An Icebreaking Project in China! State Grid Xinjiang Successfully Completes On-Load Zero Sequence Mutual Impedance Test of 750kV Line

On May 26, State Grid Xinjiang Electric Power Co., Ltd. successfully completed China's first on-load zero sequence mutual impedance test of 750kV line at the site of 750kV Kashgar-Bachu double circuits reinforcement project. It has achieved a major technological breakthrough of on-load test by getting rid of the conventional mode of "full-line blackout testing". Such icebreaking practice improves the accuracy of protective relay setting calculation, avoids power outages and reduces approximately 900MWh of electricity loss, thereby accelerating the construction of a new electric power system in Xinjiang Autonomous Region.

State Grid Xinjiang started a technological breakthrough campaign since 2021 and made all-out efforts on the study of on-load zero sequence mutual impedance test. After two years of hard work, the company firstly completed the tests of 110kV line and 120kV line in Bortala Prefecture and Kizilsu Kirghiz Prefecture respectively in 2023, and quickly rolled out the tests across the autonomous region. A total of 31 sets of parallel lines of 220kV and below have been tested.

Under the technical guidance of the National Electric Power Dispatching and Communication Center and the Northwest Grid Electric Power Dispatching Center, and the leadership of State Grid Xinjiang Electric Power Dispatching and Control Center, the company formed a dedicated workgroup together with Grid State Xinjiang Electric Power Research Institute and other entities. After four years of great efforts, they finally managed to break technological bottlenecks and developed the 750kV zero sequence mutual impedance testing system. Through three rounds of on-site investigation and five rounds of scheme demonstration, the workgroup selected the Kashgar-Bachu double circuits reinforcement project as the test site. The traditional blackout test of the double circuits lasted for 12 hours, causing an electricity loss up to 900MWh, equivalent to the daily consumption of 100,000 households.
The success of the test symbolizes that Xinjiang power grid has achieved full coverage of on-load zero sequence mutual impedance tests for transmission lines of all voltage levels. (Wang Xing, Zhang Xiaojun, Zhang Li, Xie Ping)