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Case for the Equipment Selection of Pelton Hydropower Plant

 

ⅠSummary
Power station is diversion power station. Maximal head is 450.5m. Minimal head is 432.4m. Turbine rated head is 435.0m. Installed capacity is 2×13MW.
As per head variation range and total installed capacity, 2 units of 13MW vertical shaft impulse water turbine generators are determined to be installed at the power station after selection comparison. Turbine type is CJA237-L-140/4×11.5. Generator type is SF13-10/265. Rated running speed of unit is 600r/min. Governor is YDT-3000 type.
Rotor is the heaviest component in installation and maintenance of unit. As per its lifting weight, crane of major powerhouse shall be one 50t/10t, single trolley, overhead travelling crane, whose span L=13.5m.
 
ⅡPowerhouse Layout
Power station is diversion above ground powerhouse. Unit’s layout is in a column. From right to left is erection bay section and unit section. Major powerhouse of power station has a two-layer structure: from lower to upper is turbine layer and generator layer. Main run channel is on the upstream side of major powerhouse. Equipment lifting main channel and auxiliary run channel is on the downstream side. Stair leading to the turbine layer is separately set at powerhouse erection bay and unit section.
Water inlet ball valve and operation cabinet of turbine, governor oil pressure unit and water filter shall all be set at the upstream side of major powerhouse turbine layer. Exciter panel, machine side panel and dynamic panel shall be set at the downstream side of major powerhouse motor layer.
Excitation transformer, PT, generator switch, house service transformer switch and house service transformer shall all be set at the auxiliary powerhouse at downstream side of turbine layer major powerhouse. 2 low pressure air compressors, 2 medium pressure air compressors, medium air container, low pressure braking air container and low pressure repair air tank, oil purifier etc. shall be set at the turbine layer erection bay.
 
Determination of Major Dimensions of Major Powerhouse:
1. Length of the Powerhouse
Erection bay and generator layer are at the same elevation. Erection bay dimensions shall be determined as per the required dimensions of setting 4 major components as turbine head cover, runner, generator rotor and upper frame etc. in installation and maintenance, as well as the required dimensions for working space. Length shall be 12.25m. Unit spacing shall be controlled as per layout dimensions of jet water pipe and turbine spiral case, which is determined as 12m. Total building length of major powerhouse is 40m.
2. Width of the Powerhouse
Major powerhouse width is determined by composite factors like layout dimensions of turbine water inlet ball valve, turbine jet water pipe, turbine generator unit, as well as electromechanical equipment layout etc. For powerhouse upstream side width, layout of turbine water inlet ball valve, turbine inspection and maintenance channel request, and layout of debugging equipment shall be considered. Distance from unit centerline to upstream sidewall shall be determined as 6.75m. Powerhouse downstream side width shall be determined as per spiral case dimensions in –y direction, which shall meet large component lifting and channel requests in the meantime. Distance from unit centerline to downstream sidewall is 7.25m. Net width of major powerhouse is 14.0m. Span of overhead travelling crane is 13.50m.
3. Elevation of Each layer of Powerhouse
Calculating based on 0.0m installation elevation of turbine, elevation of draft tube baseplate is -4.40m. Turbine layer elevation is 1.10m. Generator layer elevation is 7.21m. Top track elevation of overhead travelling crane determined by the request of lifting turbine generator rotor is 15.15m.
 
Ⅲ Technical Water Supply System
Because that cooling mode of power station main transformer and air compressor in the major powerhouse is air cooling, technical water supply of this power station is applied mainly for the cooling and lubrication of 2 turbine generator units. Water consuming equipment of each unit includes: cooler of generator upper guide thrust bearing, air cooler, lower guide bearing and turbine guide bearing cooler etc.
 
1.       Water Source and Water Intake Way
Downstream tail water intake way is applied for the power station. 3 water intakes are set. Trash rack is set on each water intake to prevent ordure blocking.
2.       Technical Water Supply Mode
Head range of power station is 432.4-450.5m. Central water supply by water pump pressure is applied after analysis and comparison. 3 200S42A type (Q=198.0-311.0m³/h,H=31.0-43.0m ) centrifugal pumps are set in the system, among which 2 units work and another standby. 1 rotary water filter is set separately at outlet of each water pump to filter the water.
Diameter of general pipe of technical water supply is Φ219x6. The pipe goes through the powerhouse and leads to each unit. Electromagnetic valve is set on the water supply general pipe of each unit. And then the water is led to the upper and lower guide bearing coolers on generator, and turbine bearing cooler etc. Flow indicator is set on each branch drain to monitor unit water supply. Once cooling water is suspended, alarm signal shall be sent out instantaneously.
3.       Water Consumption of Equipment
Water consumption of equipment is estimated as per empirical formula. Total water consumption of 1 unit is 250m³/h.
4.       Living Water and Fire Water Supply System
Fire hydrant is set at the major powerhouse. Spray fire extinction mode is applied for two generators. In addition, concerning living and fire extinction request of the power station, 1 100m3fire pool is set at 55.95m elevation outside major powerhouse to meet the request of maximal fire extinction water consumption of equipment.
Supplement water source of fire pool is extracted from downstream tail water by fire extinction water pump. Two IS100—65—250A type (Q=56.0-112.0m³/h, H=65.0-76.0m) fire extinction water supply pumps in total are set in the powerhouse, among which 1 unit works and the other standby. One rotary water filter is set separately at the outlet of each water pump to filter fire extinction water.
One Ø159X4.5 living water supply pipe is set at the major powerhouse which goes through the whole powerhouse. Water is led to water spray fire extinction ring canal of each generator, transformer fire extinction water pipe and major pipe fire hydrant. Manual operation fire extinction mode is applied for generator water spray.
 
