220-kV transformer upgrade boosts summer power supply

The main transformer expansion at the 220-kV Xizi Substation in Zhuji, a county-level city in Shaoxing, Zhejiang province, was completed and began operating on June 4.

The 220-kV Xizi Substation in Zhuji, a county-level city in Shaoxing, Zhejiang province. [Photo provided to chinadaily.com.cn]

This key project strengthens the power supply for Southwest Shaoxing, helping the grid cope with the upcoming peak in summer demand.

Zhuji, home to over 10,000 sock manufacturers, is known as the "international sock capital". Rapid growth in this industry has driven a steady rise in electricity demand.

State Grid Shaoxing Power Supply Company pushed the expansion forward efficiently, raising the substation's capacity from 480 MVA to 720 MVA to meet local demand.

During construction, the company used a refined approach featuring partitioned isolation, staged outages, and phased restoration. For the first time, it dismantled, isolated, and fully restored 220-kV geographic information system busbars, avoiding the load gaps typical of conventional methods. This kept local factories running and ensured a steady power supply for residents.

Staff members work to ensure a reliable power supply. [Photo provided to chinadaily.com.cn]

Throughout the process, transmission, substation, and distribution teams coordinated to ensure a steady supply of power. They operated a 24‑hour on‑duty system combining three‑dimensional inspection, centralized monitoring, and inspection stations, ensuring both construction safety and grid stability.

To address the risk that single‑supply users might lose power during work on the 110-kV section II busbar, State Grid Shaoxing made a temporary re‑routing plan.

By installing temporary cables to move user lines to a standby bay on the 110-kV section I busbar, it minimized business interruptions.

Since the start of the year, State Grid Shaoxing has completed several major projects, including the 500-kV Guyue Substation and the Xizi substation expansion, adding 1,640 MVA of total capacity. These upgrades will provide stronger, more reliable power for the summer peak season.