tokyo electric power micro hydro

1

Workshop on Renewable EnergiesMarch 17, 2005

Majuro, Republic of the Marshall Islands

Module 4.3 Module 4.3 –– MicroMicro--HydroHydro

4.3.1 Designing 4.3.1 Designing Tokyo Electric Power Co. (TEPCO)

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ContentsContents

• Design for Civil Work

• Calculation of Head Loss

• Design of Electrical and Mechanical Equipment

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1. Selecting a Type of Intake Weir or Dam

(a) Concrete gravity dam(b) Floating concrete dam(c) Earth dam(d) Rockfill dam(e) Wet masonry dam(f) Gabion dam(g) Concrete reinforced gabion dam(h) Brushwood dam(i) Wooden dam(j) Wooden-frame dam with gravel

Design for Civil WorkDesign for Civil Worke7

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1-1.Concrete gravity dam

Concrete is used for the construction of the entire body.

• Foundation : Bedrock• River conditions : Not governed by gradient, discharge or level of

sediment load• Intake conditions: Good interception performance and intake

efficiency

Design for Civil WorkDesign for Civil Work

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1-2. Floating concrete dam

Lengthened infiltration path of the foundations by means of cut-off, etc. to improve the interception performance

•Foundations : In principle, gravel•River conditions : Not affected by the gradient, discharge or level of

sediment load•Intake conditions: Good interception performance and intake efficiency


Longer

Cut-off

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1-3. Earth dam

Earth is used as the main material for the body. The introduction of a riprap and core wall may be necessary depending on the situation.

•Foundations : Variable from earth to bedrock•River conditions : Gentle flow and easy to deal with flooding•Intake conditions: High interception performance and good intake

efficiency


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1-4. Rockfill dam

Gravel is used as the main material for the body. The introduction of a core wall may be necessary depending on the situation.

•Foundations : Various, from earth to bedrock•River Conditions : River where an earth dam could be washed away

by normal discharge•Intake conditions: Limited to the partial use of river water due to the

low intake efficiency


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1-5. Wet Masonry Dam

Filling of the spaces between gravel with mortar, etc.

•Foundations : Various, from earth to bedrock•River conditions : Not affected by the gradient, discharge or level of

sediment load•Intake conditions: Good interception performance and intake efficiency


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1-6. Gabion Dam

Gravel is wrapped in metal net to improve integrity.

•Foundations : Various, from earth to bedrock•River conditions : River where a rock-fill dam could be washed away

by normal discharge•Intake conditions: Limited to partial use of river water due to the low

intake efficiency


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1-7. Concrete Reinforced Gabion Dam

Reinforcement of the gabion surface with concrete

•Foundations : Various, from earth to bedrock •River conditions : River where the metal net could be damaged due to

strong flow•Intake conditions: Applicable when high intake efficiency is required


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1-8. Brushwood Dam

Simple weir using locally produced tree branches, etc.

•Foundations : Various, from earth to gravel layer•River conditions : Loss due to flooding is assumed•Intake conditions: At a site with a low intake volume or intake from a

stream to supplement the droughty water


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1-9. Wooden Dam

Weir using locally produced wood

•Foundations : Various, from earth to bedrock•River conditions : Relatively gentle flow with a low level of sediment

transport•Intake conditions: A certain level of intake efficiency is ensured with a

surface coating, etc.


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1-10. Wooden-Frame Dam with Gravel

The inside of the wooden frame is filled with gravel to increase stability.

•Foundations : Various, from earth to bedrock•River conditions : River at which a rock-fill dam could be washed away

by normal discharge•Intake conditions: Limited to the partial use of river water due to the

low intake efficiency


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Decision of weir height(1). Elevation of waterway considering:

- Geology, topography, existing structures, etc.

(2). Riverbed rise downstream

- Possibility of change of riverbed elevation

(3). Easy flushing sedimentation materials in front of intake

(4). Head acquisition and construction cost

(5). Backwater effect


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2. IntakeSide intake- Typical intake

- At right angles to the river

Tyrolean intake- Along the weir

- Simple structure

- Affected by sedimentation

during flooding

- More maintenance required

Side Intake

Tyrolean Intake

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3. Settling Basin

Function:•Settles and removes suspended materials of all sizes that could adversely affect the turbine.•Spills out excess water from spillway

Conduit sectionWidening section

Settling section

Bb

1.02.0

Dam

SpillwayStoplog Flushing gate

Intake

Headrace

Bsp

hs

hsp+

15cm

h0

10～

15ｃ

ｍ

hi

ic=1/20～1/30

IntakeStoplog

biＬｃＬｗＬｓ

Ｌ

Sediment Pit Flushing gate


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4. Headrace

Function:• Conveys water from the intake to the forebay• Spillways provided along the headrace for excess water

•Flow Capacity Qd = [ A ×R 2/3×SL

1/2 ] n

where,A: Cross-sectional areaR: R = A/PP: Length of wet sidesSL: Longitudinal slope of

headracen: Coefficient of roughness


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Simple earth channel Lined channel

(Rock and stone)

Wet masonry channel Concrete channel

n = 0.030n = 0.025

n = 0.020 n = 0.015

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n = 0.015

Wooded-fenced channel

Closed pipe (Hume pipe, steel pipe)

Box culvert channel

n = 0.015

n = 0.015, 0.012

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5. Forebay

Function:• Regulates fluctuating

discharge in the penstock and the headrace caused by load fluctuation.

