designing micro hydro

8/7/2019 Designing Micro Hydro

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Workshop on Renewable Energies

November 14-25, 2005

Nadi, Republic of the Fiji Islands

Module 4.3 MicroModule 4.3 Micro--HydroHydro

4.3.1 Designing4.3.1 Designing

Tokyo Electric Power Co. (TEPCO)

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ContentsContents

Design (Civil Structure) Weir, Intake, Settling basin, Headrace, Forebay, Penstock,

Powerhouse

Head Loss Calculation

Design (Electrical and Mechanical Equipment) Inlet valve, Water turbine, Turbine governor, Power

transmission facility, Generator, Control panels, Switchgear



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Types of Weir

Concrete gravity dam Floating concrete dam

Earth dam

Rockfill dam

Wet masonry dam

Gabion dam

Concrete reinforced gabion dam

Brushwood dam

Wooden dam

Wooden-frame dam with gravel

Civil Structure: Weir Civil Structure: Weir

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Characteristic of Weir Characteristic of Weir

HighHighHighIntake efficiency

Gentle flow and easy todeal with flooding

Not governed by gradient,

discharge or level of sediment load

Not governed by gradient,

discharge or level of sediment load

River condition

From earth to bedrockGravelBedrockFoundation

Main material is earth.

Riprap and core wall

Entire body is composed

of concrete.

Longer dam epron

cut-off

Entire body is composed

of concrete.Outline

Earth damFloating concrete damConcrete gravity damType

Longer epron

Cut-off

Concrete gravity dam Floating concrete dam Earth dam



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LowHighLowIntake efficiency

In case that rock fill damcould be washed away by

normal river flow.

Not governed by gradient,discharge or level of

sediment load.

In case that earth damcould be washed away by

normal river flow.

River condition

From earth to bedrockFrom earth to bedrockFrom earth to bedrockFoundation

Gravel is wrapped by

metal net.

Gravel is filled with mortal

etc.

Main material is gravel.

Core wallOutline

Gabion damWet masonry damRock fill damType

Rock fill dam Wet masonry dam Gabion dam

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LowFair HighIntake efficiency

In case that rock fill dam

could be washed away bynormal river flow.

Gentle river flowIn case that metal net

could be damaged bystrong river flow.

River condition

From earth to bedrockFrom earth to bedrockFrom earth to bedrockFoundation

Wooden frame is filled

with gravel.

Main material is local

bush wood.

Surface of gabion dam is

reinforced with concrete.Outline

Wooden frame with graveldam

Bush wood damConcrete reinforcedgabion dam

Type

Concrete reinforced gabion dam Bush wood dam Wooden frame with gravel dam



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Location of weir site

Perpendicular to river direction

Topographical & geological conditions

Easy access

Structural Stability

Fall resistance, Sliding resistance & Soil bearing capacity against resultantexternal force (weir own weight, water pressure, sedimentation weight, earthquake & up lift)

Sedimentation

Easy flushing

Existing landslide, debris, erosion, drift woods etc.

Influence on head acquisition

Relationship between construction cost & usable head

Backwater effect

Influence on upstream area during flooding

Concerns to be addressed in Weir DesigningConcerns to be addressed in Weir Designing

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Civil Structure: IntakeCivil Structure: Intake

Type of Intake

Side intake

Typical intake

Perpendicular to river direction

Tyrolean intake

Along the weir

Simple structure

Affected by sedimentationduring flooding

More maintenance required

Side Intake

Tyrolean Intake



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Function All the suspended materials that could

adversary affect turbine should be removed.

