Dimensioning & Design of High Head Underground Hydroelectric Power Plant Superstructure

IJSTE - International Journal of Science Technology & Engineering | Volume 1 | Issue 11 | May 2015 ISSN (online): 2349-784X

All rights reserved by www.ijste.org

175

Dimensioning & Design of High head

Underground Hydroelectric Power Plant

Superstructure

Hardik R. Patel Prof. Zalakkumar R. Chhaya

P.G. Student Assistant Professor

Department of Civil Engineering Department of Civil Engineering

Merchant Institute of Technology Mehsana-384315,(Gujarat-

India)

L.D. College of Engineering, Ahmedabad-15(Gujarat-India)

Abstract

Hydroelectric power plant is a large structure comprises heavy structural mechanics itself. The whole plant is analysed as

Superstructure and Substructure. In this paper, preliminary dimensions of a high head and capacity power plant are computed as

per IS 12800, and from the computed dimensions structural modelling and design of super structure is carried out in Staad.Pro as

per IS 4247(Part I). An attempt is made to make calculations of dimensioning as per the codal provisions and design of

components of super structure using the software. Loadings and combinations are given as per the referenced IS codes including

Earthquake Static and Earth loads (for underground structures). The objective of the paper is to demonstrate procedure of fixing

dimensions and design of structure in Staad.Pro.

Keywords: Preliminary Dimensions, Superstructure, Underground Structure, Earthquake Loads

________________________________________________________________________________________________________

I. INTRODUCTION

Hydroelectric power plant consist super structure made of Heavy beams and columns with Steel roofing and Substructure with

massive concrete, in totality of almost around 50 to 60 m height. The first and essential part of any construction is the

dimensioning of components of power plant derived from the dimensions of functional components of it. Here hydroelectric

plant consist large equipments/Components mainly:

1) Heavy E.O.T. 2) Generator with stator and rotor 3) Turbine 4) Scroll case 5) Draft tube

IS 4247 is providing detailed guidelines of preliminary dimensioning of Power plant.

1) Roof 2) Roof supports 3) Gantry columns 4) Gantry girder 5) Beam or braces 6) Floors and

II. GROSS WATER HEAD, NET HEAD AND CAPACITY OF POWER PLANT

Gross Head: A.

It is a difference of head water level (u/s) and tail water level (d/s) when no water is flowing.

Net Head: B.

The head available for doing work on the turbine, that is, the difference between the total heads at inlet and outlet of turbine.

Dimensioning & Design of High head Underground Hydroelectric Power Plant Superstructure (IJSTE/ Volume 1 / Issue 11 / 028)


176

Capacity: C.

The capacity of a power plant is capacity of the total number of generators installed in a power plant. It depends on variation in

head, discharge, speed and efficiency for a turbine and speed, power factor and temperature rise in a generator.

III. PRELIMINARY DIMENTIONING OF POWER PLANT

Give Data:

Type of machine: Francis Turbine

Total number of machine: 6

Unit capacity:200 MW

Maximum Head : 120m

Rated Head :115 m

Minimum Head : 90 m

Barometric pressure at power house site :10 m

Vapour pressure at power house: 0.4 m

Power factor :0.9

Step 1: Synchronous Speed: A.

From Fig 1 IS 12800(part 1):1993 specific speed of machine may be taken as 190 r.p.m

Trial synchronous speed machine = ns x H^1.25 = 138

(p x 1.358)^0.5

Where

ns = 190 r.p.m

H = 115 m

P=200000 KW

Corrected specific speed =

=191 r.p.m

ns=176 r.p.m

H = 120 m

P=200000 KW

Step 2: Turbine Setting: B.

Where Hs =10 m

Hv=0.4 m

H- 120 m

=0.12 from fig 3 IS 12800(part 1): corresponding a specific speed of 191 r.p.m

With a further margin of 0.5 meters the center linr of the distributor should be set 4.8+0.5=5.3 meters below minimum tailrace

level

Step 3: Size of Runner: C.

Discharge diameter

=4.7 meters

Where

H=115 m

n = 191 r.p.m

ku=0.705 From fig 6 corresponding to a specific speed 191r.p.m

Step 4: Dimension of Spiral Case: D.

As the gross head above the turbine is more than 30 m metallic, spiral casing should be used .The main dimensions of the spiral

casing as determined in accordance with fig 8,9, and 10.



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A=1.13 X 4.7=5.32 m

B=1.40 X 4.7=5.21 m

C=1.50 X 4.7=5.58 m

D=1.67 X 4.7=7.88 m

E=1.27 X 4.7=5.99 m

F=1.65 X 4.7=7.88 m

G=1.40 X 4.7=6.63 m

H=1.22 X .7=5.78 m

Step 5: Size of Draft Tube: E.

