FIELD VISIT REPORT

On

KAYATHAR WIND FARM

Submitted By

N. Senthil Nathan

Kayathar is a panchayat town in Thoothukudi district in the Indian

state of Tamil Nadu. It is situated along National Highway 7 (NH7) between

Tirunelveli and Kovilpatti. It is one of the windiest regions in southern India.

Location of Kayathar in a map

Field Visit is carried out the wind farm and the Substation at Kayathar,

the trip details are given as report in two sections.

� Section I: Wind Farm Details

� Section II: Substation Details

Kayathar is a panchayat town in Thoothukudi district in the Indian

state of Tamil Nadu. It is situated along National Highway 7 (NH7) between

. It is one of the windiest regions in southern India.

Location of Kayathar in a map

Field Visit is carried out the wind farm and the Substation at Kayathar,

the trip details are given as report in two sections.

: Wind Farm Details

ubstation Details

Kayathar is a panchayat town in Thoothukudi district in the Indian

state of Tamil Nadu. It is situated along National Highway 7 (NH7) between

. It is one of the windiest regions in southern India.

Field Visit is carried out the wind farm and the Substation at Kayathar,

SECTION - I

WIND FARM DETAILS

1. INTRODUCTION

Kayathar is one of the best locations for wind turbines. Here large

numbers of wind turbines are in operation. Heavy winds in these regions are due

to Sengottai pass. Kayathar is situated in this pass. Here there is numerous wind

turbines generate electricity and feed in to the grid via Ayyanaruthu electrical

Substation. In Kayathar wind turbines are in various power producing capacities

starting from,

� 250kW

� 600kW

� 1mW

� 2 mW

A view wind turbines in Kayathar wind farm

250kW Wind Turbine 600kW Wind Turbine

2mW Wind Turbine 2mW Wind Turbine Installation

2. BASICS OPERATION OF WIND TURBINES

A wind turbine is a rotating machine which captures the power from

the wind by means of aerodynamically design blades and converts in to rotating

mechanical power. Mechanical power is taken up at the shaft in the form of a

moment at a certain rotation and is transferred to a machine (such as a generator

or a pump). The entire wind power station thus consists of a wind energy

converter (rotor), a mechanical gear and a generator.

Operations of a wind turbine in a wind farm

3. COMPONENTS OF WIND TURBINES

A grid-connected wind power station consists of a mechanical system

to capture wind and an drive train system to convert the mechanical energy in to

electrical energy and a structure to hold up in the wind. These systems are broadly

classified in detail as follows;

• Rotor

• Rotor Blades

• Hub

• Nacelle

• Gearbox

• Generator

• Brake

• Yaw Drive

• Tower

• Electronic Controller

Exploded view of wind turbine components

3.2 Rotor:

The system component of a modern wind energy converter that transforms

the energy contained in the wind into mechanical rotations is referred to as rotor.

It consists of one or several rotor blades and the rotor hub. The rotor blades

extract part of the kinetic energy from the moving air masses according to the lift

principle.

3.1 Rotor Blades:

Blades of the wind turbine have airfoil sections. It captures the energy from

the wind and transfers it power to the hub. Almost all commercial designs have

three bladed rotors. The wind turbine blade is shown in figure below,

A view of 40m blades ready for transportation

3.3 Hub:

The rotor hub connects the rotor blades to the rotor shaft .The hub is the

supporting structure between the blades and the main shaft in the nacelle.

A typical hub

It is also the place where the power of the turbine is controlled physically

pitching the blades.

3.4 Nacelle:

The nacelle cover is the wind turbine housing protects turbine components

from atmospheric weather conditions and it reduces emitted mechanical sound. It

is made up of FRP material.

A typical nacelle is being transported

3.5 Gear Box:

Gear box is an important component in the power trains of a wind turbine.

Speed of a typical wind turbine rotor may be 30 to 50 r/min whereas, the optimum

speeds of generator may be around 1000 to1500 r/min. Hence, gear trains are to

be introduced in the transmission line to manipulate the speed according to the

requirement of the generator. An ideal gear system should be designed to work

smoothly. There are lots of gear wheels in the gearbox. The wheels attached in to

each gear.

Exploded View of a typical planetary gear box

3.6 Generator:

All grids connected wind turbine drive three phase alternating current

generators to convert mechanical energy in to electrical energy. The fixed speed

generator is as shown in fig 7.

