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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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Characteristic of Weir Characteristic of Weir
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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Characteristic of Weir Characteristic of Weir
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
Lc Lw Ls
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
Design of E/M EquipmentDesign of E/M Equipment
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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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Design of E/M EquipmentDesign of E/M Equipment
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
DesignDesign of of E/M EquipmentE/M Equipment
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Design of E/M EquipmentDesign of E/M Equipment
CrossCross--Flow TurbineFlow Turbine
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DesignDesign of of E/M EquipmentE/M Equipment
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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DesignDesign of of E/M EquipmentE/M Equipment
Francis TurbineFrancis Turbine
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DesignDesign of of E/M EquipmentE/M Equipment
Reverse Pump Turbine (Pump as Turbine)Reverse Pump Turbine (Pump as Turbine)
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DesignDesign of of E/M EquipmentE/M Equipment
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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DesignDesign of of E/M EquipmentE/M Equipment
Tubular TurbineTubular Turbine
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Pico HydroPico Hydro
DesignDesign of of E/M EquipmentE/M Equipment
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DesignDesign of of E/M EquipmentE/M Equipment
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
DesignDesign of of E/M EquipmentE/M Equipment
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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 ( %)
DesignDesign of of E/M EquipmentE/M Equipment
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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)
DesignDesign of of E/M EquipmentE/M Equipment
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DesignDesign of of E/M EquipmentE/M Equipment
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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DesignDesign of of E/M EquipmentE/M Equipment
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:
DesignDesign of of E/M EquipmentE/M Equipment
• 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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DesignDesign of of E/M EquipmentE/M Equipment
• 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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DesignDesign of of E/M EquipmentE/M Equipment
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.