Ensuring grid stability: Pre-dawn testing and maintenance operations at Yongle substation

At 4 am on Aug 25, State Grid Shizuishan Power Supply Company deployed testing personnel to the Yongle 220-kilovolt Substation. Immediately after the Shiyong Line A 58212 bay was energized, they began ultrasonic and ultra-high-frequency (UHF) partial discharge live testing, working through the pre-dawn hours to safeguard the grid and support the daytime maintenance work.

The Shiyong Line is the core transmission channel from Shizuishan Power Plant to the Yongle 220-kV Substation, carrying a major share of the region's power supply. Under the maintenance plan, the Shiyong Line B 58211 bay was scheduled for an outage in the daytime of Aug 25. During the outage, the original dual-circuit supply mode would temporarily switch to single-circuit supply via Shiyong Line A, leaving the grid in a weakened operating state with a thin safety margin. Any hidden defect in the Shiyong Line A equipment that tripped the line would cut off the entire supply channel, seriously affect safe, reliable power supply in the area, and destabilize the regional grid in Shizuishan, Ningxia Hui autonomous region.

To fully eliminate the safety risks of single-circuit operation, keep defective equipment out of service, and ensure the smooth progress of the Shiyong Line B maintenance work that day, the company followed its "front-loaded risk control, zero hidden defects" requirement by moving the key testing procedures to the pre-dawn hours. While the night had not yet faded and the chill lingered, the substation was brightly lit. Braving low temperatures, poor visibility, and overnight fatigue, the testing personnel took up positions quickly, worked in close coordination, strictly followed standardized operating procedures, and carried out on-site safety checks, instrument calibration, and data collection and analysis.

During the operation, the staff closely monitored equipment status and inspected every point. Using both ultrasonic and UHF detection methods, they carried out a comprehensive, no-blind-spot screening of partial discharge hazards in the Shiyong Line A 58212 bay equipment, accurately assessed the equipment's post-energization health, and cross-checked operating parameters one by one to ensure early detection, prompt elimination, and zero residual defects. From the early morning until sunrise, all personnel stayed at their posts and worked continuously, maintaining a rigorous and meticulous approach during the whole process and completing all live testing tasks to a high standard.

After the all-night inspection, the equipment of the Shiyong Line A 58212 bay was confirmed to be in stable operation and in good condition after energization, with no abnormal defects. This successfully eliminated grid operation risks during the single-circuit supply period, laid a solid safety foundation for the Shiyong Line B outage maintenance that day, and safeguarded the stable operation of the regional grid.

This pre-dawn operation fully demonstrated the dedication of the maintenance team — fearless of hardship, ready to take on tough battles, and always ready to shoulder responsibility. Going forward, State Grid Shizuishan Power Supply Company will continue to closely monitor special operating modes and key equipment conditions, anticipate and control safety risks in advance, and carry out every test and every maintenance task with care, ensuring the safe, stable, and reliable operation of the grid in its jurisdiction.