Selection of Turbines and Power House Dimesioning

SELECTION OF SELECTION OF HYDRO-TURBINESHYDRO-TURBINESand Power House and Power House

dimensioningdimensioningby by

S.KrishnamurtyS.Krishnamurty

ENERGY INFRATECH PVT. LTD.ENERGY INFRATECH PVT. LTD.

Reaction Turbine

• Francis Turbine • Kaplan Turbine • Bulb Turbine

Hydraulic Turbine

Classification of Hydraulic Classification of Hydraulic TurbineTurbine

Impulse Turbine

Pelton TurbineTurgo Turbine

Cross flow Turbine

BASIC INPUTS FOR TURBINE BASIC INPUTS FOR TURBINE SELECTION AND RATINGSELECTION AND RATING

1.HEAD (H)

2.DISCHARGE(Q)

Gross HeadGross Head (Hg) (Hg) – It is the difference in – It is the difference in elevation between the water levels of the forebay elevation between the water levels of the forebay and tail race (for Reaction Turbine) or Centre Line and tail race (for Reaction Turbine) or Centre Line of Runner( For Impulse Turbine).of Runner( For Impulse Turbine).

Net HeadNet Head(Hn)(Hn) – It is the gross head less all – It is the gross head less all hydraulic losses except those chargeable to the hydraulic losses except those chargeable to the turbine. Net head is the head available for doing turbine. Net head is the head available for doing work on the turbine. work on the turbine.

HEAD HEAD as per IS 12800(Part 1):1993as per IS 12800(Part 1):1993


Maximum Net HeadMaximum Net Head (Hmax) (Hmax) - It is the gross head - It is the gross head resulting from the difference in elevation between the resulting from the difference in elevation between the maximum forebay level and the tail race level (Reaction maximum forebay level and the tail race level (Reaction Turbine) or Centre Line of Runner for Impulse Turbine Turbine) or Centre Line of Runner for Impulse Turbine without spillway discharge and with one unit operating at without spillway discharge and with one unit operating at no load speed. Under this condition , Hydraulic losses are no load speed. Under this condition , Hydraulic losses are negligible and may be neglected.negligible and may be neglected.

Minimum Net HeadMinimum Net Head (Hmin) (Hmin) – It is the net head resulting – It is the net head resulting from the difference in elevation between the minimum from the difference in elevation between the minimum forbay level and the tail race level with all turbine operating forbay level and the tail race level with all turbine operating at full gateat full gate


Rated Head (Hr)Rated Head (Hr) - It is the head of which the specifications require - It is the head of which the specifications require that the turbine operating at full gate shall produce sufficient power that the turbine operating at full gate shall produce sufficient power to deliver the name plate power output. to deliver the name plate power output.

It is the 2/3It is the 2/3rdrd of the difference between FRL and MDDL above the of the difference between FRL and MDDL above the MDDL. Basically it is assumed that the volume of water above this MDDL. Basically it is assumed that the volume of water above this level is same as below this level as the shape of pondage goes on level is same as below this level as the shape of pondage goes on decreasing. So the probability of this head to available is more .decreasing. So the probability of this head to available is more .

Design Head (Hd)Design Head (Hd) – – It is the net head under which the turbine reaches its peak It is the net head under which the turbine reaches its peak

efficiency at synchronous speed; Usually it is specified as efficiency at synchronous speed; Usually it is specified as =Hd=Min. Net Head+(2/3)*(Max. Net Head-Min. Net Head).=Hd=Min. Net Head+(2/3)*(Max. Net Head-Min. Net Head).This is the head which determines the basic dimensions of the This is the head which determines the basic dimensions of the turbine and therefore of the power plant.turbine and therefore of the power plant.

For optimum operation benefits the Design Head &Rated Head For optimum operation benefits the Design Head &Rated Head are kept same.are kept same.

Discharge (Q)Discharge (Q)--It is the rate of volume of water coming to turbine. It is the rate of volume of water coming to turbine. It depends on catchmentsIt depends on catchments

As per USBR

Specific SpeedSpecific SpeedSpecific Speed: Specific Speed is a typical characteristic where all Specific Speed: Specific Speed is a typical characteristic where all

runners of a given specific speed are similar in form and vary only runners of a given specific speed are similar in form and vary only in size. This Speed form the basis of Classification of Turbines. It in size. This Speed form the basis of Classification of Turbines. It can be defined as the speed of a homologous turbine of such a can be defined as the speed of a homologous turbine of such a size that it would develop unit power at unit head.size that it would develop unit power at unit head.

