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THUNAG MINI HYDRO PROJECT 400KW
1
Developer:- Tek Singh Rathore
CHAPTER-VII
ELECTRICAL & MECHANICAL
DESIGN M
General
Thunag MHEP utilizes the flow of Debla nallah tributary of Beas river and is located in
Distt-Mandi of Himachal Pradesh. A net head of 118.56m has been utilized which generates
400 KW of power at surface power house.
The salient features of Thunag MHEP are as under:-
* Net head : 118.56 m
* Installed Capacity : 400 KW
* Number and size of units: : 400KW ( one unit)
* Type of power house : Surface
* Design discharge of plant : 0.40 cumecs
* Turbine type : Horizontal Francis
* Speed of turbine : 500rpm
* Generation voltage : 0.415KV
* Transmission voltage : 11KV
* Step-Up Transformer : 600KVA
7.1 POWER HOUSE
In a Mini hydropower scheme the role of the powerhouse is to protect the electromechanical
equipment that convert the potential energy of water into electricity. The number, type and
power of the turbo-generators, their configuration, the scheme head and the geomorphology
of the site determine the shape and size of the building.
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Developer:- Tek Singh Rathore
In Thunag MHEP, the surface of power house will have a generating unit of 400KW along
with all auxiliary facilities such as cooling water/potable water supply system, fire protection
system, compressed air supply, oil system, ventilation and air conditioning system etc.
The control room, LT room, battery room, offices, cable spreading area will be
accommodated in different floors adjacent and parallel to the machine hall, the service bay
shall be located at one end of the machine hall. The generator transformer will be located in
the switchyard located up stream of the machine hall and will be connected to generating
units through 11KV bus ducts.
MEDIUM AND HIGH HEAD SCHEME
In medium and high head schemes, powerhouses are more conventional with an entrance for
the penstock and a tailrace. Although not usual, this kind of powerhouse can be underground.
THUNAG MINI HYDRO PROJECT 400KW
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Developer:- Tek Singh Rathore
The following equipment will be displayed in the powerhouse:
• Inlet gate or valve
• Turbine
• Speed increaser (if needed)
• Generator
• Control system
• Condenser, switchgear
• Protection systems
• DC emergency supply
• Power and current transformers
7.2 TURBINE
Particulars of Hydro Turbine
S.N. Technical Particulars Specifications/Parameters
1. Type of Turbine/Shaft orientation Horizontal Francis
2. No. of unit 1
3. Output
a. Rated output at rated net head 400 Kw
b. Max. Output at rated net head 480 Kw
4. Efficiency 90%
5. Speed
a. Rated speed in r.p.m. 500 rpm
b. Maximum runaway speed in r.p.m. 900 rpm
c. Direction of rotation when viewed from
generator end/top.
Clockwise
THUNAG MINI HYDRO PROJECT 400KW
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Developer:- Tek Singh Rathore
General
The maximum gross head is 124.81 m. Total head losses in the penstock corresponding to
design discharge of 0.40 Cumecs mainly comprises of frictional losses. Net head works out
to 118.56. Alternatives of installing single unit of appropriate capacity have been examined.
The provision of one units appear advantageous and has been proposed. Therefore, one
number turbines are proposed to fulfill the following design requirements
A mini hydropower scheme converts hydro potential energy into mechanical energy and
then to electrical energy. Energy is power delivered in unit time.
Output power = P
Turbine output power (kW) = ȠT × ȠG x Q× g ×H
Where: ȠT - Efficiency of turbine (90 %)
ȠG-Efficiency of generator (95%)
g - Gravity (9.81 m2/s)
H net - Net head available at the turbine (118.56 m)
Q - Water volume enters into turbine per second (0.40 m3/s)
Turbine output power (kW) = 0.90x0.95x0.40x9.81x118.56
=397.87KW, say 0.40MW
Therefore, out power of unit = 400 = 400 kW
Specific speed
It is the speed in revolution per minute at which the given turbine would rotate, if reduced
homologically in size so that it would develop unit power under unit head at full gate.
