Electro Mechanical Aspects

of

Micro Hydro & Small Hydro

Surendra Mathema

President, NMHDA

100KW Barpak Micro Hydro

Power from Hydro

Total efficiency, η = ηp x ηt x ηd x ng

Where ,

ηp = penstock efficiency

ηt = turbine efficiency

ηd = drive mechanism efficiency

ηg = generator efficiency

Power (KW) = 9.81 x H (m) x Q (lit/sec) x η

1000

Turbine Type

The turbines are main equipment for converting hydraulic power to the shaft power (mechanical power).

By principle of operation there two types of turbine

A. Reaction Turbine• Francis Turbine (Medium head & medium discharge)

• Kaplan Turbine (Low head & high discharge)

B. Impulse Turbine• Pelton Turbine (High head & low discharge)

• Turgo Turbine (Medium head & medium discharge)

• Cross Flow Turbine (Low to medium head & low discharge)

Turbine Selection Monogram

Turbine Selection Monogram

Turbine SpeedThe relationship between specific speed and turbine speed is as follows

Where Ns = Specific speed

N = Turbine speed (RPM)

Hd = Design head of turbine in meter

P = Turbine power in KW

If direct drive is required, synchronous speed of generator should be the turbine speed.

Synchronous speed of generator for 50 Hz

12 pole – 500 RPM 10 pole – 600 RPM

8 pole – 750 RPM 6 pole – 1000 RPM

4 pole – 1500 RPM 2 pole - 3000 RPM

Ns = N x P0.5

Hd 1.25

Specific Speed & Head Range for

Different Turbine

S.N Turbine type Range of specific

speed

Range of head Range of runaway

speed, rpm

1 Kaplan 300 – 1000 4 m to 40 m 2.0 to 2.2 x normal speed

2 Francis 50 – 450 30 m to 450 m 1.9 to 2.2 x normal speed

3 Pelton 10 – 70 100m to 2000m 1.8 to 1.9 x normal speed

4 Cross-flow 20 – 70 5m to 200m 1.8 to 2.0 x normal speed

5 Turgo 20 – 80 30 m to 300m 1.9 to 2.0 x normal speed

General Efficiency of Different Turbine

Turbine type General efficiency trend Best efficiency

Kaplan Good efficiency range for full and part load

condition and can be operated up to 20% load

0.91

Francis Full load efficiency is good and part load efficiency

is poor and not recommends operating below 50%

load

0.92 to 0.94

Pelton Good efficiency range for full and part load

condition and can be operated up to 30% load

0.90

Cross-flow Good efficiency range for full and part load

condition and can be operated up to 30% load

0.80

Turgo Good efficiency range for full and part load

condition and can be operated up to 25% load

0.85

Kaplan Turbine

Fixed Runner of Kaplan Turbine

Variable Pitch Kaplan Runner

Kaplan Turbine

Francis Turbine Runner

Francis Turbine Runner

Francis Turbine

Francis Turbine Model

Francis Turbine

Pelton Turbine

Pelton Turbine

Pelton Turbine from bottom

Pelton Turbine from Canyon

Turgo Turbine

Turgo Turbine

Turgo Turbine

Turgo Turbine

Turgo Turbine at Tatopani Small Hydro

Cross Flow Turbine

Cross Flow Turbine

Cross Flow Turbine

70 KW Cross Flow Turbine, Bhutan

Cross Flow Turbine

Cross Flow Turbine

Valve & Shutdown Mechanism For

Turbine

Valve are mechanical devices that control the flow

to the piping systems. The inlet valves are used

to shut off flow to the turbine.

The most common type of valves are

a)Butterfly valves (used up to 250m water head)

b)Spherical valves (used for high head application)

Electric driven shutdown valve

Shutdown Mechanism Jet Deflector

for Pelton Turbine

Pelton Turbine with shut down system

100KW Pelton at Bhutan with jet

deflector

Breaking mechanism to stop the

Turbine

Direct drive with tire coupling

Gear Drive System

General Parameter of Synchronous

Generator• Rated output …. kVA

• Power factor 0.8

• Frequency 50 Hz

• No. Of phases 3

• Rated terminal voltage between phases …. kV

• Range of voltage variation between phases for rated

output ± 10%

• Range of frequency variation ± 5%

• Stator winding connection star connection

• Speed …. RPM

• Short circuit ratio not less than 0.8

• Inertia constant not less than 1.0

• Generator efficiency not less than 96%

• Generator cooling open cooling

Generator Derating Factor

Maximum ambient

temperature (Co)

20 25 30 35 40 45 50 55

A Temperature

Factor

1.1 1.08 1.06 1.03 1 0.96 0.92 0.88

Altitudes (m) 1000 1250 1500 1750 2000 2250 2500 2750

B Altitude factor 1 0.98 0.96 0.945 0.93 0.915 0.9 0.88

Altitudes (m) 3000 3250 3500 3750 4000 4250 4500 4750

B Altitude factor 0.86 0.845 0.83 0.815 0.8 0.785 0.77

C Power Factor 0.8

Generator Voltage, Speed

Excitation System

• The operating voltage of the generator increase with power. For hydro generator in the range of 100 KW to1000 KW, the standard generation voltages of 400 V, 690 V,3300 V can be used.

• In general the speed of the generator should be matched with turbine speed; if not speed matching should be used.

• Normally self excited self regulated excitation should be used

Flow Control Governor

Digital Controller of Flow Contol

Governor

PLC based Governor Controller

Hydraulic Governor controlled by PLC

Woodward Hydraulic Governor

PLC control of Small Hydro, Baramchi

ELC, Synchronizing & Load Panel for

Bhutan

Panel under test before dispatch

Governor

Governor

Transformers

• Generator Transformeri. Type 3 phase, oil immersed

ii. Installation outdoor

iii. Rated capacity …. kVA

iv. Rated H.V. (secondary) ….kV

v. Rated L.V. (Primary) ….kV

vi. Cooling ONAN

vii. Rated frequency 50Hz

viii. Primary Connection Delta

ix. Secondary Connection Star

x. Efficiency not less than 98%

xi. Grounding primary - ungrounded

secondary - solid

• Station Transformer

Switchgear equipment

Turbine Protection

i. Bearing temperature extremely high/low

ii. Failure of governor

iii. Over speed

iv. Oil level of pressure oil tank low or high

v. Regulating pond/reservoir water level below the

setting etc.

Generator Protection

i. Differential protection (>500 KW)

ii. Field loss protection (only if grid)

iii. Reserve power protection (only if grid)

iv. Negative sequence over current protection

v. Over voltage and over current protection

vi. Ground over current protection and earth fault protection

vii. Out of synchronization protection

Transformer Protection

i. Differential protection

ii. Over current and earth fault protection

iii. Oil temperature indicator with alarm

iv. Buchholz relay with alarm and trip control (>500

KW)

v. Winding temperature indicator with alarm and

trip control

vi. Oil gauge with low - level alarm

Feeder Protection

i. Three phase over current

ii. Earth fault protection (suited to local supply

system)

DC Power System

Power station require a DC system with a battery

charger, station batteries and a DC distribution

panel for control, protection, emergency

lighting, communication system etc. 110V DC or

48V DC system should be adopted. A battery

charger suitable to maintain boost and float

charging for the above battery shall be installed.

Over Head Crane

Namaste and wish you nice time in

Nepal