• Has final function to remove materials (silt, sand), debris (leaves, trash, driftwood, etc.) in the water

Attached Structure:• Spillway• Screen• (Regulating gate)


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6. Penstock

• Conveys water under pressure from the forebay to the turbine• Materials: Steel, resin (Hard vinyl chloride, Howell, Fibre

Reinforced Plastics)• Diameter of pipe

d = C × (Qd／Vopt)0.5

where,


- ft- mDiameterd

3.38 to 9.2 ft3/s

1.0 to 2.8 m/s

Optimum velocity

Vopt

ft3/sm3/sDesigned discharge

Qd

2.3061.273CoefficientC

Imperial unitSI unit

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• Diameter of penstock affects output of a power plant.Increase of Diameter- Increase of Output

- Increase of CostOptimum Diameter to be determined

Output Limitation by Diameter of Penstock

0.010.020.030.040.050.060.070.080.090.0

100.0

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

Discharge (ft3/ s)

Out

put (

kW) D=10in

D=12inD=14inD=16inD=18in

Length of Penstock = 300ft, Coefficiency of Roughness = 0.013

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7. 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.


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a. Foundation for Impulse Turbine

The figures shows the foundation for the cross flow turbine. There is a space between the turbine and the surface of discharged water.

Flood W ater Level(M axim um )

20cm

boSection A -A

20cmb

bo: depends on Q d and H e

30～ 50cm

ｈｃ

30～ 50cm

H L3

(see Ref.5 -3)

hc={ }1/ 31 .1×Q d 2

9 .8×ｂ２

A

A

A fterbay T ailrace cannel O utle t


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Section A-A

1.5×d3

Flood Water Level(Maximum)30～50cmｈｃ

2× ｄ3

d3

20cm

1.15× d3

1.5×d3

Hs

Hs：depens on characteristic of turbine

HL3

(see Ref.5-3)

hc={ }1/ 31.1×Qd2

9.8×ｂ２

A

A

b. Foundation for Reaction Turbine

The below figures show the foundation for the Francis turbine. The outlet of the turbine is installed under the level of discharged water.

Pump

Gate

HL3

Flood Water Level (Maxmum)


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Calculation of Head LossCalculation of Head Loss

HgHHe

HL3

HL1

HL2

Intake

Settling Basin

Headrace

ForebayPenstock

Powerhouse

Tailrace

Head losses are indicated by the following figures at hydropowersystems. HL1 can be calculated easily as the differential water level between the intake to the forebay tank. Similarly HL3 can be calculated as the differential level between the center of the turbine to the tailrace.

He = Hg – (HL1 + HL2 + HL3)where, He: Effective head

Hg: Gross headHL1: Loss from intake to forebayHL2: Loss at penstockHL3: Installation head and loss at tailrace

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Calculation of Head LossCalculation of Head LossThe head loss at the penstock (HL2) can be calculated by the following equations.

HL2 = hf + he + hv + howhere,

hf: Frictional loss at penstockhe: Inlet losshv: Valve lossho: 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

hf = f × (Lp/Dp )× Vp2/2g

where, hf: Frictional loss at penstock (ft)f: Coefficient on the diameter of penstock pipe (Dp)

f = 185 × n2/Dp1/3

Lp: Length of penstock (ft)Vp: Velocity at penstock (ft/s)

Vp = Q/Apg: Acceleration due to gravitation (32.14 ft/s2)Dp: Diameter of penstock pipe (ft)n: Coefficient of roughness

(steel pipe: n = 0.012, plastic pipe: n = 0.011)Q: Design discharge (ft3/s)Ap: Cross sectional area of penstock pipe (ft2)

Ap = 3.14 × Dp2／4.0

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

he = fe × Vp2/2g

where, he: Inlet loss (ft)fe: Coefficient on the form at inlet.

Usually fe = 0.5 in micro-hydro scheme

(3) Valve Losshv = fv × Vp2 /2g

where, hv: Valve loss (ft)fv: Coefficient of the type of valve

fv = 0.1 ( butterfly valve)

(4) Others“Bend loss” and “loss on changes in cross-sectional area” are considered other losses. However these losses can be neglected in micro-hydro schemes. Usually, people planning micro-hydro schemes must take account of following margin for other losses.

ho = 5 to 10% × (hf + he +hv)

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<Reference > Head Loss at Penstock<Reference > Head Loss at PenstockIn SI Unit

(1) Frictional lossFrictional 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/Apg: 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

he = fe × Vp2/2g

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

Usually fe = 0.5 in micro-hydro schemes.