Ns =(N x (P)^0.5) / Hd^(5/4)Ns =(N x (P)^0.5) / Hd^(5/4)WhereWhereNs= Specific Speed in rpmNs= Specific Speed in rpmN = Unit Speed in rpmN = Unit Speed in rpmHd= Design Head in MetersHd= Design Head in MetersP = Rated PowerP = Rated Power

..

Factors affecting selection of Factors affecting selection of hydraulic turbineshydraulic turbines

1.Head1.Head :- :- 250m and above-Pelton250m and above-Pelton 150-250m-Pelton /Francis150-250m-Pelton /Francis

60-150m-Francis 60-150m-Francis 30-60m -Francis/Kaplan30-60m -Francis/Kaplan15-30m -Kaplan15-30m -Kaplan2-15m -Bulb/Tubular2-15m -Bulb/Tubularup to 15m-Propellerup to 15m-Propeller

2.Discharge2.Discharge:-:- Low Discharge-PeltonLow Discharge-PeltonMedium Discharge-FrancisMedium Discharge-FrancisHigh Discharge-KaplanHigh Discharge-Kaplan

3.Specific speed3.Specific speed:-High specific speed is essential when head :-High specific speed is essential when head is low and output is large because otherwise rotational is low and output is large because otherwise rotational speed is low which means cost of generator and power speed is low which means cost of generator and power house more.house more.

It is classified asIt is classified as 30-150 rpm –Pelton30-150 rpm –Pelton80-300 Rpm-Francis80-300 Rpm-Francis30-1000Rpm-Kaplan30-1000Rpm-Kaplan

Figure depicting selection of turbine

on the basis of head

4.Site characteristics4.Site characteristics:-Type of rock available and :-Type of rock available and depth up to which the rock is available.depth up to which the rock is available.

5.Type of Plant5.Type of Plant:-Peak Load Plant or Base Load Plant:-Peak Load Plant or Base Load Plant6.Water Quality (silt6.Water Quality (silt):-If the turbine lies in the ):-If the turbine lies in the

overlapping zone of Francis and Pelton the silt criteria overlapping zone of Francis and Pelton the silt criteria needs to be seriously considered.needs to be seriously considered.

7.Cost:-7.Cost:-The minimum cost is preferred taking into view The minimum cost is preferred taking into view above factors also.above factors also.

8.Manufacturing Difficulty8.Manufacturing Difficulty:-That turbine cant be taken :-That turbine cant be taken which is very typical to make.which is very typical to make.

9. Cavitations9. Cavitations:-The installation of reaction turbine over :-The installation of reaction turbine over Impulse turbine is affected by the cavitation.Impulse turbine is affected by the cavitation.

10.Maintainence:-10.Maintainence:-The turbine selected should be also The turbine selected should be also easy to maintain. Pelton is easy in maintenance as easy to maintain. Pelton is easy in maintenance as compared to Francis Turbine.compared to Francis Turbine.

11.Time out of operation:- 11.Time out of operation:- The case of repair isThe case of repair is normally related to sand erosion.normally related to sand erosion.

Classification of Turbine on the Classification of Turbine on the basis of Discharge & Headbasis of Discharge & Head

Classification on the basis of Classification on the basis of Head & Specific speedHead & Specific speed

Pelton Turbine Kaplan TurbineFrancis Turbine

Turbine selection on the basis of discharge (by VA Tech Hydro)

Axial Turbine Bulb Turbine

Turbine selection on the basis of discharge & head(by VA Tech Hydro)

Efficiency Comparision-Different Efficiency Comparision-Different TurbinesTurbines …… ……(as per USBR)(as per USBR)

Efficiency of various turbine of our projects

Malana-II SainjPatikar

i Teesta-III

50X2 MW 2X2.5 MW 8X2 MW 200X6 MW

Type of turbine Pelton Francis Pelton Pelton

As per contract 91.4 91 93 92.2

As per actual Field test Not yet 92 89.04 Not yet

Conflicts between Pelton & Conflicts between Pelton & FrancisFrancis

When the head is between 150 & When the head is between 150 & 250m250m

1. 1. DischargeDischarge :-If this is high Francis is :-If this is high Francis is preferredpreferred

2. 2. EfficiencyEfficiency:-The efficiency of Francis :-The efficiency of Francis is more at full load around 96% is more at full load around 96% while Pelton around 90%.while Pelton around 90%.