A fixed pole Generator

Types of generators:

• Synchronous generator

• Asynchronous Generator

A synchronous generator or alternator operates at exactly the same

frequency as the network to which it is connects. An asynchronous generator or

induction generator operates at slightly higher frequency than the network. Both

the generators have a non rotating part called the stator and rotating part called

rotor.

Both types of stator are connected to the network and have three phases

winding on a laminated core. They produce magnetic field rotating at constant

speed. Synchronous generator has a field winding through which passes a DC

current: this is the field winding. The field winding creates a constant magnetic

field, which locks in to the rotating filed created by the stator winding. Thus the

rotor always rotates at a constant speed in synchronism with the stator field and

network frequency.

The rotor of an induction generator is quite different .It consists of squirrel

cage of bars, short-circuited at each end. There is no electrical connection to the

rotor, and the rotor currents are induced by the relative motion of the rotor against

the rotating field of the stator. If the rotor speed is exactly equal to the speed of

the rotating field produced by the stator there is no relative motion, no induced

current. Therefore induction generator always operates at a speed is slightly

higher than speed of rotating filed.

3.7 Brake

During the periods of extremely high winds, wind turbines should be

completely stopped for its safety. Similarly, if the power line fails or the generator

is disconnected due to some reason or the other, the wind turbine would rapidly

accelerate. This leads the turbine to run-away condition within a few seconds.

Nearly all wind turbines employ a mechanical brake somewhere on the drive train.

Such a brake is normally included in addition to any aerodynamic brakes. In case

some current design standards require two independent brakes system, one of

which is usually aerodynamic and other of which is on the drive train. In most

case mechanical brake is capable of stopping the machine. In other cases, the

mechanical brake is only used for braking wind turbines

Mechanical Disc brake in operation

3.8 Yaw Drive:

A horizontal axis wind turbine has a yaw system that turns the nacelle

according to the actual wind direction, using a rotary actuator engaging on a gear

ring at the top of the tower. Yaw drive used for rotate the nacelle with respect to

the tower on its slow bearing .Yaw system keeps the turbine facing in the wind

Yaw drive system

3.9 Tower:

Tower is one of the main components of the horizontal axis wind

turbine. It raises turbine up in the air. The main function of the tower of a

horizontal axis converter is to enable wind energy utilization at sufficient heights

above ground, to absorb and securely discharge static and dynamic stress exerted

on the rotor, the power train and the nacelle into the ground. Another key factor

regarding tower dimensions and design is the natural vibration of the tower-

nacelle-rotor overall system in view of the prevention of dangerous resonance,

particularly during rotor startup. Further influencing factors are dimensions and

weight regarding transport requirements and thus available roads, erection

methods, cranes and accessibility of the nacelle as well as long-term properties

such as weathering resistance and material fatigue. Most towers are made of steel

and/or concrete. As far as steel constructions are concerned, besides the lattice

towers usually observed for dated converters, there are also anchored and self-

supporting tubular steel towers in closed, commonly conic design; the latter being

the most common tower type applied nowadays.

Different types of towers

3.10 Electronic Controller:

In one way or another controller is involved in almost all decision-making

processes in the safety systems in a wind turbine. At the same time it supervises

the normal operation of the wind turbine and carries out measurements for

statistical use. The controller is based on the use of a micro computer, specially

designed for industrial use The control program itself is not stored in a hard disk,

but is stored in a microchip. The processor that does the actual calculations is

likewise a microchip. The computer is placed in the control cabinet together with

a lot of other types of electro-technical equipment, contactors, switches, fuses,

etc.,. The many and varied demands of the controller result in a complicated

construction with a large number of different components.

The controller measures the following parameters as analogue

� Voltage on all three phases

� Current on all three phases

� Frequency on one phase

� Temperature inside the nacelle

� Generator temperature

� Gear oil temperature

� Gear bearing temperature

� Wind speed

� The direction of yawing

� Low-speed shaft rotational speed

� High-speed shaft rotational speed

The controller also measures the following parameters as digital Wind direction

� Over-heating of the generator

� Hydraulic pressure level

� Correct valve function

� Vibration level

� Twisting of the power cable

� Emergency brake circuit

� Overheating of small electric motors for the yawing, hydraulic pumps, etc

� Brake-caliper adjustment

SECTION - II

SUB STATION DETAILS

1. INTRODUCTION

The wind power generated from the wind farm are fed in to this substation

and then exported to national grid for respective loads. All the voltages generated

from the wind turbines are in the order of 490/600/690VC respectively are

stepped up in to 11kV /33kV by the step up transformer and conned by the feeders

and terminate at the substation transformer.

