Designing Micro Hydro

Module 4.3 Micro-Hydro

4.3.1 Designing Tokyo Electric Power Co. (TEPCO)

Workshop on Renewable Energies November 14-25, 2005 Nadi, Republic of the Fiji Islands

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Contents 

Design (Civil Structure) 

s e i g r e n E e l b a w e n e R n o p o h s k r o W A P P / 7 e

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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Civil Structure: Weir Types of Weir     


    

Concrete gravity dam Floating concrete dam Earth dam Rockfi Rockfillll dam Wet masonry dam Gabion dam Concrete reinforced gabion dam Brushwood dam Wooden dam Wooden-frame Wooden-frame dam with gravel

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Characteristic Characterist ic of Weir Characteristic Type

Outline


Concrete gravity dam Entire body is composed of concrete.

Floating concrete dam Entire body is composed of concrete. Longer dam epron cut-off

Foundation

Bedrock

Gravel

River condition

Not governed by gradient, discharge or level of sediment load

Not governed by gradient, discharge or level of sediment load

Intake efficiency

High

High

Concrete gravity dam

Floating concrete dam

Earth dam Main material is earth. Riprap and core wall

From earth to bedrock Gentle flow and easy to deal with flooding High

Earth dam

Cut-off

Longer epron

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Characteristic Characterist ic of Weir Characteristic

Outline


Rock fill dam

Type

Wet masonry dam

Main material is gravel. Core wall

Gabion dam

Gravel is filled with mortal etc.

Gravel is wrapped by metal net.

Foundation

From earth to bedrock



River condition

In case that earth dam could be washed away by normal river flow.

Not governed by gradient, discharge or level of sediment load.

In case that rock fill dam could be washed away by normal river flow.

Intake efficiency

Low

High

Low

Rock fill dam

Wet masonry dam

Gabion dam

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Characteristic Characterist ic of Weir Characteristic Type Outline Foundation River condition


Intake efficiency

Concrete reinforced gabion dam

Bush wood dam

Surface of gabion dam is reinforced with concrete. From earth to bedrock In case that metal net could be damaged by strong river flow. High

Concrete reinforced gabion dam

Wooden frame with gravel dam

Main material is local bush wood.

Wooden frame is filled with gravel.

From earth to bedrock Gentle river flow

Fair

Bush wood dam

From earth to bedrock In case that rock fill dam could be washed away by normal river flow. Low

Wooden frame with gravel dam

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Concerns to be addressed in Weir Designing 



Location of weir site 

Perpendicular to river direction



Topographical & geological conditions



Easy access

Structural Stability 






Sedimentation 

Easy flushing



Existing landslide, debris, erosion, drift woods etc.

Influence on head acquisition 



Fall resistance, Sliding resistance & Soil bearing capacity against resultant external force (weir own weight, water pressure, sedimentation weight, earth quake & up lift)

Relationship between construction cost & usable head

Backwater effect 

Influence on upstream area during flooding 7

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Civil Structure: Intake Type of Intake 

 s e i g r e n E e l b a w e n e R n o p o h s k r o W A P P / 7 e

Side intake 

Typical intake



Perpendicular Perpendicular to river direction

Tyrolean intake 

Along the weir



Simple structure



Affected by sedimentation during flooding



More maintenance required

Side Intake

Tyrolean Intake 8

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Civil Structure: Settling Basin Function 

All the suspended materials that could adversary affect turbine should be removed. Dam Intake

Specification to be decided

Spillway

Stoplog

Flushing gate




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 & wide

B

b

Headrace

1.0

Conduit section

2.0

Settling section Widening section

Bsp

ｃ

m c 5 1 + p s h

5 1

～Intake

0 1

hi

Stoplog

h0 hs

ic=1/20～1/30

Sediment Pit

Ｌｃ bi

Ｌｗ

Flushing gate

ＬｓＬ

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Civil structure: Headrace Function 

Conveys water from intake to forebay

Specification to be decided 

Structure type (Open channel) Longitudinal slope slope (1/50 – 1/500)  Longitudinal  Cross section (flow capacity)  Material to be used s e i g r e n E e l b a w e n e R n o p o h s k r o W A P P / 7 e

