In the afternoon of October, 17, as the last conducting wire passed through the No.1705 Tower pulley led by the main hauling cable and running board, completing the riveting line operation, the span of ±800kV Lingzhou-Shaoxing UHV DC transmission project over 1000kV Changnan line with no power finished putting the conducting wire at the No.2 Lot in Henan, constructed by Sichuan Electric Power Transmission & Transformation Construction Company. This is the first no-power span of UHV DC line over UHV AC line in China's electric power engineering history. It can serve as a reference and provide technical support for UHV span construction in the future.
This UHV span encountered long distance between towers and complicated geographic situations. The power planned to be cut off from October 14 to 23, starting from the No. 1701 Tower and ending at No.1705 Tower on the ±800kV Lingzhou-Shaoxing UHV DC transmission line. The set-up, stringing and accessory installation had to be completed for the 2045-meter-long conducting wire.
Compared with average span, this UHV span had a bigger conductor cross-section and bigger tension, putting a stricter requirement for safety. To ensure its smooth operation, Sichuan Transmission & Transformation Construction Company attached great important to this task and sent technicians for investigation and examination in advance, studying the external environment for the construction along the wiring area, strengthening identification on hazards for on-site operation, and further improving Wiring Operation Instructions. The company applied the requirement for live work, conducted the span blockout with high standard, and stationed 20 professional technicians on site. It invested much manpower and equipment supplies, tripled than that of normal span.
The project team had several sand table inferences and stress calculations for the wiring to determine the adoption of large hauling equipment whose force is twice as much as the average to finish this task. An airship was also used to string the wire for better efficiency. At the same time, technicians set up safety net for the span covering an area of 1000 square meters in key spanning points, preventing the conducting wire from falling using tower supporting suspension span network. To control wire stringing with bigger section in a safer area, the technical team spared no efforts to ensure the pulling board successfully finished riveting line operation with low tension and low speed. Thus, the conductor quality was ensured, conductor volatility was effectively weakened, and the task could proceed in an orderly manner.
Along with stringing, other line setting and stringing work will be carried out, such as hanging insulator string, crimping wire, installing spacer, and dismantling span safety net, to ensure the completion of the span with no power before 23.
