On April 28, my country's first "AC to DC" power transmission project - the Yangzhou to Zhenjiang ±200 kV DC transmission project (hereinafter referred to as the "Yangzhen DC Project") was officially completed and put into operation. As a key project in the construction of my country's new power system, this project transformed the AC transmission line in operation into a DC transmission line for the first time. On the basis of keeping the voltage unchanged, the transmission capacity was doubled by adding switch cabinets, isolating switches, lightning arresters and other equipment. , providing a "Chinese solution" for the world's power transmission engineering field to solve development problems such as large power demand, high grid saturation, and limited space for new construction.
Jiangsu power grid load and power distribution are uneven. Wind power, photovoltaic and other power sources are concentrated in the area north of the Yangtze River, while electricity demand is concentrated in the south of the Yangtze River. At present, the six cross-river transmission channels responsible for sending electricity from Jiangbei to Jiangnan have become saturated, but it is more difficult to add new cross-river transmission channels. Through the optimization of key equipment such as vacuum circuit breakers and drop-out fuses, improving the transmission capacity of existing channels has become a new way to solve the "cross-river" problem of clean energy.
The Yangzhen DC project starts from Gaoyou City, Yangzhou City, and ends at Dagang New District, Zhenjiang City. The total length of the line is approximately 110 kilometers. State Grid Jiangsu Electric Power Co., Ltd. renovated and upgraded an existing 220 kV transmission channel without changing the main structure of the Yangtze River-crossing transmission tower, and added transformers and other equipment to enhance transmission efficiency.
"Compared with AC transmission, DC transmission at the same voltage level has greater transmission power and smaller power loss. We transformed the original 2-circuit AC line into a 3-circuit DC line, increasing the transmission capacity from about 500,000 kilowatts to 1.2 million kilowatts." Chen Songtao, director of the Planning and Management Department of the Construction Department of State Grid Jiangsu Electric Power Company, said that the "transformation from AC to DC" also has many advantages such as stability, reliability, economic efficiency and so on.
In addition, this project also uses intelligent construction robots on a large scale, which doubles the work efficiency compared to traditional manual methods. At the same time, State Grid Jiangsu Electric Power Company independently developed nine innovative achievements, including symmetrical unipolar DC control and ±200 kV converter transformers.
The successful commissioning of the Yangzhen DC power grid project provides a model for tapping potential and increasing efficiency for similar regional power grids. It is reported that after the completion of the third phase of the project, Yangzhen DC transmission capacity will reach about 3.6 million kilowatts, which is equivalent to nearly half of Nanjing's electricity load in spring and autumn.