On August 27, in the Ocean Transmission Engineering Technology Laboratory of China Zhoushan Power Supply Company, China's domestically-produced 535 kV DC cable insulation material successfully passed the type test. This indicates that China's self-produced 535 kV DC cable materials have the conditions to be put into operation, and the national production of 535 kV DC cable production has been realized.
For a long time, China has not had an independent production capacity of 535 kV DC cables, and technology and products mainly rely on imports. In order to promote the localization of ultra-high voltage DC cables, China's submarine cable manufacturers have separately manufactured 535 kV DC cables and put them into production after passing the tests of authoritative institutions.
The Ocean Transmission Engineering Technology Laboratory of State Grid Zhoushan Power Supply Company undertook the test work of this national key scientific research task, and was responsible for the type test of DC cable materials. Before the start of the test, the Ocean Transmission Engineering Technology Laboratory prepares the test technical plan and the cable accessory production plan, and arranges the cable test circuit. During the test, the testers used infrared and optical fiber temperature measurement methods to eliminate the risk of cable heating one by one, gradually applied a high DC voltage of 990 kV to the cable, tested the cable withstand voltage performance, and continuously monitored the cable heating and voltage stability.
The 535 kV DC cable test environment has strict requirements. The temperature in the laboratory should be between 5°C and 35°C, and the humidity should be controlled below 75%. When the cable is continuously pressurized, the temperature of the cable conductor changes within 2°C and the voltage fluctuates within ±3% to meet the operational standards. The scientific research test lasted more than 140 days. With the continuous technical research of the testers, the type test based on the domestic insulation material of the 535 kV DC cable finally succeeded.
The success of the test broke through the technical bottleneck of domestic insulation material production and broke the monopoly of foreign technology and material production of UHV DC cables. In the next stage, the 535kV domestic DC cable will also be used in the Zhangbeirou direct transmission project to help ensure energy supply for the China Winter Olympics.