Shizhou Converter Station Completes Annual Maintenance and Submodule Breakover Thyristor Retrofit

Recently, State Grid Hubei DC Company successfully concluded the 2026 annual maintenance and submodule breakover thyristor retrofit at the ±420 kV Shizhou Converter Station.

A panoramic view of the Shizhou Converter Station. Photo by Liao Lu

The Shizhou Converter Station serves as a critical link between the Southwest and Central China power grids. Since its commissioning, the station’s DC system has transmitted a total of 48.3 billion kWh of electricity, providing a solid foundation for the reliable power supply of Chongqing and Hubei.
The Unit 1 submodule breakover thyristor retrofit began on February 28, with 6,480 submodules upgraded within 45 days. The annual overhaul commenced on April 6. Over the course of eight days, the team completed 18 routine maintenance items, 10 differentiated maintenance items, 11 targeted maintenance items, 7 technical overhauls, 22 defect eliminations, 6 hazard mitigation tasks, and 7 technical supervision items, comprehensively improving the equipment’s operational health.

Operation and maintenance personnel inspect the submodule retrofit process in the valve tower. Photo by Liao Lu

To manage the risks associated with a long construction period and overlapping operations, the company implemented several key measures. For simultaneous work fronts, such as valve tower submodule retrofits and bushing replacements, a strict time-segmented and zone-based operation system was enforced. Safety control during testing was strengthened by using safety fences to isolate test areas from work zones, and dedicated safety supervisors were stationed ahead of all high-voltage tests. Daily control meetings were held to report on safety status and clarify priorities for the following day, ensuring that safety measures were integrated into every step and assigned to specific personnel.

Operation and maintenance personnel conduct ultrasonic live-line detection. Photo by He Xiaowei

The Shizhou Converter Station will continue to leverage digitalization and intelligent inspection equipment to carry out regular hazard elimination and lean maintenance. This ensures the equipment remains in optimal condition for the upcoming summer peak demand period, safeguarding the safe, stable, and efficient operation of the Chongqing-Hubei interconnection backbone.