INDUSTRIAL TRAINING REPORT

110KV SUBSTATION KAZHAKOOTTAM

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AcknowledgementWe the students of Govt. Rajiv Gandhi Institute Of Technology, Kottayam, have undertaken practical training at 110 KV Substation Kazhakoottam, under the guidance and supervision of Mr Pardha Radha K.S (Assistant Engineer) of 110KV Substation Kazhakoottam. We are thankful to all the employees of this substation who helped us to gain the practical knowledge and answered our queries to the best of our satisfaction. We feel obliged by gaining knowledge under the esteemed guidance of able personals at Kazhakoottam substation.

During the training from 7-7-2014 to 11-7-2014 we have prepare d this report of practical training, which gives insight information about instruments and apparatus used in this system and their working in brief. We can say that this report is a summary of what we have observed and learned there.

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CONTENTS1. Introduction

2. Substation.

3. Elements of Substation

3.1. Power Transformer

3.2. Circuit Breaker

3.2.1. SF6 Circuit Breaker

3.2.2. Vacuum Circuit Breaker

3.3. Instrumental Transformers

3.3.1. Potential Transformer

3.3.2. Current Transformer

3.4. Isolator

3.5. Insulator

3.6. Wave Trap

3.7. Bus Bars

3.8. Relays

3.9. Lightning Arresters

3.10. DC Supply

3.11. Battery Charger

3.12. Switch Yard

3.13. Steel Towers

4. 110 KV Substation Kazhakoottam

5. Single Line Diagram

6. Details of 110 KV Substation Kazhakoottam

7. Conclusion

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1.INTRODUCTIONWe all know that electrical power systems are playing an important role in our daily routine. Electrical power is generated in power stations by different processes and from there it is transmitted to substations, which are located in different places through transmission lines. Then it is delivered to the consumer through a large network of transmission and distribution cables.

In electrical systems the most important components are the Power Transformers, circuit breakers, lightning arresters, instrument transformers, relays, wave traps, isolators, bus bars etc.

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2.SUB –STATION Substation is a part of an electrical generation transmission and distribution system. Substation transforms voltage from high to low, or the reverse or performs any of the several other important functions. Between generating station and consumer electric power may flow through several substations at different voltage levels.

Substations may be owned and controlled by an electrical utility, or may be owned by a large industrial or commercial customer. Generally substations are unattended, relying on SCADA for remote supervision and control.

Substations may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages. The word substation comes from the days before the distribution system became a grid. As central generating stations became larger, smaller generating plants were converted to distribution stations, receiving their energy supply from a larger plant instead of using their own generators. The first substations were connected to only one power station, where the generators were housed, and were subsidiaries of that power station.

The electrical substation design is influenced by following aspects:

1. Rated voltage of incoming and outgoing lines

2. Total MVA to be transferred

3. Geographical area available

4. Step up and step down

5. Switching substation

6. Receiving substation

7. Distributing substation

8. Industrial substation

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3.ELEMENTS OF SUBSTATION

3.1.Power Transformer

The Power Transformers are those transformers installed at the ending or receiving end of long high voltage transmission lines. The distribution transformers (generally pole mounted) are those installed in the location of the city to provide utilization voltage at the consumer terminals. Power transformers are used in transmission network of higher voltages for step-up and step down application (400 kV, 200 kV, 110 kV, 66 kV, 33kV) and are generally rated above 200MVA.They have usually has one primary and one secondary, and one input and output.

Power transformers generally operate at nearly full – load. However, a distribution transformer operates at light loads during major parts of the day.The performance of the power transformers is generally judged from commercial efficiency. The rating of a high transformer is many times greater than that of distribution transformer and the flux density is also higher

Power transformer’s primary winding always connected in star and secondary winding in delta In the Substation end of the transmission line, The power transformer connection is star-delta.( for the purpose of step down the voltage level)

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In the star up of the transmission line (H-T), the connection of the power transformer is delta – star (for the purpose of step up the voltage level)

Transformer Core

A physical core is not an absolute requisite and a functioning transformer can be produced by placing the windings near each other, an arrangement termed as ‘air-core’ transformer. The air which comprises the magnetic circuit is essentially lossless, and so and air core transformer eliminate loss due to hysteresis in the core material. The leakage inductance is inevitably high resulting in very poor regulation, and so such designs are unsuitable for use in power distribution. They have however very high bandwidth, and are frequently used in radio-frequency applications for which a satisfactory coupling coefficient is maintained by carefully overlapping the primary and secondary windings. They are also used for resonant transformers such as tesla coils where they can achieve reasonably low loss in spite of the high leakage inductance.