Flow capacity calculation Qd=A× =A×R2/3×SL1/2 ／n where, Qd: Flow capacity (design discharge: m3/s ) A: Cross-sectiona Cross-sectionall area R: R = A/P P: Length of wet sides A SL: Longitudinal slope n: Coefficient of roughness

P

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Characteristic of Headrace Simple earth channel

Type

Advantage


Disadvantage

Lined channel (Rock & stone)

Wet masonry channel

Concrete channel



Easy construction Inexpensive  Easy repair



Easy construction Local material  Scouring resistance  Easy repair





Local material Scouring resistance  Applicable to permeable ground  Easy construction















Risk of scouring & collapse  Not applicable to high permeable ground  Difficult to remove sedimentation

n = 0.030

Not applicable to high permeable ground

Relatively expensive More man power

Not applicable to small diameter  Long construction period

n = 0.020

n = 0.025

Simple earth channel



Lined channel (Rock and stone)

Great flexibility of cross section design

n = 0.015

Wet masonry channel

Concrete channel 11

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Characteristic of Headrace Wood fenced channel

Type  

Advantage

Inexpensive Flexible to minor ground deformation



Disadvantage s e i g r e n E e l b a w e n e R n o p o h s k r o W A P P / 7 e

Not applicable to big diameter  Easy to decay

n = 0.015

Wooded-fenced channel

Box culvert channel

Hume pipe channel



Easy construction Short construction period  Applicable to small diameter  Flexible to cross section figure













Heavy weight High transportation cost

n = 0.015

Box culvert channel

Easy construction Short construction period  High resistance to external pressure  Applicable to small diameter 

Heavy weight High transportation cost

n = 0.015

Closed pipe (Hume pipe, steel pipe)

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Civil Structure: Forebay Function 



Regulates discharge fluctuation difference between penstock & headrace due to load fluctuation. Final settling basin

Screen

Spillway

Specification to be decided  s e i g r e n E e l b a w e n e R n o p o h s k r o W A P P / 7 e



Water storage capacity Layout & dimension of each facility

Attached Structure    

Spillway Screen Regulating gate Sluice gate

Headrace

Spillway Penstock Headrace

Screen Headrace

Penstock

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Civil Structure: Penstock Function 

Convey water under pressure from forebay forebay to turbin turbine e

Specification to be decided 


Route (Slope, geological conditions etc)  Material to be used  Diameter - Const Construc ructi tion on cost cost - Electricity Electricity generation generation decrease decrease due due to loss at penstock - Durability Durability (Life time, O&M cost) 

Thickness - Water pressure, pressure, own own weight, weight, water weight, other external force (earth quake etc.)

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Powerhouse

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Powerhouse 

Function: Provides shelter for the electro-mechanical electro-mechanical equipment 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 -Pelton turbine, turbine, Turgo Turgo turbine turbine or cross-flow cross-flow turbine, turbine, etc. etc. •For Reaction turbine -Francis turbine or propeller turbine, etc. 15

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Foundation for Impulse Turbine a. Foundation for Impulse Turbine The figures shows the foundation foundation for the cross flow turbine. There is a space space between between center level of the runner runner and the tailwater tailwater level

A

2

hc={


30 ～ 5 0 c m

1.1×Qd 9.8× ２

}

1/ 3

Flood Water Level(Maximum)

ｈ

Space (atmosphere pressure)

H L3 (see Ref.5-3) 30 ～ 5 0 c m

A Afterbay

T a ilil ra ra ce ce c an an ne ne l

O u tltl et et

Section A-A bo

20cm

b o : d e p e n d s o n Q d a n d H e

20cm b

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Foundation for Reaction Turbine 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 A

d3

ThisHs：head is also also effectively utilized depens on characteristic of turbine 2

hc={


1.1×Qd 9.8× ２

1/3

}

Hs

Filled with water

m c 0 2

30 ～ 50cm ｈｃ

Flood Water Level(Maximum)

1.15× d3

In the draft tube

H L3 (see Ref.5)

