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1. INTRODUCTION:
Hydro (water) power is a conversional renewable source of energy which is clean, free from pollution and generally has a good environmental effect. Next to thermal power, hydro power is important in regard to power generation. The hydro-electric power plants provide 30 percent of the total power of the world. The total hydro-potential of the world is about 5000GW.In some countries (like Norway) almost total power generation is hydro based.
In hydro-electric plants energy of water is utilized to move the turbine which is turn runs the electric generators. The energy of water utilized for power generation may be kinetic or potential. The kinetic energy of water is its energy in motion and is a function of mass and velocity, while the potential energy is a function of the difference in level/head of water between two points. In either case continuous availability of the water in a basin necessity, to ensure this water collected in natural lakes and reservoirs at high altitudes may be utilized or water may be artificially stored by constructing dams across flowing streams. The ideal sit is one in which a good system of natural lakes with substantial catchment area, exists at a high altitude. Rainfall is a primary source of water and depends upon such factors as temperature, humidity, cloudiness, winds etc
1.1 ORGANIZATION:
Srisailam dam was constructed on the river Krishna, one of the major river systems in peninsula India. Srisailam dam forms the upper reservoir with a gross storage of 308TMCft (8700 million cubic meters).
The Srisailam dam has been constructed as the part of the Srisailam Hydro Electric project comprising the dam and power station on the right bank with an installation of 7 turbines, Hydra units of each 110MW. This power station is presently in operation and contributes about 2900 millions units every year, based on the availability of water.
1.2 GENERAL ARRANGEMENT OF THE EQUIPMENT IN THE POWER HOUSE:
The general arrangement of the equipment is shown in the diagram, plan of power house and working of the set is in vertical position. The set consists of a suspension type generator and Francis turbine coupled with it. This arrangement of unit provides the transfer of all axial loads through the thrust bearing installed on the upper cross bar on the generator to the foundation.
The water is delivered through a penstock diameter 6.096m. Disc valve is provided on the valve pit of the power house building .The valve is operated by two servomotors fed by valve at a pressure of 40 atmospheres. The oil pressure unit for disc valve has been located at EL.162.868 and the oil pipe lines from it are connected to the servomotors place at EL155.60 through control cabinet. The disc valve serves to stop the turbine for normal repairs of the turbine equipment and in emergency to prevent the indefinite turbine rotation at run way speed when the guide apparatus fails to operate for emergency closing, a device in turbine regulation system has been provided to protect the turbine against runway speed. When the governor of the turbine fails to operate, this emergency slide valve connects the ports of the servomotor of guide apparatus for its closing, directly with the pressure vessel of oil pressure unit.
The oil pipe from servomotor of guide apparatus passes through special block outs provided nearer the turbine pit entrance and rise up the emergency slide valve placed at EL 162.868 and then through main slide valve to the mechanical cabinet at EL 162.868 and then through main slide valve to the mechanical cabinet at EL 166.718 the oil pressure unit for the turbine has also been placed on this floor.
The turbine has a metallic spiral casing and a bent draft tube. A major portion of the draft tube knee has also been provided with metallic lining. The drainage of penstock, spiral casing and disc valve is carried through a common pipe to the draft tube. For de-watering of draft tube, a drainage valve 250 has been provided in an enclosure whose floor level is lower than that of the bottom of the draft tube, In its open position, the valve allows water in the draft tube to flow thought a 273 mm diameter pipe to the wet gallery located at AL 149.02 which is further connected to the draft tube de-watering sump. From this sump is pumped out to the tailrace. Other drainages and leakage of the station via from top cover, ejector, disc valve guide bearing cooler and oil cooler unit etc are led to the drainage channel at EL 155.60 which is further connected to the station drainage sump. Water from this sump is also pumped out to the tail-race. The drainage channel at EL 155.60 is being covered by the patron.
The de-watering of the turbine cover is carried out under gravity by self drainage system. Water flows from turbine cover through tooth of spiral casing to drainage channel at EL 155.60 as a standby an ejector has also been provided.
In the turbine pit, servomotors of guide apparatus and leakage unit have been placed. A passage of 1200 mm width from floor EL.162.868 to turbine pit has been provided. For easy movement in the turbine pit and inspection of the guide bearing cheque-red plates have been provided.
At EL. 155.60, where disc valve has been installed, an approach 1200mm, wide to draft tube manhole is provided. A similar approach has been provided diametrically opposite for access to the other manhole cover in the draft tube at EL. 154.18. The man-hole for the inspection inside the spiral casing has been provided in the outlet pipe of disc valve and is approachable from the floor at EL.155.60.
On the machine hall floor EL. 170.816 the electrical cabinet of governor and central cubicle are located. A hatch for erection and dismantling of disc valve has been provided in this floor which serves for the OPU also.
The gates operated by crane at downstream to close the draft tube are to be provided by the customer for repairs in the turbine. The hydro set components are serviced with two powerhouse cranes of 225/350 capacity each.
1.3 SPECIFICATIONS OF EQUIPMENTS IN SRBPH:
The main specifications of the turbine include the parameters like the type of turbine, diameter of runner, speed of rotation and runaway speed. All the parameters are list out in the table. This table also includes the availability of net heads in the power plant.