Windings

The conducting materials used for the winding depends upon the application, but in all cases the individual turns must be electrically insulated from each other to ensure that the current travels throughout every turn. For small power and signal transformers, in which currents are low and the potential difference between adjacent turns is small, the coils are often wound from enamelled magnet wire, such are Formvar wire. Larger power transformers operating at high voltages may be wound with copper rectangular strip conductors insulated by oil-impregnated paper and blocks of pressboard.

Bushings

Large transformers are provided with high voltage insulate bushings made of polymers or porcelain. A large bushing can be a complex structure since it must provide careful control if the electric field gradient without letting transformer leak.

Tap Changer

A tap changer is a connection point selection mechanism along a power transformer winding that allows a variable number of turns to be selected in discrete steps. A transformer with a variable turns ratio is produced, enabling

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stepped voltage regulation of output. The tap selection may be made via an automatic or manual tap changer mechanism.

Cooling Equipment

ONAN Cooling of Transformer

This is the simplest form of cooling system. The full form of ONAN is “Oil Natural Air Natural”. Here natural convectional flow of hot oil is utilized for cooling. In convectional circulation of oil, the hot oil flows to the upper portion of the transformer tank and the vacant place is occupied by cold oil. This hot oil which comes to the upper side will dissipate heat in the atmosphere by natural conduction, convection and radiation in air and will become cold. In this way the oil in the transformer continually circulate when the transformer is put into load. As the rate of dissipation of heat in air depends on dissipating surface of the oil tank, it is essential to increase the effective surface area of the tank, so additional dissipating surface in the form of tubes or radiators are connected to the transformer tank. This is known as radiator bank of transformer.

ONAF Cooling of Transformer

Heat dissipation can obviously be increased by increased by increase in surface area, but it can be made further faster by applying forced air on that dissipating surface. Fans blowing air on cooling surfaces is employed. Forced air takes away the heat from the surface of the radiator and provides better cooling than natural air. The full form of ONAF is “Oil Natural Air Forced”. As the heat dissipation rate is faster and more in ONAF transformer cooling method than in ONAN cooling system, electrical power can be put into more load without crossing the permissible temperature limits.

OFAF Cooling of Transformer

The heat dissipation rate can be still improved if the oil circulation is accelerated by applying some force. In OFAF cooling system the oil is forced to circulate within the closed loop of the transformer tank by means of oil pumps. OFAF means “Oil Forced Air Force” cooling methods of transformer. The main advantage of this system is that it is a compact system and for same cooling capacity OFAF system occupies much lesser space than former two systems of transformer cooling. Actually in Oil Natural cooling systems , the heat comes out of the conducting part of the transformer is displaced form its position, is a

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slower rate due to convectional flow of oil but in oil forced cooling systems the heat is displaced from its origin as soon as it comes out in the oil, hence rate of cooling becomes faster.

For all T-6 models – 0.35to .84kg/cm2(any one value as per demand) For all T-3 models – 0.35to .84kg/cm2(any one value as per demand)

Port openings

For all T-6 models- about 150mm Dia. For all T-3 models- about 70mm Dia.

Oil/Winding Temperature indicator

Scientific Controls Mechanical Instruments are incorporates proven design features acquired from many years of experience in providing Temperature Indicators/Controllers for Power & Distribution Transformers.

Oil Temperature Indicator: The Oil Temperature Indicator (OTI) measures the Top oil Temperature. It is used for control and protection for all transformers.

Winding Temperature Indicator

The winding is the one component with highest temperature within the transformer and, above all, the one subject to the fastest temperature increase as the load increases. Thus to have a total control of temperature parameter within the transformer, the temperature of winding as well as top oil must be measured. An indirect system is used to measure winding temperature as it is dangerous to place a sensor close to the winding due to heavy voltage. The indirect measurement is done by means of a built-in Thermal Image.