2× ｄ3 1.5×d3

A

Section A-A

1.5×d3

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Effective Head Effective

Head (Net head) :

= The total head 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 Intake

Headrace HL1

Settling Basin

HL2

Forebay Penstock

H Hg Powerhouse

He

HL3 Tailrace

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Calculation of Head Loss The head loss at the penstock (HL2) can be calculated by the following equations. ho 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 crosssectional area and others)

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Head Loss at Penstock (1) Fricti Frictiona onall loss loss Frictional loss (hf) is the biggest of the losses at penstock. hf = f ×(Lp/ (Lp/Dp Dp ) ×Vp2 /2g /2g where,


hf: Frictional loss at penstock (m) f : Coefficient on the diameter of penstock pipe pipe (Dp). 2 1/3 f = 124.5× 124.5×n /Dp Lp: Length of penstock (m) Vp: Velocity at penstock (m/s) Vp = Q/Ap Q/Ap g: Acceleration due to gravity (9.8m/sec (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 (m 2) Ap = 3.14 3.14×Dp2/4.0 20

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Head Loss at Penstock (2) (2) Inle Inlett Loss Loss hi = fe × Vp2/2g wher where, e,

hi: hi: Inle Inlett loss loss (m) (m) fe: Coefficient on the form at the inlet Usually fe = 0.5 in micro-hydro schemes. schemes.

(3) (3) Valv Valve e Loss Loss hv = fv fv × Vp2 /2g s e i g r e n E e l b a w e n e R n o p o h s k r o W A P P / 7 e

wher where, e,

hv: hv: Valv Valve e loss loss (m) (m) fv: Coefficient on the type of valve, fv = 0.1 (butterfly valve)

(4) (4) Oth Others ers Bend loss and loss due to changes in cross-sectional area are considered other losses. However, these losses can be neglected in micro-hydro schemes. Usually, the person planning the micro-hydro scheme must take account of following margins as other losses. ho = 5 to 10%× (hf + he +hv) +hv) 21

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Design of E/M Equipment Equipment and Functions 1. Inle Inlett val valve ve:: 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 combined in one panel.

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Design of E/M Equipment

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1. Inlet Valve


23

Design for E/M Equipment

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2. Water Turbine Types: 




Impulse turbines: Rotates the runner by the impulse of water jets by converting the pressure head into the t he velocity head through nozzles. Reaction turbines: Rotates the runner by the pressure head. Type Impulse

Reaction

Head High

Medium

Low

Pelton Turgo

Crossflow Turgo

Crossflow

Fransis Pump-as-Turbine

Propeller Kaplan

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Design of E/M Equipment Pelton Turbine Acting

water jet emitted from the nozzle to the bucket of runner

Good

characteristics for discharge change - Discha Discharge rge:: Small Small (0.2 (0.2 – 3 m3/s) - Head: Head: High High head head (75 (75 – 400m) 400m)


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Design of E/M Equipment Pelton Turbine


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Design of E/M Equipment Cross-Flow Turbine Arc

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

Easy

manufacturing and simple structure - Discha Discharge rge:: Small Small (0.1 (0.1 – 10 m3/s) - Head Head:: Low Low,, midd middle le head head (2 – 200 200 m) m)


Water Cross-Flow W/T

Guide Vane 27

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Design of E/M Equipment Cross-Flow Turbine


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Design of E/M Equipment Francis Turbine Turbine Wide

ranging utilization from various head and output

Simple structure

- Discharge Discharge:: Various Various (0.4 – 20 m3/s) - Head: Head: Low Low to high high (15 (15 – 300 m) m)


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Design of E/M Equipment Francis Turbine Turbine


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Design of E/M Equipment Reverse Pump Turbine (Pump as Turbine)


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Design of E/M Equipment Tubular Turbine Tubular

type(Cylinder type) propeller turbine

Package

type is remarked recently - Discharge Discharge:: Various Various (1.5 – 40 m3/s) - Head: Head: low low head head (3 (3 – 20m) 20m)


Timing Belt

Guide Vane (Wicket Gate)

Generator Draft Tube

Propeller Runner 32

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Design of E/M Equipment Tubular Turbine


