Expulsion of water from the turbine runner on switching a turbo-generator to a synchronous condenser regime

Conclusions

• 1. The fastest and most complete possible expulsion of water from the turbine runner is a necessary condition for switching a unit to the SC regime.

• 2. The water should be expelled by compressed air. The pneumatic systems of hydroelectric stations intended for this purpose are designed for an initial pressure of 8 and 40 atm.

• 3. The air collectors should consist of large-diameter pipes placed inside the powerhouse along one of the galleries of generator room.

• 4. For delivery of compressed air to the runner pit it is recommended to use a slide valve with a hydraulic drive at a pressure of 8 atm and plug cock with a servomotor at a pressure of 40 atm.

• 5. For automatic monitoring and maintenance of the level of expelled water in the draft tube it is recommended to use a DRP level regulator, produced by “Soyuzénergoavtomatika,” or the ORGRÉS level-regulating float relay.

• 6. The existing design of valves admitting atmospheric air under the runner which are installed on the hollow shaft of mixed-flow turbines do not meet the operating requirements of the unit in the active and SC regimes.

• 7. In the case of switching high-head units with low-speed turbines to the SC regime it is necessary to expel the water from the spiral casing as well was from the runner pit, since only in this case is complete expulsion achieved.