As Determined in accordance with IS 5496-1969 Should be a below Height of draft tube at exit end h= 0.94 D3 to 1.32 D3

h.=1.25 x 4.7=5.88m

Depth of draft tube H for francis Turbine is 2.5 to 3.00 D3

Taking H1=2.75 x 4.7=12.92m

Length of draft tube L=4 to 5 D3

Taking L=4.5 x 4.7 =21.15 m

Cleat width B of the draft tube at exit end =2.6 to 3.3 D3

Taking B= 3 x 4.7=14.0 m

Since the cleat width of the draft tube is excessive a pier of 1.5 m width should be introduced in the center of the draft tube

.The total width of the draft tube will be 15.5 m

Discharge in cumecs

=197 cumecs

Where

P= 200000 Kw

H=115 m

= 0.9

Fig. 1:

Step 6: Generator Parameters: F.

Fig. 2: Generator Parameter

Air gap Diameter Dg



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Total no of pair of pole

Where f=50 and ns 191 r.p.m

From fig 15 taking Dg =10.02m

Outer diameter = 11 m

Where

Dg=10.42m P=16 no

Stator frame Diameter Df = Do+1.2 m

= 12.2 m

Inner Diameter of generator barrel Db= Dt+1.8

=12.2+1.8 =14 m

Core length of stator

=2.5 m

Where

W=200000/0.9= 222222

Ko=6.52 From fig 16

Dg=10.42 m

Length of stator frame Lt = Le+1.5=2.5+1.5=4m

Axial hydraulic thrust =292 tones Where

K=0.11 From fig 17

H max=120 m

Weight of generator rotor W=Le x rotar weight =701 tones

Where

Le=2.5 m

Rotar weight =280.5 tones/m from fig

Weight of turbine ruuner =36.3 from fig 19

Height of load bearing bracket h1=Total weight of rotating parts +Axial thrust

= 701+36.5+292

= 1029 tones

Height of load bearing bracket =

=2.97 m

Where

Suspended type of construction k=0.85

Dt =12.2 m

Step 7: Overall Dimension of Power Station: G.

Outer diameter of generator = inside diameter of generator + 2 x wall thick

=14+0.6+0.6=15.2 m

Width of Right side =7.6+2(from IS 12800-1993)=9.6m

Width of left side = 7.6+2+2=11.6 m

Total width of power station =11.6+9.6=21.2m

Length of erection bay=9.6+9.6=19.2m

Length of power station=6x 19.2+19.2+6=140.4 m

Height of machine at power station=H1+hj+Lt+k=12.92+2.97+4+6=25 .89m

IV. LOAD CALCULATION OF SUPERSTRUCTURE

Design A Steel Roof Truss For The Following Data: A.

Table - 1

Span of roof truss 21.2m

Spacing of roof truss 9.6m

Rise of truss 4m

Height of truss above the G.l 26m

Weight of purlin 90 N/m2

Total no of purlin each side 12



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1) Step 1: Preliminary Calculation: Angle of roof truss (): tan =4/10.6=0.37 =20.67

Length of P.R = = 11.11m

Half plan area=

x Spacing of R.T

=10.4 x 9.6

= 101.76 m2

Half slope area: length of P.R x Spacing of R.T

=11.11 X 9.6

=108.76 m2

2) Step 2: Dead load (D.l) :(Ref IS 875-1987 Part 1): Weight of roofing material:

For G.I sheets @ 130 N/m2 (on slope area)

W.t of roofing material =130 x108.76

= 14138.84 N

W.t of purlin= weight of purlin X Half plane area

=120 X 101.76

= 13228.8 N

Self-weight of Roof truss: [

]

=12279.04 N/m2

Weigh of wind bracing:

12n/m2 assume W.t of wind bracing =12 101.76 =1221.12 N

Total D.L = 40868.8 N

D.L per panel point=3.14 KN

3) Step 3 Live Load (Ref IS 875-1987 Part 2) L.L on purlin= 750-20(-10) N/m2 =750-20(20.67-10)

=536.6 >400 N/m2 O.K

L.L or R.T= 2/3 536.6=357.73 Total L.L=357.73 101.76 =36.402 kN

L.L on panel point=2.80 KNStep 3 Design of Purlin

Dead of purlin:

Weight of purlin=130 13 =1690 N

Self-weight of roofing material=

Length of each panel No of each side panel Self weight of purlin =0.87 13 130=1470.3 N Total Dead load =0.32 KN/m

Live load on purlin:

L.L on purlin=536.6 N/m2

Cos 20.67=x/0.87

X=0.81m

Plane Area of one panel=0.87 13 = 11.31m2

L.L on purlin= (0.87 13 536.5)=0. 63 KN/m

Design A Gantry Girder For The Following Data: B.