Low specific speeds are associated with high heads and high specific speed is
associated with low heads. The selection of a high specific speed for a given head will
result in a smaller turbine and generator with saving in capital cost. However the turbine
will have to be placed lower for which the cost may offset the saving.
Also at high specific speed lower efficiency is expected.
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Developer:- Tek Singh Rathore
Specific speed is given by the formula.
n√P
Ns = -------------
H (5/4)
Where:
Ns = Specific speed in r.p.m
η = Speed of turbine in r.p.m
P = output power of turbine in KW
H = Net head in meter
A set of curves showing specific speed versus head of Francis, propeller, and Francis
turbines are shown in Fig. given below. Curves for cavitation coefficient σ for francis and
Kaplan turbines are also shown in the same figure.
Assuming Francis Turbine
n = 375
Ns = (375x√400)/118.565/4
= 19.17
Assuming Francis Turbine
n = 500
Ns = (500x√400)/118.565/4
= 25.56
Assuming Francis Turbine
n = 750
Ns = (750x√400)/118.565/4
= 38.34
Assuming Francis Turbine
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Developer:- Tek Singh Rathore
n = 1000
Ns = (1000x√400)/118.565/4
= 51.12
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Developer:- Tek Singh Rathore
The ranges of specific speed for various types of turbines are given below:
Type of runner Specific speed (Ns)
(i)Impulse Francis/Turgo = 12-70
(ii)Cross flow = 20-80
(iii)Reaction Francis = 80-400
(iv)Propeller and Kaplan = 340-1000
On the basis of above data we can considered Francis turbine for this project. Due to
small capacity of the unit it would be economical and beneficial to install Francis Turbine
with speed of 500rpm and specific speed is 25.56rpm, at Thunag MHEP, as higher the
speed of turbine lesser will be the cost of Generator.
One number of horizontal Francis turbines each 400 KW 90% of efficiency was used in
order to increase the part flow efficiency, increase reliability and easiness in overhauling
the turbines without shutdown the plant.
Effective head was same for both units. But flow was shared equally and subsequently
output power was divided equally.
7.2 Generator
Particulars of GENERATOR
Sl. No. Description.
1. Type. Synchronous
2. Rated output in kw 400 kW
3. Continuous Over Load Capacity. 10%
4. Power Factor. 0.85
5. Shaft orientation. Horizontal
6. Speed.
a. Rated Speed. 500 RPM.
b. Runaway Speed. 900 RPM.
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Developer:- Tek Singh Rathore
(i) Type of Generator
Generators transform mechanical energy into electrical energy. Although most early
hydroelectric systems were of the direct current variety to match early commercial
electrical systems. Now days only three-phase alternating current generators are used in
normal practice.
• Synchronous generators: They are equipped with a DC electric or permanent magnet
excitation system (rotating or static) associated with a voltage regulator to control the
output voltage before the generator is connected to the grid. They supply the reactive
energy required by the power system when the generator is connected to the grid.
Synchronous generators can run isolated from the grid and produce power since
excitation is not grid-dependent .
(ii) Class of insulation
Present practice is to specify class F insulation system for the stator and rotor winding
with class B temperature rise over the ambient. Ambient temperature rise should be
determined carefully from the temperature of the cooling water etc.
Accordingly maximum temperature for the insulation class under site conditions should
be specified.
a) Stator:
Class F insulation level and Class B temperature rises are recommended.
b) Rotor:
The insulation level should normally be Class-F and temperature raises Class-B.
(iv) Type of cooling
Losses in a generator appear as heat which is dissipated through radiation and ventilation.
The generator rotor is normally constructed to function as an axial flow blower, or is
equipped with fan blades, to circulate air through the windings. Small-generators up to 5
MW may be partially enclosed, and heated generator air is discharged into the generator
hall, or ducted to the outside.
Adequate ventilation of the generator hall preferably thermostatically should be provided
in this case.
