Solutions for the technical water supply system

The technical water supply system of a hydropower station is composed of the bearing of the hydroelectric generating set and the cooling water system of the generator. It has a direct impact on the safe operation of the unit as well as the economical operation of the power station. A technical water supply system should be designed according to the basic technical parameters of the hydropower station and the technical water supply parameters required by the devices, so that the design plan conforms to the specifications and requirements, and the units can work safely and properly in various conditions.

A technical water supply system supplies water for such devices as the guide bearing oil cooler on the generator, air cooler of the generator, thrust bearing oil cooler, and the guide bearing oil cooler of the water turbine. The cooling water in the technical water supply system of a hydropower station is very important for the safe operation of the units of the power station. Improper running of the cooling water may cause a higher temperature, alarm, or even shutdown to the units.

When the number of water heads in the hydropower station exceeds the specified water pressure, it is required to install a pressure relief device in the technical water supply system to reduce the automatic-flow water supply of the excessive water heads.

Automatic-flow decompression is the most economical technical water supply method for a hydropower station which has a high or middle water head. An automatic-flow decompression water supply system is composed of a water filter, reducing valve, and safety relief valve. It works like this: It directly intakes water from a penstock or volute. The water is then filtered in the water filter and sent to the reducing valve, or is decompressed and then filtered in the water filter. Finally, the filtered cooling water enters the units at the specified pressure and flow to cool the units.

To use this water supply method, selecting a proper reducing valve is very important. A stable and reliable piston reducing valve can provide stable and reliable cooling water for the units in a long period at a low maintenance cost and with a small workload. For example, a ZJY46H piston reducing valve can work stably for 6-15 years. It is pointed out by experts that using the water in an upstream reservoir for cooling instead of power generation does not conform to the standard of economic operation. However, considering that even a unit with an installed capacity of 16MW needs only a water consumption of 300m³/h to 400m³/h. Compared to the auxiliary power consumed by the water pump, such a water consumption is not high. On the other hand, the daily evaporation of the reservoir is unavoidable even no automatic-flow decompression water is used. In addition, an excellent reducing valve has great advantages over a water pump in terms of maintenance quantity, failure rate, and replacement period.

Many large hydropower stations, such as Xiangjiaba Hydropower Station and Goupitan Hydropower Station, adopt the water supply method of automatic -flow decompression.