Winding Temperature Indicator is equipped with a specifically designed Heater which is placed around the operating bellows through which passes a current proportional to the current passing through the transformer winding subject to the given load. Winding temperature is measured by connecting the CT Secondary of the transformer through a shunt resistor inside the Winding Temperature Indicator to the Hater Coil around the operating Bellows. It is possible to adjust gradient by means of Shunt Resistor.

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In this way the value of the winding temperature indicated by the instrument will be equal to the one planned by the transformer manufacturer for a given transformer load.

3.2.Circuit Breaker

A circuit breaker is a manually or automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and interrupt current flow. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.

Operation

All circuit breakers have common features in their operation, although details vary substantially depending on the voltage class current rating and type of the circuit breaker.

The circuit breaker must detect a fault condition; in low voltage circuit breakers this is usually done within the breaker enclosure. Circuit breakers for large currents and high voltages are usually arranged with pilot devices to sense a fault current and to operate the trip opening mechanism. The trip solenoid that releases the latch is usually energized by a separate battery, although some high

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voltage circuit breakers are self-contained with current transformers, protective devices and internal control power source.

Once a fault is detected, contacts within the circuit breaker must open interrupt the circuit; some mechanically stored energy (using something such as springs or compressed air) contained within the breaker is used to separate the contacts, although some of the energy required may be obtained from the fault current itself. Small circuit breakers maybe manually operated, larger units have solenoids to trip the mechanism, and electric motors to store the energy to the springs.

The circuit breaker contacts must carry the load current without heating, and must also with stand the heat of the arc produced when interrupting (opening) the circuit. Contacts are made of copper or copper alloys, silver alloys and other highly conductive materials. Service life of the contacts is limited by the erosion of contact material due to arcing while interrupting the current. Miniature circuit breakers (MCB) and moulded-case circuit breakers (MCCB) are usually discarded when the contacts have worn, but power circuit breakers and high voltage circuit breakers have replaceable contacts.

When a current is interrupted, an arc is generated. This arc must be contained, cooled and extinguished in a controlled way, so that the gap between the contacts can again withstand the voltage in the circuit. Different circuit breakers use vacuum, air, insulating gas, or oil as the medium the arc forms in. Different techniques are used to extinguish the arc including.

Lengthening / deflection of the arc Intensive cooling ( in jet chamber) Division into partial arcs Zero point quenching (Contacts open at the zero current time crossing of

the AC waveform, effectively breaking no load current at the time of opening. The zero crossing occurs at twice the line frequency, i.e. 100 times per second for 50 Hz and 120 times per second for 60 Hz)

Connecting capacitors in parallel with contacts in DC circuits

Finally, once the fault condition has been cleared, the contact must again be closed to restore power to the interrupted circuit.

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3.2.1.Sf6 Circuit Breaker

A circuit breaker in which the current carrying contacts operate in Sulphur Hexafluoride or SF6 gas is known as an SF6 Circuit Breaker.

SF6 has an excellent insulating property. SF6 has high electronegativity. That means it has high affinity of absorbing free electron. Whenever a free electron collides with SF6 gas molecule, it is absorbed by that gas molecule and forms a negative ion.

The attachment of electron with SF6 gas molecule may occur in two different ways

1)SF6 + e = SF6-

2)SF6 + e = SF5-+F

These negative ions obviously much heavier than a free electron and therefore over all mobility of the charged particle in the SF6 gas is much less as compared to other common gases. We know that mobility of charged particle is responsible for conducting current through a gas.

Hence for heavier and less mobile charged particle in SF6 gas, it acquires gas very high dielectric strength. Not only the gas has a good dielectric strength but also it has the unique property of fast recombination after the source energizing the spark is removed. The gas has also very good heat transfer property. Due to its low gaseous viscosity (because of less molecular mobility) SF6 gas can efficiently transfer heat by convection. So due to its high dielectric strength and high cooling effect SF6 gas is approximately 100 times more effective arc quenching media than air. Due to these unique properties of this gas SF6 Circuit

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Breaker is used in complete range of medium voltage and high voltage electrical power system. These circuit breakers are available for the voltage ranges from 33KV to 800KV and even more.