THUNAG MINI HYDRO PROJECT 400KW
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Developer:- Tek Singh Rathore
Water to air coolers normally is provided for all modern hydro generators rated greater
than 5MW. The coolers are situated around the outside periphery of the stator core.
Normally, generators should be furnished with one cooler than the number required for
operation at rated MVA. This allows one cooler to be removed for maintenance without
affecting the unit output.
(v) Generator inertia
The moment of Inertia of the generator together with the moment of inertia of the turbine
shall be such that the maximum momentary speed rise under Governor Control on full
load rejection shall not exceed 45% of rated speed for the grid connected generator as
station power is supplied from main generator and adverse effect of this speed rise on
motor driven station auxiliaries is not desirable. Additional flywheel required shall be
built in the rotor. Separate flywheel shall not be permitted.
(vi) Starting method
The starting method used in Thunag MHEP should be in Manual and Auto both mode.
7.3 Generator-transformer connections
The power shall be generated at 0.415 kv which is economical voltage for generators in
the capacity range 0.5-2.5MW and also in view of transportation weight limitation. Unit
system layout of the generating unit shall be adopted at the power station. The generating
units will be connected through 0.415/11kv step up transformers to the outdoor 11 kv bus
bar. The electrical scheme proposed for the power station and the switch yard is shown in
the single line diagram.
7.4 Transformer
The generator step up and auxiliary power supply transformers shall be installed in the
switchyard of the power station. The detail of transformers is given below:
Generator step up
Transformer
Station auxiliary
suppply Transformer
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Developer:- Tek Singh Rathore
Voltage ratio 0.415/11 kv 11/0.415 kv
Rated capacity 600 KVA 75KVA
No of transformers 1 1
Voltage range ±10% ±10%
Cooling type ONAN ONAN
Rated Frequency 50 Hz 50 Hz
Frequency variation ± 3% ± 3%
7.5 Switchyard equipment
Switchyard consists following equipments:-
(a) 11 KV circuit Breaker
(b) 11 KV C/R Panel
(c) 11 KV Isolator without Earth switch
(d) 11 KV CTs
(e) 11 KV/110V PTs
(f) 11KV LAs
(g) 11 KV Isolator with Earth switch
7.6 Single line scheme
Single line scheme is shown in the SLD Drawing.
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Developer:- Tek Singh Rathore
7.7 Control & protection equipment
Controls of Switchgear Panel,Protection Panel & Power
Transformer
1
TG control,Relay,Metering cum PLC based Governor
panel
ANSI Protection
21 Under Impedance relay
24 Over fluxing relay
27/59 Voltage protection relay
32 Reverse power relay
37 Under power relay
40 Field failure relay
46 Negative sequence relay
49 Thermal overload protection
50/27 Unintentional energisation of standstill
50V/51V Voltage controlled over current
51BF Breaker failure relay
60FL VT fuse failure
64S Stator earth fault relay
81 Under frequency relay
87G Generator differential relay
86B Electrical Action Shutdown
86C Control Action Shutdown
86E Emergency Action Shutdown
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Developer:- Tek Singh Rathore
2
1.1 KV Breaker panel
ANSI Protection
86 Master Trip relay
94 Trip circuit supervision relay
64B Bus Earth fault relay
3
Transformer cum Line Relay metering and protection
panel
ANSI Protection
67 Directional overcurrent relay
67N Directional Earthfault relay
27 Undervoltage rerlay
59 Overvoltage relay
64REF Resticted Earth fault relay
86L Master Trip relay for Line
87T Transformer Differential relay
4
Line Relay metering cum protection panel(Receiving
End)
ANSI Protection
67 Directional overcurrent relay
67N Directional Earthfault relay
27 Undervoltage rerlay
59 Overvoltage relay
86L Master Trip relay for Line
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Developer:- Tek Singh Rathore
5
LTAC panel(415V)
ANSI Protection
50 Overcurrent relay
51N Earth fault relay
6
Power Transformer Accessories
ANSI Protection
WTI Winding Temperature Indicator
OTI Oil Temperature Indicator
BZ Bucholz relay
MOG Magnetic oil level gauge
(A) GOVERNORS
Governing system shall be complete with actuator unit comprising of speed response
element, restoring mechanism having adjustable temporary and permanent drop setting, load
limiting device and speed level control. The oil pressure system will comprise of sump tank
and an oil pressure oil tank and one electrically operated governor oil pumps, one with
normal running and other acting as stand by unit shall be provided.
