For the investor Hiden d.o.o., we replaced one of the two old Francis turbines with a new, more powerful Francis turbine with double runner on the river Kamniška Bistrica. On the existing penstock, where the old turbine was formerly located, we installed a turbine inlet valve (TIV), a pressure relief valve (PRV), a new Francis turbine, and a new generator. As already mentioned, the aggregate contains a PRV, which redirects the water flow through the by-pass pipe upon the rapid closure of the turbine. The distributor is quickly closed and the PRV is simultaneously opened and the water pressure in the penstock increases only by a minimal margin. The PRV then slowly closes and thus maintains a minimal increase in pressure in the penstock (approximately to 30%). The Francis turbine with a double runner also brings several other advantages: higher speed, twice bigger flow through the turbine, and almost negligible axial forces on turbine bearings. We have supplied and installed complete electro-mechanical equipment in the power house, from the concept to the unit commissioning. The project was completed at the end of 2016.