The world's largest flexible direct current (DC) transformer by capacity has been installed in the heart of Guangzhou. This unit, rated at 770 megavolt-amperes, was set up for the 'Tianhe Dansia' flexible DC transformer project in the Tianhe district of the city, according to reports from the Southern Power Grid Company's Guangzhou Energy Supply Bureau and state broadcaster CCTV.
According to CCTV, the transformer's capacity is sufficient to simultaneously charge approximately 100,000 electric vehicles. This three-phase, water-cooled transformer is the second major component delivered to the site and is key equipment for the entire project.
Standard 220 kilovolt transformers typically have capacities ranging from 120 to 240 megavolt-amperes and rarely exceed 350, meaning this single unit performs the function of several. The development of this equipment required solving several challenges, including suppressing parasitic magnetic flux, balancing insulation against temperature increases, ensuring low noise levels in dense urban areas, and implementing digital twin-based maintenance.
The project aims to eliminate structural weaknesses in the city's power grid. Most of Guangzhou is served by three supply zones—Wumen, Zengcheng, and Guannan—which had limited mutual support capabilities. Energy transfer between these zones required opening numerous switches and waiting for flow balance restoration, which could be a lengthy process and carried the risk of outages. The flexible DC technology functions as an intelligent gateway system and a bidirectional pump between zones: it can transfer surplus energy to a needy zone in fractions of a second and instantly interrupt flows upon excessive increase.
Since the site is located in one of the most expensive areas of the city, the team decided to place the equipment vertically. The converter station reaches a height of 49 meters, making it the tallest ground-based flexible DC conversion station in China. Upon completion, CCTV reported that it will increase the supply capacity for approximately 350,000 households, and an update from September 28 indicates that it will provide reliable support to central Guangzhou with a capacity of 900 megawatts.
Noise was a particular problem in the residential area. The transformer emits a characteristic hum in the range of 100 to 400 Hz, so engineers developed perforated sound-absorbing panels lining the surrounding walls. When sound waves enter the holes, they resonate and are dampened, reducing the transformer's noise level by a calculated 80%–90%.
CCTV stated that all components, from main parts to auxiliary equipment, were manufactured in China. Over 450 workers operated on the site in shifts during the National Day holidays, and the planned trial commissioning date is at the end of the current year. In the future, a substation, a BeiDou station base, and an energy storage station will be placed at this site, forming part of the planned largest multifunctional complex in the country.