Kallada Hydro Electric Power Project, Thenmala

   I was so fortunate to be able to visit the hydroelectric power project Thenmala. The following details will give you an update and details about the Kallada Hydro Electric Power Project. It was a herculean task for us to get a permission to visit the project because due to some strikes going on at that place. Anyway the visit totally worth as we spend a whole day on the project site. Here you can find he details of the project.

The Thenmala generating station is located in the Kollam district near Kallada River. The rated capacity of the plant is 15MW.It has an annual generation of 65MU (Million Unit).This generating station consists of two very powerful generators of 7.5MW each. The name of the project at Thenmala generating station is called Kallada Hydro Electric Project. The dam has a cross sectional area of 24 square km with a height of 118m.The power house also occupies 11/220kv transformer substation for transmission of power.

IMPORTANT COMPONENTS OF GENERATION

·         Kaplan tube

·         Alternator

·         Gear arrangement

·         Penstock

·         Draft tube

·         AGC

                                                                                                                                                         

	Technical Details
Year of commissioning : 1993
No. of Unit x Capacity	: 2x 7500KW
Gross Head	: 43m
Net Head	: 40m
Type Of Project	: Dam Toe Based
Type of Diversion	: Penstock Inlet
Catchment area	: 225 Sq km
Turbine Type	: Kaplan
Turbine Manufacturer	: BHEL
Coupling	: Direct
Generator manufacturer  : BHEL
Generator voltage	: 11KV
Type of governor	: Electromechanical
Governor Manufacturer : BHEL
Power Evacuation Level  : 33KV
Unit Operating	: At design capacity

 KAPLAN TURBINE

If the water flows parallel to the axis of the rotation of the shaft, turbine is known as axial flow turbine. And if the head at inlet of turbine is the sum of pressure energy and kinetic energy and during the flow of water through runner of pressure energy is converted into kinetic energy. The turbine is known as reaction turbine. For axial flow reaction turbine, the shaft of turbine is vertical. The lower end of the shaft is made larger which is known as hub or boss. The vanes are fixed to the hub and hence act as runner for axial flow reaction turbine.

If the vanes on the hub are adjustable the turbine is known as Kaplan turbine. This turbine is suitable where a large quantity of water at low heads is available.

The main parts of Kaplan Turbine are:

1. Scroll casing

2. Guide vanes mechanism

3. Hub with vanes or runner of turbine 

4. Draft Tube.

The water from penstock enters the scroll casing and then moves to the guide vanes .From the guide vanes water turns through 35 degree and flows axially through the runner. Kaplan blades used here can be movable type .Here 20 guide vanes and 6 blades are used. Cooling system used for the Kaplan turbine contains water cooling tubes. Kaplan turbine used here is hydro turbine type.

DETAILS OF KAPLAN TURBINE:

Type                       : Horizontal

Rated Head           : 43m

Discharge Speed    : 18m/s

Run Away Speed   : 1100 rpm

Output                    : 7.8 MW

ALTERNATOR

An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current. Alternator generates electricity by the same principles as DC generators, namely, when the magnetic field around a conductor changes a current is induced in the conductor. Typically a rotating magnet called the rotor turns within a stationary set of conductors wound in coils on an iron core, called the stator. The field cuts across the conductors, generating an electrical current, as the mechanical input causes the rotor to turn. Alternator used in central power stations may also control the field current to regulate reactive power and to help stabilize the power system against the effects of momentary faults.

               

PENSTOCK

Penstocks are pipes of large diameter which carry under pressure from the storage reservoir to turbines .These pipes are made of reinforced concrete.

When water is flowing from head to the turbine, a loss of head due to friction between the water and the penstock occurs. There are other losses also such as loss due to bend, Pipe fittings, loss at entrance of penstock etc.

DRAFT TUBE

The pressure at the exit of the runner of the reaction turbine is generally less than atmospheric pressure. Thus the water at exit of the runner cannot be directly discharged to the trail race. A pipe of gradually increasing area is used for discharging water from exit of the turbine to the tail race. The pipe gradually increasing area is called Draft Tube. One end of the draft tube is connected to the outlet of the runner while the other end is submerged below the level of water in the tail race.

AUTOMATIC GAIN CONTROL

Automatic gain control (AGC) is an adaptive system found in many electronic devices .The averages output signal level is fed back to adjust the gain to an appropriate level for a range of input signal levels.

STARTING AND STOPPING OF GENERATORS

Starting:

1.  Ensure that:

1.    Draft tube is open

2.    Bypass valve of butterfly valve is open

3.    Air is blown from intermediate tube

4.  3 phase 11KV Supply and 110V dc

5.  Valves in the generator bearing cooling waterline, GB cooling line, Thrust bearing and guide lubrication line, water lines, to seal are open

1.      Switch on AC&DC supply to TGCP,R&A panel DC supply to AVR · Lubrication pump starts working-induction flashes.

· Hydraulic pressure pump starts

·         When the lubrication oil level reaches the minimum level in the overhead tank the indication stops flashing and glows permanently

2. Switch on GB oil pump and ensure the oil flow from the pressure gauge reading.

3. Press start push button

·         Start push button flashes fast

·         BFV starts opening

4. Press ‘Load Regulation ‘push button’ & ‘Runner Optimizing’ push button.

·         When the BFV opens fully, the runner & guide vanes open automatically, the machine stars rotating and reaches the steady speed of 428rpm.During opening process of BFV, if we want to run the machine, press ‘stop’ button. BFV keeps on opening and machine does not start till we give another press on ‘start’ button.

5. Keep the guide wheel opening limiter on TGCP at about 50%

6. Switch on auxiliary supply of AVR, select AVR-1 or AVR -2 or manual mode. Switch on

‘main switch” on AVR panel.

7. Keep incomer Breaker spring charged

8. Switch on synchronizing panel, Machine voltage, bus voltage, machine frequency and bus frequencies are shown in panel, synchronoscope needle starts rotating. Sychroscope needle starts rotating.

9. Press the guide wheel HAND OPERATION button

10. Equalize the machine frequency and bus frequency by opening/closing

11. Equalize the machine voltage and bus voltage by potentiometer/variac on AVR panel.

12. Switch on the incomer VCB.

13. Switch off synchronizing panel

14. Press ‘ Load Regulation’ button

15. Set the voltage to the rated level.

16. Set the opening limiter to the required level viewing the load current.

17. Observe and monitor all meters, gauges and scanners regularly.

Stopping:

1. Bring down the load current using the opening limiter.

2. When the current reaches almost zero, switch off the VCB

3. Switch off AVR main switch, auxiliary supply put back the pot/variac to zero.

4. Put the BFC Selector switch in HAND press ‘close’ button

5. Close bypass value of BFC

6. Close cooling water line , stop GB oil pump

7. Switch off AC,DC supply , TGCP, AVR panel , R&A panel

8. Release the hydraulic pressure using either of the 2 knobs provided at the hydraulic governor

9. Tighten the knob when pressure comes to zero.

Thus being an engineering student, it was necessary to understand how power was generated in a typical hydel power plant. From this visit I understood the power generation in the hydel power plant in much more critical way.