Specification to be decided Minimum diameter of suspended materials

(depend on turbine specification; 0.5–

1.0mm)

Marginal settling speed (about 0.1m/s)

Flow velocity in settling basin (about 0.3m/s)

Length & wideConduit section

Widening sectionSettling section

B b

1.0

2.0

Dam

SpillwayStoplog Flushing gate

Intake

Headrace

Bsp

hs

h s p + 1 5 c m

h0

1 0 ～ 1 5 ｃ

hi

ic=1/20～

1/30

IntakeStoplog

bi

ＬｃＬｗＬｓ

Ｌ

Sediment PitFlushing gate

Civil Structure: Settling BasinCivil Structure: Settling Basin

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Function Conveys water from intake to forebay

Specification to be decided Structure type (Open channel)

Longitudinal slope (1/50 – 1/500)

Cross section (flow capacity)

Material to be used

Flow capacity calculation

Qd=A×R2/3×SL1/2 ／nwhere,

Qd: Flow capacity (design discharge: m3/s )

A: Cross-sectional area

R: R = A/P

P: Length of wet sides

SL: Longitudinal slope

n: Coefficient of roughness

Civil structure: HeadraceCivil structure: Headrace

PA



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Characteristic of HeadraceCharacteristic of Headrace

Risk of scouring &collapse

Not applicable tohigh permeableground

Difficult to removesedimentation

Easy construction Inexpensive

Easy repair

Simple earth

channel

Not applicable tosmall diameter

Long constructionperiod

Relatively expensive

More man power Not applicable to

high permeableground

Disadvantage

Great flexibility of cross sectiondesign

Local material Scouring resistance

Applicable topermeable ground

Easy construction

Easy construction Local material

Scouring resistance

Easy repair Advantage

Concrete channelWet masonry

channel

Lined channel

(Rock & stone)Type

Simple earthchannel

Lined channel(Rock and stone)

Wet masonrychannel

Concrete channel

n = 0.030 n = 0.025 n = 0.020 n = 0.015

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Characteristic of HeadraceCharacteristic of Headrace

Not applicable to bigdiameter

Easy to decay

Inexpensive

Flexible to minor grounddeformation

Wood fenced channel

Heavy weight

High transportation cost

Heavy weight

High transportation costDisadvantage

Easy construction

Short construction period

High resistance to external

pressure

Applicable to small diameter

Easy construction

Short construction period

Applicable to small diameter

Flexible to cross sectionfigure

Advantage

Hume pipe channelBox culvert channelType

n = 0.015

Wooded-fenced channel Closed pipe (Hume pipe, steel pipe)Box culvert channel

n = 0.015n = 0.015



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Powerhouse

Function:

Provides shelter for the electro-mechanical equipment (turbine,generator, control panels, etc.)

The size of the powerhouse and the layout:

Determined taking into account convenience during installation,operation and maintenance.

Foundation:

Classified into two:•For Impulse turbine

-Pelton turbine, Turgo turbine or cross-flow turbine, etc.

•For Reaction turbine

-Francis turbine or propeller turbine, etc.

PowerhousePowerhouse

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a. Foundation for Impulse Turbine

The figures shows the foundation for the cross flow turbine. There

is a space between center level of the runner and the tailwater level

Flood Water Level(Maximum)

20cm

boSection A-A

20cm

b

bo: depends on Qd and He

30 ～ 50cm

ｈ

30 ～ 50cm

H L3

(see Ref.5-3)

hc={ }1/ 31.1×Qd

2

9.8× ２

A

A

Afterbay T a il ra ce c an ne l O u tl et

Foundation for Impulse TurbineFoundation for Impulse Turbine

Space

(atmosphere pressure)



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Section A-A

1.5×d3

Flood Water Level(Maximum)30～50cm

ｈｃ

2× ｄ3

d3

2 0 c m

1.15× d3

1.5×d3

Hs

Hs：depens on characteristic of turbine

HL3

(see Ref.5-

)

hc={ }1/31.1×Qd

2

9.8× ２

A

A

b. Foundation for Reaction Turbine

The below figures show the foundation for the Francis turbine. The

outlet level of the draft tube is under the level of tailwater

Foundation for Reaction TurbineFoundation for Reaction Turbine

Filled with water

In the draft tube

This head is also effectively utilized

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Effective HeadEffective Head