Ⅳ Turbine Oil System
Turbine oil system of power station mainly supplies turbine oil to ball valve pressure relieving device and governor oil pressure unit of 2 turbine units. No special turbine oil depot or special oil treatment equipment or special oil test equipment is set in this power station.
 
1.       Components of Turbine Oil System
Turbine oil system consists of 1 2m³ net oil tank, one 2CV—3,3/3.3—1 type gear oil pump, one 0.3 m³ gravity fuel tank, 1 1.0m³ middle oil tank and one leak oil tank per unit etc.
2. Oil Consumption of Unit and Oil Pressure Unit
Oil consumption of unit is provided by manufacturer. Before manufacturer data is acquired, the value shall be estimated as per the oil consumption of the same type unit with similar model and similar size. Oil consumption of each unit of this power station is about 8.0m³.
1.       Oil Consumption Equipment
Net Oil Tank
One net oil tank is set in the major powerhouse. Volume of the net oil tank is considered as per 25% of oil consumption of 1 unit, which is determined as 2m³.
2.       Middle Oil Tank
No special oil depot or oil treatment room is set in this power station. Concerning repairing convenience of the unit, 1 1.0 m³ oil tank is set, whose volume shall be determined as per the oil consumption of the upper guide bearing, which is the largest oil consumption component.
Gravity Fuel Tank
For fueling convenience in running, one 0.3 m³ gravity fuel tank is set.
3. Oil Pump
Concerning filling 1 unit with oil within 4h, and draining out the oil within allowable shutdown period of oil tanker, one 2CY—3.3/3.3—1 type gear oil pump shall be selected to be used in receiving new oil, equipment oil filling and oil draining. Its parameters shall be: flow Q=3.3m³/h; head H=0.33MPa.
 
Ⅴ Compressed Air System
Compressed air system of this power station is divided into two parts of low pressure compressed air system and medium pressure compressed air system.
1.       Low Pressure Compressed Air System
Low pressure compressed air system of this power station is divided into two parts of compressed air system and medium pressure compressed air system.
(1)    Air Consumption
For braking air consumption, the value of 1 unit is 0.8m³ as per formula.
Air consumption of maintenance and repair: 1 unit of S—100 pneumatic grinder is set at this power station, whose air consumption is 0.7m³/min. 1 unit of ZL—8 type pneumatic drill is set, whose air consumption is 0.65m³/min. Total air consumption of air toll is ∑Q=1.35m³/min.
(2) Air Container
To ensure reliability of unit braking air, special air container shall be set. Air container volume shall be guaranteed that when 2 units consume braking air synchronously, air pressure in the container shall be remained above the lowest braking air pressure. Acquired volume of air container shall be 2.0m³ by calculation as per formula. Working pressure shall be 0.8Mpa.
(3)    Selection of Air Compressor
Productivity of air compressor shall be 1.36m³/min by calculation as per formula. Rated discharge pressure of air compressor shall be 0.86 MPA. 2 SLG15 type air compressors shall be selected, among which one is major and the other standby. The discharge rate: Q=1.5m³/min. Discharge pressure shall be P=0.86MPA.
(4)    Running Mode of Equipment
Two air compressors are set in this system, among which 1 unit works and the other standby. To ensure reliable air source in unit braking, two air containers are set corresponding to two air compressors, among which one air container is specially used to supply air for unit braking, and the other is used to supply air for unit repair. Startup and shutdown of two air compressors are controlled by pressure annunciator on air container.
 
2.       Medium Pressure Compressed Air System
Medium pressure compressed air system supplies air to the governor oil pressure unit and oil pressure unit of water inlet ball valve of 2 units. Actuating pressure is 2.5MPA. Primary pressure air supply mode is applied
(1)    Selection of Air Compressor
Rated discharge pressure of air compressor is determined as 3.0MPA. Productivity of air compressor is 0.3m³/min by calculation as per formula . two WF-0.3/30 type air compressors shall be selected.
Air Container
(2)    One medium pressure air container is set, whose volume is 1.5m³. Working pressure is 2.5MPA.
Running Mode of Equipment
Two air compressors are selected, among which 1 unit works and the other standby. At the first time of gas charging after oil pressure unit is installed or repaired, two air compressors shall work synchronously. Manual air admission mode is applied for oil pressure unit in running.

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