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Design of E/M Equipment Pico Hydro


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Design of E/M Equipment Flow chart of designing hydro turbine Power plant H,Q Number of units


Turbine type selection by the selection chart

Ns limit

Pelton

8 – 25

Francis

50 – 350

Diagonal flow

100 – 350

Propeller

200 – 900

Tubular

N limit calculation from the Ns limit

N

Range of Ns (m-kW)

Turbine type

More than 500

Specific speed:

P1/2 Ns[m-kW] = N × H5/4

(min-1) 35

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Design of E/M Equipment Selection of turbine type

i.e.: H = 25m, Q = 0.45m3/s (82ft)

(15.88ft3 /s)

Cross Flow

1000

(3,280)

or Horizontal Francis

(m, ft ft))

Horizontal Pelton


d 100 a (328) e H e v i t c e f f E

10

Vertical Francis

Cross Flow

(32.8)

Horizontal Francis (3.28)

1 0.01 (0.3529)

Horizontal Propeller 0.1 (3.529)

1 (35.29) Water Dischar e

10 (352.9)

(m3/s,

ft3/s /s))

100 (3,529)

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Design of E/M Equipment 3. Generator Synchronous:





Asynchronous (induction):






Independent exciter rotor, applicable for both isolated and existing power networks

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

Generator output:

Pg (kVA) = (9.8 x H x Q x η)/pf

Where Pg: Capacity (kVA) H : Net head head (m) Q: Rated discharge (m3/s) η: Combined efficiency efficiency of turbine & generator etc (%) pf: Power factor ( %)

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Design of E/M Equipment 3. Generator 

Speed and Number of Generator Poles - The rated rotational speed speed is specified according according to to the frequency frequency (50 or 60 Hz) of the t he 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 poles f : 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) 38

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Design of E/M Equipment 

Standard rated speeds and number of poles for synchronous generators No. of poles

50 Hz

60 Hz

4

1500

1800

6

1000

1200

8

750

900

10

600

720

12

500

600

14

429

514

16

375

450

18

333

400

20

300

360

24

250

300


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Comparative table of synchronous and induction generators Structure


Synchronous generators

Induction generators

Operation

Parallel-in operation

•Excitation circuit •Relatively large air gap

•Voltage regulation •Reactive power adjustment (Usually lagging power factor)

•Synchronizer •Less electromechanical impact at parallelin

•No excitation •High maintainability •High rotational speed

• No voltage voltage regulation •Leading power factor operation •Only on-grid operation

•No synchronizer •Inrush current (Parallel-in around synchronous speed is preferable.)

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Design of E/M Equipment 4. Driving Facility (Speed Increaser) To match the speed of the turbine and generator –


–

Gearbox ty 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 depending on the type of 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. 41

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Design of E/M Equipment 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 speed fluctuates if there are 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: • PressurePressure-oil oil type • Motor Motor type type Ancillary Equipment: Servomotor, pressure pump and tank, sump tank, piping or electric motor for gate operating mechanism

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Design of E/M Equipment (2) Dummy load type: Generator output is always constant at a micro hydro power station where a dummy 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.

Customers of Electricity

Transformer

Upper Dam

Spillway

Upper Reservoir Po we we r Ho us use Dummy Load Governor

G-T

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The capacity of dummy load is calculated as follows: Pd (kW) = Pg (kVA) x pf (decimal) x SF where, Pd: Pd: Pg: pf: SF:

Capaci pacity ty of dum dummy my load load (Uni (Unity ty load load:: kW) kW) Rated output of generator (kVA) Rated power factor of generator Safety factor according to cooling method (1.2 – 1.4 times generator output in kW) to avoid over-heating the heater 44

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Design of E/M Equipment 5.2 Generator Generator Exciter Exciter In the case of a synchronous generator, an exciter is necessary for supplying field current to the generator and keeps the terminal voltage constant even though the load fluctuates. The type of exciter is classified as follows: • DC exci excite ter: r: A DC generator directory coupled with main shaft supplies field current of the synchronous generator. The generator terminal voltage is regulated by adjusting the output voltage of DC exciter. exciter. Maintenance Maintenance on brushes, commutato commutatorr is necessary.

