Photo shows workers from Qinghai Electric Power maintaining a steel pylon at the Kunlun Mountains. [Xinhua/ Zhang Hongxiang]

Started on September 5, the annual inspection on transmission and transformation equipment of dc system of Qinghai-Tibet power grid is drawing to a close recently. About 300 workers have been working on an average altitude of 4500 in order to strengthen the protection of winter electricity in southwest China’s Tibet Autonomous Region.