At the substation the incoming feeders are stepped up to higher voltages in

the range of 110kV/ 230kV and fed to the National grid and distributed to the

various loads.

Power transmission from a wind farm to the grids

2. TRANSMISSION LINE DETAILS:

TNEB is ACSR 7/3.35 type Transmission lines are used for reducing

cost as well as good transmission efficiency with good mechanical strength.

3. SUB-STATION DETAILS:

The generated electricity from the various wind turbines are connected the power

transformer via 14 feeders in Ayyanaruthu substation.

View of Ayyanaruthu Sub Station with the power transformer

4. MAJOR COMPONENTS OF SUB STATION

The equipment required for a transformer Sub-Station depends upon

the type of Sub-Station, Service requirement and the degree of protection desired.

Ayyanaruthu Sub-Station has the following major equipments:-

4.1 Bus-Bar:

When a no. of lines operating at the same voltage have to be directly

connected electrically, bus-bar are used, it is made up of copper or aluminum bars

(generally of rectangular X-Section) and operate at constant voltage.

4.2 Insulators:

The insulator serves two purposes. They support the conductor (or

bus bar) and confine the current to the conductor. The most commonly used

material for the manufactures of insulators is porcelain. There are several type of

insulator (i.e. pine type, suspension type etc.) and their use in Sub-Station will

depend upon the service requirement.

4.3 Isolating Switches:

In Sub-Station, it is often desired to disconnect a part of the system

for general maintenance and repairs. This is accomplished by an isolating switch

or isolator. An isolator is essentially a knife Switch and is design to often open a

circuit under no load, in other words, isolator Switches operates only when the

line is connected and carry no load.

.

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4.4 Circuit Breaker:

A circuit breaker is a equipment, which can open or close a circuit

under normal as well as fault condition. These circuit breaker breaks for a fault

which can damage other instrument in the station. It is so designed that it can be

operated manually (or by remote control) under normal conditions and

automatically under fault condition. A circuit breaker consists of fixed & moving

contacts, which are touching each other under normal condition i.e. when breaker

is closed. Whenever a fault occurs trip coil gets energized, the moving contacts are

pulled by some mechanism & therefore the circuit is opened or circuit breaks. When

circuit breaks an arc is stack between contacts, the production of arc not only

interrupts the current but generates enormous amount of heat which may cause

damage to the system or the breaker itself. Therefore the main problem in a circuit

breaker is to extinguish the arc within the shortest possible time so that the heat

generated by it may not reach a dangerous value. The medium used for arc

extinction is usually Oil, Air, Sulfur Hexafluoride (SF6) or vacuum.

4.5 Protective relay:

A protective relay is a device that detects the fault and initiates the

operation of the C.B is to isolate the defective element from the rest of the system”.

The relay detects the abnormal condition in the electrical circuit by constantly

measuring the electrical quantities, which are different under normal and fault

condition. The electrical quantities which may change under fault condition are

voltage, current, frequency and phase angle. Having detected the fault, the relay

operates to close the trip circuit of C.B.

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4.6 Instrument Transformers:

The line in Sub-Station operates at high voltage and carries current of

thousands of amperes. The measuring instrument and protective devices are

designed for low voltage (generally 110V) and current (about 5A).Therefore,

they will not work satisfactory if mounted directly on the power lines. This

difficulty is overcome by installing Instrument transformer, on the power lines.

There are two types of instrument transformer.

(i) Current Transformer:

A current transformer is essentially a step-down transformer. It steps-

down the current in a known ratio, the primary of this transformer consist of one or

more turn of thick wire connected in series with the line. The secondary consist of

thick wire connected in series with line having large number of turn of fine wire and

provides for measuring instrument, and relay a current, which is a constant faction

of the current in the line. Current transformers are basically used to take the

readings of the currents entering the substation.

(ii)Voltage Transformer or Potential Transformer:

It is essentially a step–down transformer and step down the voltage in

known ratio. The primary of these transformers consists of a large number of

turn offline wire connected across the line. The secondary windings consists of

a few turns, provides for measuring instruments, and relay a voltage that is known

fraction of the line voltage.

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CONCLUSION

This filed visit gave me an opportunity to see and experience the real

time wind turbines in operation and came to know how the wind turbine works/

operates. Also the field visit gave me the picture of how power generated from

wind turbines is fed in to grid / connected to load.

The visit helped me to understand the operation of various

equipments in the substation. The protection arrangements and safety measures

are also known. The important electrical parameters to be noted and the essence

of safe operation of equipments and precaution while fault and rectification of the

fault were also clearly understood.