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Design of E/M Equipment • AC exciter: The excitation circuit consists of an AC exciter directly coupled to the main CT generator, a rotary rectifier and a separately provided automatic voltage regulator with a thyristor thyristor (AVR). (AVR). (High (High initial cost but low maintenance cost)

PT Pulse Generator

AVR

S eedDe eedDetecto tector r

Ex. Tr

Rotating section DC100V G

AC Ex

Brushless exciter

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Design of E/M Equipment • Sta Static tic exci excita tati tion on:: Direct thyristor excitation method. DC current for the field coil is supplied through a slip ring from a thyristor with an excitation transformer. (Low initial cost but high maintenance cost)

PT Pulse Generat Generator or

AVR

CT

(Speed Detector)

Ex. Tr

Slip ring

G

Static excitation

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Design of E/M Equipment 6. Switchgears Single Line Diagram: The typical single diagram diagram for a 380/220V distribution distribution line Magnet Contactor


A x3

x3 Lamp Indicator

V V

Hz

Turbine

H

G Transmitter

ELC (with Hz Relay)

NFB

Fuse

To Custmer

x3

Dummy Load

Generator

if required

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Design of E/M Equipment Switchgear board including ELC

CB(MCCB)


ELC

NFB

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Design of E/M Equipment 7. Control Panels 7.1 Control Methods:


• Superviso Supervisory ry control control method method is is classifie classified d into contin continuous uous supervisory, remote continuous control and occasional control. • The operati operational onal control control method method is is classified classified into into manual manual control, control, one-man control and fully automatic control. • The output output control control method method is classi classified fied into into dummy dummy load govern governor or control for isolated grid, discharge control, water level control and programmable programmable control.

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Design of E/M Equipment 7.2 Instrumentation • Pressu Pressure re gauge gauge for pensto penstock ck • Voltmeter Voltmeter with with chang change-ove e-overr switch switch for for output output voltage voltage • Voltmeter Voltmeter with with changechange-over over switch switch for output output of of dummy dummy load (ballast) • Ammeter Ammeter with chang change-ove e-overr switch switch for ampere ampere of generato generatorr output output • Frequenc Frequency y meter meter for rotati rotational onal speed speed of genera generator tor • Hour Hour meter meter for operat operating ing time time • kWh kWh (kW (kW hour) hour) meter meter and and kVh kVh (kVar (kVar hour) hour) meter, meter, which which are are required to summarize and check total energy generation at the power plant

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Design of E/M Equipment 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-spee Over-speed d of turbine and and generator generator (detected (detected by frequency) frequency) 2. Unde Underr-vo volt ltag age e 3. Ov Over er-v -vol olta tage ge 4. Over-curr Over-current ent by NFB (No Fuse Breaker) Breaker) or MCCB MCCB (Molded Case Case Circuit 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 wide of the rotational rotational speed speed range range will be applica applicable ble for the selected turbine when the turbine efficiency is 0.6?

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Answer There is a potential site with the following f ollowing 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, Horizo Horizontal ntal Propel Propeller, ler, and and Horizonta Horizontall Francis (Please refer to the selection chart.) Q2: How wide of the applicable range of specific speed on a selected turbine? A2: If the horizon horizontal tal propelle propellerr is selected, selected, the range range of of Ns is 200 – 900 (m-k (m-kW). W).

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Selection of turbine type 1000

(3,280)

(m, ft ft))

Horizontal Pelton d 100 a (328) e H e v i t c e f f E


Vertical Francis

Cross Flow

10

(32.8)

Horizontal Francis (3.28)

1 0.01 (0.3529)

Horizontal Propeller 0.1 (3.529)

1 (35.29) Water Discharge

10 (352.9)

(m3/s,

ft3/s /s))

100 (3,529)

55

) 1 0 : 2 1 ( 5 0 v o N 1



Answer Q3: How wide wide of the rotational rotational speed speed range range will be applica applicable ble for the selected turbine when the turbine efficiency is 0.6? A3: The tur turbin bine e outp output ut P is 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. 56

Designing Micro Hydro

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