3. 3. Time out of operationTime out of operation:-Dismantling :-Dismantling and assembly of the sand eroded and assembly of the sand eroded parts takes shorter time for Pelton parts takes shorter time for Pelton than for Francis turbines. Therefore than for Francis turbines. Therefore Pelton turbines will normally be Pelton turbines will normally be preferred where much sand erosion preferred where much sand erosion is expected. However, this again is expected. However, this again depends rather strongly on the depends rather strongly on the plant’s operation schedule.plant’s operation schedule.

As per USBR

If one or more turbines are stopped If one or more turbines are stopped for a long period of for example for a long period of for example two months a year, Francis two months a year, Francis turbines may be chosen even if turbines may be chosen even if the water has a high sand the water has a high sand content because there will be content because there will be enough time for an annual enough time for an annual repair.repair.

4.Site Characteristics4.Site Characteristics:-:-Installation cost in case of Installation cost in case of Francis Turbine also increased Francis Turbine also increased when the rock available is at when the rock available is at very high depth. So we have to very high depth. So we have to excavate up to that depth and excavate up to that depth and even concrete up to required even concrete up to required level. So additional excavation level. So additional excavation cost and concreting cost comes cost and concreting cost comes into pictureinto picture

As per USBR

Pelton vs. FrancisPelton vs. Francis

5.Operation under part load5.Operation under part load6.Cost comparison 6.Cost comparison

The cost of machine decreases as the speed increases.

As per USBR

Conflict between Francis & Conflict between Francis & KaplanKaplan

When the head is between 30 When the head is between 30 & 60m& 60m

1.In general the Kaplan 1.In general the Kaplan turbines are chosen for turbines are chosen for heads below 30 m. But heads below 30 m. But since its part load since its part load efficiency is more it is well efficiency is more it is well extended up to low head extended up to low head Francis turbineFrancis turbine

2. Kaplan turbine offers also 2. Kaplan turbine offers also an advantage with its an advantage with its smaller dimensions for a smaller dimensions for a certain capacity than the certain capacity than the corresponding Francis corresponding Francis turbine. Especially for large turbine. Especially for large machines where capacities machines where capacities of 200 – 500 m3/sec are of 200 – 500 m3/sec are wanted the Kaplan turbine wanted the Kaplan turbine is chosenis chosen

As per USBR

3. The upper 3. The upper economic and economic and practical limit for the practical limit for the Kaplan turbine head is Kaplan turbine head is in the range of 60m, in the range of 60m, though extreme cases though extreme cases of 70 - 75 m have of 70 - 75 m have been planned for this been planned for this turbine type as well. turbine type as well. The head limit is The head limit is caused by mechanical caused by mechanical strength problems in strength problems in hub and blades.hub and blades.

Conflict between Kaplan & BulbConflict between Kaplan & BulbFor low heads Bulb turbines will be For low heads Bulb turbines will be

an alternative to the Kaplan an alternative to the Kaplan turbines.turbines.

1.More favorable flow 1.More favorable flow conditions:-conditions:-. These favourable . These favourable flow conditions have the effect flow conditions have the effect that the runner diameter of a that the runner diameter of a Bulb turbine may be made 15 % Bulb turbine may be made 15 % smaller than for a Kaplan turbine smaller than for a Kaplan turbine under otherwise equal under otherwise equal conditions. conditions.

2.Less Cavitation2.Less Cavitation:-The flow :-The flow conditions will also reduce the conditions will also reduce the cavitation risk for the Bulb cavitation risk for the Bulb turbine, which means a less turbine, which means a less submergence is needed than for submergence is needed than for the Kaplan turbine.the Kaplan turbine.