HgHHe

HL3

HL1

HL2

Intake

Settling Basin

Headrace

Forebay

Penstock

Powerhouse

Tailrace

Effective Head (Net head) := The total head actually acting on the turbine

= Gross head – Head loss

He = Hg – (HL1 + HL2 + HL3)

where, He: Effective head

Hg: Gross head

HL1: Loss from intake to forebay

HL2: Loss at penstock

HL3

: Loss at tailrace and draft tube



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Calculation of Head LossCalculation of Head Loss

The head loss at the penstock (HL2) can be calculated bythe following equations.

HL2 = hf + he + hv + ho

where,

hf: Frictional loss at penstock

he: Inlet loss

hv: Valve loss

ho: Other losses (Bend losses, loss on changes in cross-

sectional area and others)

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<Reference > Head Loss at Penstock<Reference > Head Loss at Penstock(1) Frictional loss

Frictional loss (hf) is the biggest of the losses at penstock.

hf = f ×(Lp/Dp ) ×Vp2 /2g

where, hf: Frictional loss at penstock (m)

f : Coefficient on the diameter of penstock pipe (Dp).

f = 124.5×n2/Dp1/3

Lp: Length of penstock (m)

Vp: Velocity at penstock (m/s)

Vp = Q/Ap

g: Acceleration due to gravity (9.8m/sec2)

Dp: Diameter of penstock pipe (m)

n : Coefficient of roughness

(steel pipe: n = 0.012, plastic pipe: n = 0.011)

Q: Design discharge (m3/s)

Ap: Cross sectional area of penstock pipe (m2)

Ap = 3.14×Dp2/4.0



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<Reference > Head Loss at Penstock<Reference > Head Loss at Penstock(2) Inlet Loss

hi = fe × Vp2/2g

where, hi: Inlet loss (m)fe: Coefficient on the form at the inlet

Usually fe = 0.5 in micro-hydro schemes.

(3) Valve Loss

hv = fv × Vp2 /2g

where, hv: Valve loss (m)

fv: Coefficient on the type of valve,

fv = 0.1 (butterfly valve)

(4) Others

Bend loss and loss due to changes in cross-sectional area are considered

other losses. However, these losses can be neglected in micro-hydroschemes. Usually, the person planning the micro-hydro scheme must takeaccount of following margins as other losses.

ho = 5 to 10%× (hf + he +hv)

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Equipment and Functions

1. Inlet valve:

Controls the supply of water from the penstock to the turbine

2. Water turbine:

Converts the water energy into rotating power

3. Generator:

Generates the electricity by the driving force from the turbine

4. Driving facility:

Transmits the rotation power of the turbine to the generator

5. Control facility of turbine and generator:Controls the speed, output of the unit.

6. Switchgear / transformer :

Controls the electric power and increases the voltage of transmission

lines, if required

7. Control panels:

Controls and protects the above facilities for safe operation.

Note: Items 5, 6 & 7 above may sometimes be combined in one panel.

Design of E/M EquipmentDesign of E/M Equipment



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1. Inlet Valve


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2. Water Turbine

Types:

Impulse turbines: Rotates the runner by the impulse of water jetsby converting the pressure head into the velocity head throughnozzles.

Reaction turbines: Rotates the runner by the pressure head.

