Strategies to prevent entire voltage loss for chain-structured afflux station of small hydros

The entire voltage loss caused by the outlet line failure is studied for the chain-structured afflux station of small hydros. To prevent it, the impact of the asynchronous paralleling on grid and devices should be avoided, as well as the reclosing with lines, transformers, and even shutdown generator, which is off-loaded but still connected with grid. The concept of reclosing after separation is put forward, which separates the hydros first and re-closes then the lines. The solutions are given, such as the reclosing separation, the high-frequency separation, etc. and their adaptability to different operating modes, fault points, fault lines, fault types is analyzed. The possibility of maintaining the voltage of afflux station during its outlet line failure is discussed and the optimal solution is given: separate all stations except one with the best speed governor to maintain the station voltage and realize the fast automatic grid recovery.