3.Size of Power House3.Size of Power House:-:-The Bulb turbine is still The Bulb turbine is still more favourable if only more favourable if only one unit shall be built one unit shall be built because the scroll casing because the scroll casing of a Kaplan turbine makes of a Kaplan turbine makes the power station much the power station much wider. The Bulb turbine wider. The Bulb turbine will however, reach an will however, reach an upper limit design head upper limit design head because of the because of the concentrated hydraulic concentrated hydraulic load on the concrete load on the concrete foundation through the foundation through the ribs. Thus the pressure ribs. Thus the pressure will be limited to 15 - 20 will be limited to 15 - 20 m head for this turbine m head for this turbine type.type.

Classification of TurbinesClassification of Turbines

Type of Type of machinemachine

Head Head variation variation

Percent of Percent of rated rated headhead

Load Load variation variation percent of percent of

rated rated outputoutput

Specific Specific Speed m-Speed m-

mhpmhp

Peak Peak efficiencefficienc

yy

PeltonPelton 120 to 80120 to 80 50 to 10050 to 100 15 to 6515 to 65 9090

FrancisFrancis 125 to 65125 to 65 50 to 10050 to 100 60 to 40060 to 400 9393

DeriazDeriaz 125 to 65125 to 65 50 to 10050 to 100 200 to 400200 to 400 9292

KaplanKaplan 125 to 65125 to 65 40 to 10040 to 100 300 to 800300 to 800 9292

PropellerPropeller 110 to 90110 to 90 90 to 10090 to 100 300 to 800300 to 800 9292

BulbBulb 125 to 65125 to 65 40 to 10040 to 100 600 to 1200600 to 1200 9292

as per IS 12837:1989 Clause as per IS 12837:1989 Clause 5.15.1

Power House sizingPower House sizing

As pert IS 12800, The overall dimensions of As pert IS 12800, The overall dimensions of Power house mainly depend upon the following:Power house mainly depend upon the following:

1.1. Overall dimension of the turbine, draft tube and Overall dimension of the turbine, draft tube and scroll case;scroll case;

2.2. Overall dimensions of the generator;Overall dimensions of the generator;

3.3. Number of Units in the power house; andNumber of Units in the power house; and

4.4. Size of erection baySize of erection bayNote: Provision for inlet valve, erection of rotor and un-tanking of Note: Provision for inlet valve, erection of rotor and un-tanking of

transformers should be made in such a way that space required is transformers should be made in such a way that space required is minimum without impairing the operational and maintenance minimum without impairing the operational and maintenance requirementsrequirements..

A. Length of Power HouseA. Length of Power House

It depends upon the It depends upon the

1.1. Unit SpacingUnit Spacing

2.2. Length of erection bayLength of erection bay

3.3. Length required for the EOT Crane to Length required for the EOT Crane to handle the last unithandle the last unit

1.Unit Spacing(Us)1.Unit Spacing(Us)

Inner diameter of the generator Inner diameter of the generator barrel is determined as per the barrel is determined as per the norms and outer diameter of the norms and outer diameter of the barrel is taken as barrel is taken as 0.5 to 1.5m more 0.5 to 1.5m more depending upon the size of machine.depending upon the size of machine.

As per Std. Malana II As per Std. Teesta III

Outer diameter of barrel

7900-8900mm 8400mm =10500 – 11500mm

12000mm

A clearance of 1.5 to 2m shall be added on A clearance of 1.5 to 2m shall be added on either side of the extremities of the either side of the extremities of the generator barrel.generator barrel.

These clearance should be such that These clearance should be such that concrete thickness on either side of scroll concrete thickness on either side of scroll case should be 1 to 1.5m in case of fully case should be 1 to 1.5m in case of fully embedded steel scroll case.embedded steel scroll case.

Usually spacing with scroll/spiral case Usually spacing with scroll/spiral case clearance is more and will be basis.clearance is more and will be basis.As per

Std.Malana II As per Std. Teesta III

Spiral case overall diameter

- 12183mm - 16484mm

Us 14183-15183

20000mm(as CW sump is between units)

18484-19484 24000mm

Malana II HEP

Teesta III HEP

2.Length of Power House2.Length of Power House A)Length of service bay A)Length of service bay LsLs : : 1.5times Us1.5times Us B)Length required for EOT crane to handle the B)Length required for EOT crane to handle the

last unit last unit kk : 3 to 5 m: 3 to 5 m C)Length of Control Block C)Length of Control Block LcbLcb C)Length of Power House:C)Length of Power House: No. of units x Us +Ls +k + LcbNo. of units x Us +Ls +k + Lcb