Design for E/M EquipmentDesign for E/M Equipment

Propeller

Kaplan

Fransis

Pump-as-Turbine

Reaction

CrossflowCrossflow

Turgo

Pelton

Turgo

Impulse

LowMediumHigh

HeadType



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PeltonPelton TurbineTurbineActing water jet emitted from the nozzle to the bucket of runner

Good characteristics for discharge change

- Discharge: Small (0.2 – 3 m3/s)

- Head: High head (75 – 400m)

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DesignDesign of of E/M EquipmentE/M Equipment

PeltonPelton TurbineTurbine



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Arc shape runner blades are welded on the both side of iron plate discs

Easy manufacturing and simple structure

- Discharge: Small (0.1 – 10 m3/s)

- Head: Low, middle head (2 – 200 m)

WaterWater

Guide VaneGuide Vane

CrossCross--Flow W/TFlow W/T

CrossCross--Flow TurbineFlow Turbine


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CrossCross--Flow TurbineFlow Turbine



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Francis TurbineFrancis TurbineWide ranging utilization from various head and output

Simple structure

- Discharge: Various (0.4 – 20 m3/s)

- Head: Low to high (15 – 300 m)

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Francis TurbineFrancis Turbine



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Reverse Pump Turbine (Pump as Turbine)Reverse Pump Turbine (Pump as Turbine)

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GeneratorGenerator

Propeller RunnerPropeller RunnerGuide VaneGuide Vane

(Wicket Gate)(Wicket Gate)

Timing BeltTiming Belt

Draft TubeDraft Tube

Tubular TurbineTubular TurbineTubular type(Cylinder type) propeller turbine

Package type is remarked recently

- Discharge: Various (1.5 – 40 m3/s)

- Head: low head (3 – 20m)



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Tubular TurbineTubular Turbine

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Pico HydroPico Hydro




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Flow chart of designing hydro turbineFlow chart of designing hydro turbine

Power plant H,Q

Number of units

Turbine type selection by

the selection chart

Ns limit

N limit calculation from the

Ns limit

N (min-1)

More than 500Tubular

200 – 900Propeller

100 – 350Diagonal flow

50 – 350Francis

8 – 25Pelton

Range of Ns

(m-kW)Turbine type

Ns[m-kW] = N ×5/4

1/2

H

P

Specific speed:

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1

10

100

1000

0.01 0.1 1 10 100

Water Dischar e

E f f e c t i v e H e a d

Selection of turbine type i.e.:i.e.: H = 25m, Q = 0.45mH = 25m, Q = 0.45m33/s/s

→ Cross FlowCross Flow

oror Horizontal FrancisHorizontal Francis

Horizontal FrancisHorizontal Francis

Cross FlowCross Flow

HorizontalHorizontal PeltonPelton

Horizontal PropellerHorizontal Propeller

(m3/s, ft3/s)

(m, ft)

(3,529)(352.9)(35.29)(3.529)(0.3529)

(3.28)

(3,280)

(32.8)

(328)

(82ft) (15.88ft3 /s)

Vertical FrancisVertical Francis




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3. Generator

Synchronous:

Independent exciter rotor, applicable for both isolated and existingpower networks

Asynchronous (induction):

No exciter rotor is usually applicable in networks with other power sources. In isolated networks, it must be connected to capacitors togenerate electricity.

Generator output: Pg (kVA) = (9.8 x H x Q x η)/pf

Where

Pg: Capacity (kVA)

H : Net head (m)

Q: Rated discharge (m3/s)

η: Combined efficiency of turbine & generator etc (%)

pf: Power factor ( %)


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3. Generator

Speed and Number of Generator Poles

- The rated rotational speed is specified according to the frequency

(50 or 60 Hz) of the power network and the number of poles by

the following formula:

For synchronous generators:

P (nos.) = 120 x f/N0 N0 (min-1) = 120 x f/P

where, P : Number of polesf : Frequency (Hz)

N0 : Rated rotational speed (min-1)

For induction generators:

N (min-1) = (1-S) x N0

where, N : Actual speed of induction generator (min-

1)

S : Slip (normally S= -0.02)

N0 : Rated rotational speed (min-1)




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Standard rated speeds and number of poles for synchronous

generators

30025024

36030020

40033318

45037516

51442914

60050012

72060010

9007508

120010006

180015004

60 Hz50 HzNo. of poles

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Comparative table of synchronous and induction generators

•No synchronizer

•Inrush current

(Parallel-in around

synchronous

speed is

preferable.)

