During the May Day holiday, electric workers in Suzhou, Jiangsu Province, inspected China's largest 500-kilovolt substation. The inspection covered multiple majors, including operation, maintenance and relay protection. Put into operation in December 2010, the Changshu 500kV substation was a key hub for absorbing clean hydropower from Baihetan. After the inspection, its reliability improved, ensuring power supply for the Yangtze River Delta in summer.