanchang HVDC project provides significant environmental benefits, it reduces coal consumption by approximately 16 million tons and CO2 emissions by about 40 million tons annually. This makes it an important component in China's efforts to integrate more renewable energy sources into its power grid and reduce its carbon footprint.

The project also supports power transmission from the Baihetan hydropower station and promotes the development of wind and solar resources in Western Sichuan. It serves as a key channel for hydro, wind, and solar power transmission in the western and southern Liangshan area.

In terms of technical specifications, the project uses a double-circuit cable to carry direct current. It employs a hierarchical accessing technology for reactive power control at the receiving-end converter station, which is a new mode of operation for such systems.