Governor shall be suitable for selected turbines. In the event of any abnormal operation,
generator will be isolated from main line and turbine will be stopped by closing inlet/gate
valve. Over current and earth fault protection are provided on H.T switch gear and
transformers, against voltage surges lightening arrestor will be provided. All electrical
equipment in the power house and switch yard area will be protected, grounded and rubber
mats will be used wherever necessary in order to protect the workers from electric shock.
All electrical equipment in power house and switch yard area will be properly insulated
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Developer:- Tek Singh Rathore
wherever necessary in order to protect the workers from electric shock, noncurrent carrying
parts of all equipment will be connected to earth net.
(B) ELECTRICAL MASTER CONNECTIONS AND CONTROL
Electrical master connections are composed of generators, transformers, circuit breakers,
current and voltage transformers, including conductor between them for generation,
transmission and distribution of electrical energy. Electrical master connections are
proposed to fulfill the following essential requirements:-
(i) To ensure quality and reliable supply of electrical energy as per the requirement of power
grid and consumers.
(ii) To achieve economy and low investment on Maintenance and Operation.
(iii) To ensure reliability and flexibility in operation.
(iv) To ensure convenience in maintenance.
A central control panel will be provided from where all functions of the generating units,
transformers and lines etc. will be controlled.
The generators manufacturer shall be asked to supply all equipment and devices for control
instrumentation and safety relating to the generators. These together with equipment
supplied by the turbine manufacturer shall constitute a complete and coordinated set of
instruments, control and safety devices for the control of these units during normal running
and in an emergency.
The AVR shall control the voltage within the limits specified. The AVR shall have a
provision for operation in both power factor and voltage control mode. The AVR shall
also have a manual channel supplied independently of the auto channel and proper follow
up to facilitate the switching between auto and manual channels. The AVR shall have
provision for quadrate droop compensation for stable operation. The control/indication
and power handling components though housed in the same cabinet shall be suitably
isolated.
The AVR shall also have following features:-
- Under/Over Excitation protection.
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- Maximum/Minimum excitation limiters.
- Grid paralleling features.
(C) EMERGENCY CONTROL AND PROTECTION
Emergency control shall be provided to protect the equipment and auxiliary system during
emergency. Control board and H.T. gear panel will be provided for each turbine generator
set so that all functions of machine are monitored and controlled. The 110V DC supply will
be provided for emergency lights, indicators and control equipment.
Over voltage, restricted earth fault, over speed, over current, under voltage and speed action
equipment shall be provided for turbine and generators. Suitable circuits shall be provided
for abnormal conditions such as increase in bearing temperature, low oil pressure etc. A
protection scheme with automatic control circuit shall be provided to stop the turbine in the
event of power supply failure or any other fault by operating emergency solenoid of power
pack. It is proposed to provide:-
Control switch, indicating meters and position indicator lamps on the control panel.
Protective relays for machine control and alarm units etc. on the units control board.
Control and relays for the power circuit are provided on the separate gear cubical which also
houses the incoming and outgoing LT bus.
Suitable provision for all the electrical equipment in power house and switch yard etc. to
provide full protection to equipment and working persons in the event of short circuiting
and other faults.
Generator Protection and Metering
a) LAVT Panel
The lightening arrestor and the voltage transformer panel shall be located near the
generator and shall house the surge arrestor and PT with necessary fuses etc.