Crane capacity 200KN



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Span of gantry girder 21.2 m

Span of crane girder 9.6 m

Self W.T of crane girder exuding trolley 200KN

Self W.T of trolley crab 40KN

Minimum hook approach 1.2 KN

Wheel base of crane 3.5KN

Self W.T of rail section 300N/m

Take yield stress of steel 250 MPa

Fig. 3:

Maximum wheel load:

Crane capacity + W.T of trolley(crab)

=200+40

=240KN

Minimum hook approach=1.2m

Total weight of crane girder=200 KN

Weight of crane girder per m=

=9.43KN/m

Fig. 4:

Taking moment @ c

RD 21.2=240 1.2+9.43 21.2 10.6 RD=113.5 KN

Rc =Total load RD

=(240+9.43 21.2)-113.5 = 325.78 KN

At the each end of crane girder there are two wheels

Load on each wheel =

=162.89 KN



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Maximum B.M in the Gantry Girder (In Vertical Plane): 1)

Fig. 5:

Assume self-weight of gantry girder = 2 KN/m

Weight of rail section=0.3 KN/m

Total weight w=2.3 KN/m

Maximum B.M will occur a Taking moment @ A

= (163.20+163.20+3.92 4.6)-203.98 =144.45 KN RB 9.6= (163.20 3.925)+ (163.20 7.425)+(3.92 9.2 4.6) RB=203.98 KN

RA =Total load - RB

Taking Max reaction =203.98 KN

Superstructure Model in Staad.Pro and Its Results: C.

Fig. 6: Superstructure Model in Staad.pro

Fig. 7:



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Table 2 Beam No 13 Reinforcement Details

Horizontal Vertical Horizontal Moment

Node L/C Fx kN Fy kN Fz kN Mx kNm My kNm Mz kNm

Max Fx 506 6 EARTH PRESSURE 453.724 -12.254 -0.015 0.013 0.214 -691.68

Min Fx 632 6 EARTH PRESSURE -380.496 -72.077 -5.143 0 0 0

Max Fy 508 4 1.5DL+1.5L.L -120.342 2810.544 -2.336 -5.061 -0.228 223.21

Min Fy 13 7 EQZ 1.362 -196.259 -20.764 -104.433 -15.636 -3.023

Max Fz 44 16 1.5DL-1.5EQZ -8.44 2373.202 141.865 436.606 2.216 153.521

Min Fz 539 14 1.5DL+1.5EQZ -8.452 2373.235 -141.865 -436.605 -2.204 153.646

Max Mx 572 12 1.2DL+1.2LL-1.2EQZ -8.135 1219.005 68.306 871.067 9.669 320.168

Min Mx 11 10 1.2DL+1.2LL+1.2EQZ -8.105 1218.984 -68.306 -871.067 -9.706 319.898

Max My 11 6 EARTH PRESSURE 250.018 -12.5 0.746 -0.005 273.034 -680.465

Min My 572 6 EARTH PRESSURE 250.016 -12.5 -0.747 0.005 -273.038 -680.454

Max Mz 308 9 1.2DL+1.2LL+1.2EQX -127.512 2222.534 -0.081 -0.222 0.161 2172.917

Min Mz 275 19 0.9DL-1.5EQX 139.272 1393.542 0.052 0.132 0.216 -1889.73

Fig. 8:

Fig. 9:



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Table 3 Column No 12 Reinforcement Details

V. DISCUSSION

From the paper following can be discussed:

Analysis and design 1200Mw capacity hydroelectric power plant super structure was carried out using Staad.Pro

Dimensions of Plant are computed based on IS 12800(part 1) :1993

Base Shear due to EQ static loading is almost 3371 kN.

The modeling of super structure is carried out with guidelines of IS 4247 (part 1)-1998

REFERENCES

[1] Hydroelectric engineering By P.S.NIGAM [2] IS 1893:2002(part 1) Criteria for Earthquake resistant Design of structure Part 1: General provision and Building. [3] IS 800:1984 Code of Practice For General Construction In Steel [4] Guidelines for selection of turbine Preliminary dimensioning and layout of surface hydroelectric power house IS 12800(part 1) :1993 [5] Structural Design of surface Hydroelectric power station IS 4247(Part 1)-1993 [6] Code of practice for structural design of surface hydroelectric power station IS 4247(Part 2)-1992

Documents

Dimensioning & Design of High Head Underground Hydroelectric Power Plant Superstructure