•No voltage

regulation

•Leading power

factor operation

•Only on-grid

operation

•No excitation

•High

maintainability

•High rotational

speed

Induction

generators

•Synchronizer

•Less electro-

mechanical

impact at parallel-

in

•Voltage

regulation

•Reactive power

adjustment

(Usually lagging

power factor)

•Excitation

circuit

•Relatively large

air gapSynchronous

generators

Parallel-in

operationOperationStructure



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4. Driving Facility (Speed Increaser)To match the speed of the turbine and generator

– Gearbox type:

The turbine shaft and generator shaft are coupled with gears

with parallel shafts in one box with anti-friction bearings

according to the speed ratio between the turbine and generator.

The life is long but the cost is relatively high. (Efficiency: 95 –

97%, depending on the type)

– Belt type:

The turbine shaft and generator shaft are coupled with pulleys

or flywheels and belts according to the speed ratio between the

turbine and generator. The cost is relatively low but the life is

short. (Efficiency: 95 – 98%, depending on the type of belt)

In the case of a micro hydro-power plant, a V-belt or flat belt type

coupling is usually adopted to save the cost because the gearbox

type transmitter is very expensive.


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5. Control Facility of Turbine and Generator

5.1 Speed Governor:

The speed governor is adopted to keep the turbine speed constant

because the speed fluctuates if there are changes in the load, water head or flow.

(1) Mechanical/Electrical type:

Controls the turbine speed constantly by regulating the guide vanes /

needle vanes according to load. There are two types of power source:

• Pressure-oil type

• Motor type

Ancillary Equipment:

Servomotor, pressure pump and tank, sump tank,

piping or electric motor for gate operating mechanism




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(2) Dummy load type:

Generator output is always

constant at a micro hydro

power station where adummy load governor is

applied to. In order to keep

the frequency constant, the

relationship “generator

output = customers load +

dummy load” is essential.

The dummy load is controlled

by an electronic load

controller (ELC) to meet the

above equation.

Transformer Customers of Electricity

Dummy Load Governor

Spillway

Upper Reservoir

G-T

Upper Dam

Power House


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The capacity of dummy load is calculated as follows:

Pd (kW) = Pg (kVA) x pf (decimal) x SF

where,

Pd: Capacity of dummy load (Unity load: kW)

Pg: Rated output of generator (kVA)

pf: Rated power factor of generator

SF: Safety factor according to cooling method (1.2 – 1.4 times

generator output in kW) to avoid over-heating the heater




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5.2 Generator Exciter

In the case of a synchronous generator, an exciter isnecessary for supplying field current to the generator and keeps the terminal voltage constant even thoughthe load fluctuates. The type of exciter is classified asfollows:


• DC exciter:

A DC generator directory coupled with main shaftsupplies field current of the synchronousgenerator. The generator terminal voltage isregulated by adjusting the output voltage of DCexciter. Maintenance on brushes, commutator is

necessary.

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DesignDesign of of E/M EquipmentE/M Equipment• AC exciter:

The excitation circuitconsists of an ACexciter directlycoupled to the maingenerator, a rotaryrectifier and aseparately provided

automatic voltageregulator with athyristor (AVR). (Highinitial cost but lowmaintenance cost)

G

PT

CT

Ex. Tr

AVR

DC100V

Pulse

Generator

Rotating section

AC

Ex

S eedDetector

Brushless exciter



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• Static excitation:

Direct thyristor

excitation method.DC current for thefield coil is suppliedthrough a slip ringfrom a thyristor with an excitationtransformer. (Lowinitial cost but highmaintenance cost)

G

PT

CT

Ex. Tr

AVRPulse

Generator

Slip ring

(Speed Detector)

Static excitation

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6. Switchgears

Single Line Diagram:

The typical single diagram for a 380/220V distribution line

V

Hz

H

A x3

ELC(with Hz Relay)G

Turbine

Transmitter

if required

Dummy Load

Magnet

Contactor

x3

NFB

Generator

Vx3

Fuse

To Custmer Lamp

Indicator




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NFB

CB(MCCB)

Switchgear board including ELC

ELC


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7. Control Panels

7.1 Control Methods:

• Supervisory control method is classified into continuous

supervisory, remote continuous control and occasional control.