Unit Spacing

15183 20000mm 19484 24000mm

Length of service bay

=1.5x15183=22774mm

18700mm =1.5x19484=29226

48000mm

Length of control block

12000mm 18950mm

Length of Power House

=2x20000+18700+5000+12000=75700

67500mm =6x24000+48000+5000+18950=198890mm

214300mm

Malana II HEP

Teesta III HEP

3.Width of Power House3.Width of Power House On the upstream side provision should be made for the following:On the upstream side provision should be made for the following: a)A clearance of about a)A clearance of about 1.5 to 2 m 1.5 to 2 m for concrete the upstream of for concrete the upstream of

scroll casescroll case b)In case the main inlet valve is also accommodated in the b)In case the main inlet valve is also accommodated in the

power house, a valve pit of approachable size should have to be power house, a valve pit of approachable size should have to be provided as per IS 7326(Part 1) and IS 7332(part 1)provided as per IS 7326(Part 1) and IS 7332(part 1)

As per Std Malana II As per Std. Teesta III

Distance of spiral case from centerline D,E

4534,5183

4376,6373

5828,6477

8330,8375

MIV Dia/width W 1200 1300 1900 1900

Width of spherical valve :Max=2.6(MIV)

=2.6x1200=3120

5126 =2.6x1900=4940

5890

Width on U/s side=D+W+2000

=9654 =9400 =12768 11500

Width on D/s side=E+2000

=7183 =8100 =9977 =10000

Total Width =16837 =17500 =22745 =21500

c)The spaces as indicated against item(a) are supposed to be sufficient for accommodating the auxiliary equipment also but may have to be reviewed considering the layout of essential equipment and operational requirements.

Malana II HEP

Teesta III HEP

3.Height of Power house3.Height of Power house Height coefficient Height coefficient

K3 = 0.65 or 0.75 or 0.85 K3 = 0.65 or 0.75 or 0.85 Height of the Load Bearing Bracket Height of the Load Bearing Bracket

Hj =K3 x sqrt of Df (for Suspension) and K3 X sqrt Hj =K3 x sqrt of Df (for Suspension) and K3 X sqrt of (Di for umbrella) of (Di for umbrella)

Distance between centre line of turbine and Distance between centre line of turbine and machine hall floormachine hall floor H2 =Hj+Lf+6.75H2 =Hj+Lf+6.75

Total Height from datum line to top of Total Height from datum line to top of generator generator H =H1 + H2 H =H1 + H2

Height of largest package to be liftedHeight of largest package to be lifted around 7 to 8.5 around 7 to 8.5

Height of slipring housing above machine Height of slipring housing above machine hall floor hall floor around 1 to 1.5m around 1 to 1.5m

Hook allowance Hook allowance around 2.5 to 6.5 m around 2.5 to 6.5 m

Crane Height above crane rail top Crane Height above crane rail top around 4 to 6.5 m around 4 to 6.5 m

Allowance below roof over EOT :Allowance below roof over EOT :0.5m0.5m Total Height of the Power House Total Height of the Power House

Ht= H + ht of service bay+ ht Of unloading Ht= H + ht of service bay+ ht Of unloading largest package + crane ht & hook allowance largest package + crane ht & hook allowance + allowance below roof over EOT + margin + allowance below roof over EOT + margin


Height coefficient k

0.75 - 0.75

Height of Load bearing bracket Hj

=kxsqrt(Df)=1320

1300 1380 1340

Core Length Lc =1290 1520 3315.28 2860

Length of stator frame Lf

=Lc+1600=2890

3170 =Lc+1600=4915

3860

Distance between centre line of turbine and machine hall floor

=Hj+Lf+6000=10110

10170 =Hj+Lf+6000=12295

13900


Pelton wheel dimensionsWheel pitch diameter D2

2300 2330 3000 3020

Jet dia171 229.4 252 318

Outer wheel diamter

2900 3800

Number of Buckets (Approximate)

20 20 21 21

Suction head Hs

Hs = 1.87 + 2.24*Q/ns=2145

- 3442 -

To avoid discharge water splash

Hs>4*H1=2145>2400

- 3407 -

CL of Turbine wheel is set above TWL 2400

42003442 4000

Teesta III HEP

Malana II HEP

Selection of Turbines and Power House Dimesioning

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