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Developer:- Tek Singh Rathore
b) NGC
The neutral grounding cubicle shall have leads from all the three winding and shall house
the protection CTs for differential protection, neutral forming link and earthing resistor,
CT for stator earth fault protection.
c) Protections
Following protections shall be provided for the Turbine generator set in Generator
Control panel.
- Generator differential protection.
- Voltage restrained over current relay.
- Earth fault relay.
- O/V and U/V relay.
- Phase unbalance relay.
- Over speed relay and switch.
- Stator Temperature Detector.
- Field failure/Diode Failure relays.
Following indicating and logging meters too shall be provided.
- Current for all the three phases.
- Voltmeter with selector switch.
- KW meter with Kwh logging.
- Pf meter.
- Unit running hour meter.
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Electrical Auxiliaries and Equipments:-
Power plant controls and monitoring system shall have microprocessor based controls
comprising controls for unit control, switching equipment and auxiliaries. The system
shall also have provision for data logging periodical report generation and alarm and
annunciation. The control and monitoring equipment shall also have provision for remote
control and remote alarm and annunciation.
7.8 Auxiliary Mechanical services
(i) HOT Crane
It is proposed to install a 10 tonne capacity HOT crane with auxiliary hooks of 5 tonns
designed to travel the full length of the power house. The capacity of the HOT crane has
been selected on the basis of preliminary assessment of rotor weight including the lifting
arrangement.
(ii) Ventilation & air conditioning
The powerhouse shall be provided with ventilation and air conditioning as required to
maintain the work areas, powerhouse at the selected temperature and humidity levels would
be provided for control room and offices. The temperature and humidity levels would be
selected to suit the requirement of equipment and plant staff.
(iii) Fire protection
Fire protection system complete with CO2 cylinders, ring headers, discharge nozzles shall
be provided. This system shall be complete with manual operation facility to release
carbon dioxide.
(iv) Water Cooling
A pumping system would be provided to supply adequate quantity of water from the tail race
channel for cooling of the turbine and generator bearings generator air coolers and selected
plant services.
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7.9 Electrical services
(i) A.C.auxiliary services
3 phase,11kv/415v delta/star 75KVA capacity step down transformer will used for station
lighting and heating load for power house, staff ,illumination for road and switch yard.
Emergency lights on important places will be operated by D.C.battery provided in the
power house. 50 KVA diesel generator set will also be provided for illumination in power
house, staff, street lights & switch yard during shut down of machine.
(ii) D.C. auxiliary service
Float and boost type 110 Volts,200AH battery charger and tabular battery will be
provided for feeding power to indication lamps, protection relay ,initial impulse to the
self excitation system by means of field flashing and to operate few emergency light.
(iii) Cables
H.T. cables shall be used. Heat shrink type cable termination shall be provided for H.T.
cable connecting generator to generation transformer, neutral grounding end.
(iv) SWITCH YARD
In designing Switchyard layout, the need for simple features, closeness to power house,
equipment specifications according to Indian standards, ease of operation have been kept in
view. Fencing will be provided for security reasons.
0.415KV high voltage cable laid in underground trenches will connect the feeder’s panel
with the step up transformer. Step up transformer with normal protection such as restricted
earth fault, differential etc. as per manual with circuit breakers will be provided for
disconnection of the transformers and control of the outgoing line taking off from the power
station. Lightening arrestor will be provided to protect lines and transformer from the surges.
The required rating of CT (current transformer) and PT (potential transformer) is provided
in the switchyard.
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Developer:- Tek Singh Rathore
(v)TRANSMISSION LINES
General
It is proposed to evacuate the power from switchyard of Thunag MHEP to substation at
Thunag through the 11kv single circuit line near about 2.0km long.
Power Evacuation
It is proposed that the electricity shall be generated at 0.415kV and evacuated at 11 kV switchyard.
One step up transformer, 0.415kv/11kv for each machine shall be provided switchyard near the
power house. The switch yard shall be 11kv outdoor type.