• The operational control method is classified into manual control,

one-man control and fully automatic control.

• The output control method is classified into dummy load governor control for isolated grid, discharge control, water level control and

programmable control.




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7.2 Instrumentation

• Pressure gauge for penstock• Voltmeter with change-over switch for output voltage

• Voltmeter with change-over switch for output of dummy load

(ballast)

• Ammeter with change-over switch for ampere of generator output

• Frequency meter for rotational speed of generator

• Hour meter for operating time

• kWh (kW hour) meter and kVh (kVar hour) meter, which are

required to summarize and check total energy generation at thepower plant


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7.3 Protection of Plant and 380/220V Distribution Line

Considering the same reason for cost saving in instrumentation, the following

minimal protection is required for micro-hydro power plants in rural

electrification.

1. Over-speed of turbine and generator (detected by frequency)

2. Under-voltage

3. Over-voltage

4. Over-current by NFB (No Fuse Breaker) or MCCB (Molded Case Circuit

Breaker) for low-tension circuits.

When an item 1, 2 or 3 is detected, the protective relay is activated and forces

the main circuit breaker trip. At that time, the unit shall be stopped to check

conditions.




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Exercise

There is a potential site with the following conditions:

Net head: 10 m

Discharge: 1 m3/s

Frequency: 50 Hz

Synchronous generator is required.

Q1: Which types of turbine are preferable for the site?

Q2: How wide of the applicable range of specific speed on

a selected turbine?

Q3: How wide of the rotational speed range will be applicable for

the selected turbine when the turbine efficiency is 0.6?

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DesignDesign of of E/M EquipmentE/M Equipment Answer

There is a potential site with the following conditions:

Net head: 10 (m)

Discharge: 1 (m3/s)

Frequency: 50 (Hz)

Synchronous generator is required.

Q1: Which types of turbine are preferable for the site?

A1: Cross Flow, Horizontal Propeller, and Horizontal

Francis

(Please refer to the selection chart.)

Q2: How wide of the applicable range of specific speed on

a selected turbine?

A2: If the horizontal propeller is selected, the range of Ns is

200 – 900 (m-kW).



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1

10

100

1000

0.01 0.1 1 10 100

Water Discharge

E f f e c t i v e H e a d

Selection of turbine type

Horizontal FrancisHorizontal Francis

Cross FlowCross Flow

HorizontalHorizontal PeltonPelton

Horizontal PropellerHorizontal Propeller

(m3/s, ft3/s)

(m, ft)

(3,529)(352.9)(35.29)(3.529)(0.3529)

(3.28)

(3,280)

(32.8)

(328)

Vertical FrancisVertical Francis


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DesignDesign of of E/M EquipmentE/M Equipment Answer

Q3: How wide of the rotational speed range will be applicable for

the selected turbine when the turbine efficiency is 0.6?

A3: The turbine output P is

P = 9.8 ηt Q H = 9.8 × 0.6 × 1 × 10 = 58.8 (kW)

so that the minimum and maximum rotational speeds are

calculated as follows:

Nmin = Nsmin × H5/4 / P1/2

= 200 × 105/4 / 58.81/2

= 463 (min-1)

Nmax = 900 × 105/4 / 58.81/2

= 2087 (min-1)

Considering the standard rated speed, the speed range from

500 to 1500 (min-1) is applicable for the direct coupled

generator.

In case that 500 (min-1) is selected as the turbine rated speed

considering turbine characteristics, a speed increaser is

preferable to apply because lower speed generators are costly.

designing micro hydro

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