A system designed to protect against generator under-voltage or overvoltage, through the use of an automatic hydraulic floodgate in a micro-hydro power plant, using induction generator in a stand-alone operation, was implemented in a micro-station hydroelectric power 30[kW]. The proposed system uses 24[V] batteries in a circuit and these are always kept ready using a battery charger, designed especially for the microstation operation. The time of descent and the gate rise time, are approximately one minute and a half. Tests were performed for the operation of the gate. The proposed protection system was robust, efficient, simple and reliable.