(3) Valve Losshv = fv × Vp2 /2g

where, hv: Valve loss (m)fv: Coefficient on the type of valve,

fv = 0.1 (butterfly valve)

(4) OthersBend 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)

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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. Turbine governor:Controls the speed and output of the turbine

4. Power transmission facility:Transmits the rotation power of the turbine to the generator.

5. Generator:Generates the electricity from the turbine or its transmitter.

6. Control panels:Controls and protects the above facilities for safe operation.

7. Switchgear (with transformer):Controls the electric power and increases the voltage of transmission

lines, if required

Note: Items 3, 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 Equipmente7

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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 velocity head through nozzles.

Reaction turbines: Rotates the runner by the pressure head.

Design for E/M EquipmentDesign for E/M Equipment

PropellerKaplan

FransisPump-as-Turbine

Reaction

CrossflowCrossflowTurgo

PeltonTurgo

ImpulseLowMediumHigh

HeadType

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1

10

100

1000

0.01 0.1 1 10 100Water Discharge

Effe

ctive

Hea

d

Design Design ofof E/M EquipmentE/M Equipment

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

Horizontal Horizontal 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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CrossCross--Flow TurbineFlow Turbine

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WaterWater

Guide VaneGuide VaneCrossCross--Flow W/TFlow W/T

Speed GovernorSpeed Governor

CrossCross--Flow TurbineFlow Turbinee7

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Francis TurbineFrancis Turbine

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Design Design of of E/M EquipmentE/M Equipment

Francis TurbineFrancis Turbinee7

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Tubular TurbineTubular Turbine

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GeneratorGenerator

Propeller RunnerPropeller RunnerGuide Vane Guide Vane (Wicket Gate)(Wicket Gate)

Timing BeltTiming BeltDraft Tube Draft Tube

Tubular TurbineTubular Turbinee7

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PeltonPelton TurbineTurbine

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PeltonPelton TurbineTurbinee7

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

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Pico HydroPico Hydro

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3. GeneratorSynchronous:

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

Asynchronous (induction):

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

Generator output: Pg (kVA) = (0.0847 x H x Q x η)/pfPg (kVA) = (9.8 x H x Q x η)/pf (in SI unit)

WherePg: output (kVA) H: Net head (ft, m)Q: Rated discharge (ft3/s, m3/s)η: Combined efficiency of turbine, transmitter & generator (%) pf: Power factor ( %). The value is based on the type of load in the system.


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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 (rpm) = 120 x f/P

where, P : Number of poles f : Frequency (HZ)

N0 : Rated rotation speed rpm)

For induction generators: N (rpm) = (1-S) x N0

where, N : Actual speed of induction generator (rpm) S : Slip (normally S= -0.02)N0 : Rated rotation speed rpm)

Design Design ofof E/M EquipmentE/M Equipmente7

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

– Gearbox type:The turbine shaft and generator shaft are coupled with helical 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% subject to 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% subject to 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 gear-type transmitter is very expensive.

Design Design of of E/M EquipmentE/M Equipment

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

(1) Mechanical type: Controls the water discharge constantly with the automatic operation of the guide vane(s) according to load. There are two types:

• Pressure-oil type• Motor type

Ancillary Equipment: Guide vane servomotor, pressure pump and tank, sump tank, piping or guide vane operated by electric motor


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(2) Dummy load type:To balance both the actual load and dummy load using a thyristor i.e. to keep the total of both the actual and dummy load constant for the same generator output and speed. The load is controlled by an electronic load controller (ELC).

The capacity of the 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 ExciterIn the case of a synchronous generator, an exciter is necessary for supplying field current to the generator and keeping the output voltage constant if the load fluctuates.

• Brush type: 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)

• Brushless type:The basic circuit consists of an AC exciter directly coupled to the main generator, a rotary rectifier and a separately provided automatic voltage regulator with a thyristor (AVR). (High initial cost but low maintenance cost)


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G

PT

CT

Ex. Tr

AVR PulseGenerator

Slip ring

(Speed Detector)

G

PT

CT

Ex. Tr

AVR

DC100V

PulseGenerator

Rotating section

ACEx

(Speed Detector)

5.2 Generator Exciter

Wiring diagram of exciter with brush Wiring diagram of brushless exciter


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5.3 Single Line Diagram

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

V

Hz

H

A x3

ELC (with Hz Relay)G

Turbine

Transmitterif required

Dummy Load

MagnetContactor

x3

NFB

Generator

V x3

Fuse

To Custmer

LampIndicator


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6.Control, Instrumentation and Plant Protection

6.1 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, single-person control and fully automatic control.

• The output control method is classified into output by single governor for independent network and water level control, discharge control and program control for parallel operation with another power source.


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6.2 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 is

recommended to check and summarize total energy produced by the power plant


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6.3 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-voltage4. Over-current by NFB (No Fuse Breaker) or MCCB (Molded Case Circuit

Breaker) for low-tension circuits.

When items 1, 2 and 3 are detected by an ELC (with screw adjustment), the magnet contactor (MC) is activated and trips the main circuit of the generator.


tokyo electric power micro hydro

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