Influence of closure law of wicket gate on successive load rejection condition
CHU Shanpeng，ZHANG Jian，CHEN Sheng，YU Xiaodong
1. Zhejiang Design Institute of Water Conservancy and Hydroelectric Power, Hangzhou, Zhejiang 310002, China; 2. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, China
Focusing on pumpedstorage power stations with layout of two units per penstock, a few closure laws of wicket gate were applied in transient flow numerical simulations in a practical pumpedstorage power station based on transient flow theory and method of characteristics. The mechanism of closure law influencing the minimum pressure at the draft tube inlet was analyzed when a successive load rejection happened to find out the best closure law for the minimum pressure. The results show that a given closure law can decide the minimum pressure at the draft tube inlet to happen in the unit with first load rejection or the unit with late load rejection. Adopting a firstly slow then fast closing closure law can allow two units to have a nearly equal minimum pressure at the draft tube inlet at most unfavorable moments, respectively, showing a better law than the others. The procedure for obtaining such a closure law is as follows. Firstly, a closure law with twopiece line is selected. If the minimum pressure at the draft tube inlet in the unit with late load rejection is lower than in the unit with first load rejection, the law should be adjusted in such a way that the first piece line slope is increased and the second one is reduced. If not, the closure law should be adjusted vice versa until two units sharing approximately the same minimum pressure at the draft tube inlet.