2.8 Technical Water Supply and Drainage System and Fire-fighting Water Supply System

2.8.1

The technical water supply system consists of the water supply for the cooling and lubricating of the main and auxiliary equipment such as hydraulic turbine generator units/motor-pump units,water-cooled transformer,oil sump tank of the oil pressure unit and water-cooled air compressor and the water supply for the secondary cooling water of the internal cooling generator.Technical water supply system shall be arranged reasonably,and its operation shall be safe,reliable,and automatic.

2.8.2

The technical water supply system shall be provided with a reliable main water source and a standby one.The water source shall be selected reasonably according to the equipment requirements for water consumption,pressure,quality and tempera ture,in combination with the actual conditions.The water shall be purified if its quality fails to meet the requirements.

2.8.3

The technical water supply mode of a hydropower plant or a pumping station shall be determined in accordance with the following provisions.

1 The technical water supply mode of a hydropower plant should be determined in accordance with the head:

1)Pumping supply mode should be applied if the minimum head is less than 15m.

2)Gravity water supply mode should be applied if the net head is 15 to 70m.

3)Gravity flow with pressure relief or other water supply mode should be applied if the net head is 70 to 120m.

4)If the net head is above 120m,the water supply mode shall be determined by technical and economic comparisons.Pumping supply or other supply mode should be applied.

5)In the case that a single supply mode is uneconomical or does not meet the need of equipment due to large variation of head,the combined water supply mode may be applied.

6)An in-between pond water supply mode may be applied in order to obtain more stable water supply pressure if the arrangement of the hydropower plant is practical and economical.

2 Water tower or pond supply mode may be applied if the arrangement of the pumping station is practical and economical,and the effective volume shall meet the following requirements:

1)For axial flow and mixed flow pumping stations,15min water consumption of the entire station shall be taken.

2)For centrifugal pumping station,2-4h water consumption of the entire station shall be taken.

2.8.4

For the gravity flow with pressure relief water supply system and the head cover water supply system in the hydropower plant,pressure relief device shall be provided.

2.8.5

For a hydropower plant with large reservoir drawdown,the water shall be taken from different elevations on the basis of the sediment concentration and water temperature of the reservoir,and shall meet the water supply requirement for the power generation at early stage.For an underground hydropower plant with a long tailrace tunnel,the intake locations shall be in stable water pressure region,and not affected by the pressure pulsation of the draft tube when taking water from the draft tube.

2.8.6

Trash racks shall be provided at the water intakes of the technical water supply system,the cleaning measures should be provided.The measures for maintenance and replacement of the first service valve on the inlet pipe of the intakes shall be taken.

2.8.7

Drainage system consists of unit dewatering system and powerhouse drainage system.For large and medium-scaled hydropower plants,unit dewatering system and powerhouse drainage system should be arranged separately.For the pumping station,unit dewatering system and powerhouse drainage system may be set separately.The drainage and dewatering systems may share one set of facilities through technical and economic verification.Once a set of facilities is shared by the two systems for a hydropower plant or a pumping station,the safety measures shall be taken to prevent tailwater from flooding the powerhouse.If possible,the gravity drainage mode shall be preferred.

For a hydropower plant or a pumping station with an underground powerhouse,unit dewatering system and powerhouse drainage system shall be arranged separately.

2.8.8

The unit dewatering system of a hydropower plant or a pumping station may be of the direct or indirect drainage mode.For direct drainage mode,the diameter of the drain pipe connected to each draft tube or to pump unit inlet passage shall meet the requirement of pump discharge,and desilting measures shall be taken as well.

For indirect drainage mode,the effective volume of a sump shall be sufficient for one pump's 10-15min discharge.

For an underground powerhouse or a hydropower plant with higher tailwater level,direct model should be applied.

2.8.9

The rated discharge of a dewatering pump shall be deter mined according to the discharge and the time required for one unit maintenance.The dewatering duration should be 4-6h in general,and may be prolonged appropriately if it is required to dewater the accumulated water in a long tailrace tunnel.At least two dewatering pumps shall be set and they shall be service pumps.In the case that two pumps are applied,each pump capacity shall exceed the total leakage of the upstream and downstream gates.

2.8.10

The drainage system in the powerhouse shall be safe and reliable and shall be operated automatically,and water level alarm device shall be set in the drainage sump.And the powerhouse drainage system shall be separated from the plant drainage system.The plant drainage system should be arranged outside the powerhouse.

2.8.11

The effective volume of drainage sump may be deter mined by the total leakage of the powerhouse in 30-60min,and the effective volume should be appropriately increased if possible.

2.8.12

The discharge of drainage service pump shall be deter mined according to the effective volume of the sump,the leakage volume and water discharge time.The water discharge time should be 20-30min.The standby pump shall be provided for the drainage system and its discharge should be the same as the service pump.

Deep well pump or submerged pump should be selected for drainage pump.

2.8.13

The drainage sump shall be able to collect the leakage water at the lowest floor of the powerhouse and the alarming water level of the sump shall be lower than the ground elevations of the access gallery at the lowest floor,the operating gallery and the places installed with permanent equipment.

2.8.14

Drainage pipe outlet should be 2m lower than the low est tailwater level in cold area,and the valve at the drainage pipe outlet submerged under the water shall be provided with maintenance and replacement measures.

2.8.15

The drainage gallery and sump of hydropower plants or pumping stations located on sediment-laden rivers shall be provided with desilting devices.

2.8.16

Hydropower plant and pumping station should be pro vided with independent fire-fighting water supply system which may be supplied by gravity flow,pump or fire pool,etc.For gravity water supply,the number of intakes shall not be less than two.For pumping supply,standby pump shall be provided and the capacity shall not be less than that of the service pump.For fire pool,its volume shall meet the requirement for fire-fighting water consumption during the fire.

Fire duration for a powerhouse shall be 2h.Fire duration for an outdoor switchyard shall be 1h.Fire duration for a hydraulic turbine generator unit shall be 10min.Fire duration for an oil-immersed transformer,large cable chamber or an oil tank shall be 24min.

2.8.17

The rated discharge and pressure of a fire-fighting wa ter supply system should be determined as per the larger one between the maximum one-time fire-fighting water consumption and the maximum pressure to extinguish one set of E&M equipment or one building,and appropriate margin should be provided.

2.8.18

The design of fire-fighting water supply for a hydro power plant or a pumping station shall conform to the stipulations in SDJ 278.