3.2.2.Vacuum Circuit Breaker

A vacuum circuit breaker is such kind of circuit breaker where the arc quenching takes place in vacuum. The technology is suitable for mainly medium voltage application. For higher voltage vacuum technology has been developed but not commercially viable. The operation of opening and closing of current carrying contacts and associated arc interruption takes place in a vacuum chamber in the breaker which is called vacuum interrupter. The vacuum interrupter consists of a steel arc chamber in the centre symmetrically arranged ceramic insulators. The vacuum pressure inside a vacuum interrupter is normally maintained at 10-6 bar.

3.3.Instrumental Transformers Instrument Transformers are high accuracy class electrical devices used to isolate or transform voltage or current levels. The most common usage of instrument transformer is to operate instruments or metering from high voltage or high current circuits, safely isolating the secondary control circuitry from the high voltages or currents. The primary winding of the transformer is connected to the high voltage or high current circuit, and the meter or relay is connected to the secondary circuit.

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Instrument transformers may also be used as an isolation transformer so that secondary quantities may be used in phase shifting without affecting other primary connected devices.

In Kazhakoottam Substation there are a total of current transformers and potential transformers. They are mainly used for metering purpose and protection by operation of various relays.

TYPES:

3.3.1. Potential Transformer

Potential transformers are also called voltage transformers (VT) are a parallel connected type of instrument transformer. They are designed to present negligible load to the supply being measured and have an accurate voltage ratio and phase relationship to enable accurate secondary connected metering.

3.3.2. Current Transformer

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Current transformers (CT) are a series connected type of instrument transformed. They are designed to present negligible load to the supply being measured and have an accurate current ratio and phase relationship to enable accurate secondary connected metering.

Current transformers are often constructed by passing a single primary turn either an insulated cable or an uninsulated bus bar through a well-insulated toroidal core wrapped with many turns of wire. This affords easy implementation on high voltage bushing insulators and using the pass-through conductor as a single turn primary.

A current clamp uses a current transformer with a split core that can be easily wrapped around a conductor in circuit. This is a common method used in portable current measuring instruments but permanent installations use more economical types of current transformer. Specially constructed wireband CTs are also used, usually with an oscilloscope, to measure high frequency waveforms or pulsed currents within pulsed power systems. One type provides an IR voltage output that is proportional to the measured current; another called a Rogowski coil, requires an external integrator in order to provide a proportional output.

3.4.Isolator

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Circuit breakers always trip the circuit but open contacts of breaker cannot be physically visible from outside of the breaker and that is why it is recommended not to touch any electrical circuit by just switching off the circuit breaker. So for better safety there must be some arrangement so that one can see open condition of the section of the circuit before touching it. Isolator is a mechanical switch which isolates a part of circuit from system as when required. Electrical isolators separate a part of the system from rest for safe maintenance works. So definitions of isolator can be rewritten as Isolator is a manually operated mechanical switch which separates a part of the electrical power normally at off load condition.

Isolators are classified into two:

1. Line Isolator

2. Bus Isolator

Line Isolator

Line Isolator is the isolator which is situated in between potential transformer and current transformer. This is the isolator which is coming directly from line. This isolator has an inbuilt provision for grounding the main transmission lines so that work can be done on them.

Bus Isolator

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This is the isolator which is coming directly from the bus. They are used to isolate the various buses present in the switch yard.

3.5.Insulators

An insulator is a material whose internal electric charges do not flow freely, and therefore very hard to conduct an electric current under the influence of an electric field. A perfect insulator does not exist, but some materials such as glass, paper and Teflon which have high resistivity, are very good electrical insulators. A much larger class of materials, even though they may have lower bulk resistivity, are still good enough to insulate wiring and cables. Examples include rubber like polymers and most plastics. Such materials can serve as practical and safe insulators for low to moderate voltages.

Insulators are used in electrical equipment to support and separate electrical conductors without allowing current through themselves. An insulating material used in bulk to wrap electrical cables or other equipment is called insulation. The term insulator is also used more specifically to refer to insulating supports used to attach electric power distribution or transmission lines to utility poles and transmission towers hold the conductors and prevent current through conductors to pass through the poles to the ground.

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3.6.Wave Trap

Wave traps in electrical systems are used for power plant communication through transmission wires. It is a combination of low inductances in series and high capacitances in parallel with transmission wires in power frequencies. But communication signals are very low amplitude and very high frequency signals. So, these signals are nearly open circuited by the inductance and short circuited by capacitance. That is how wave trap power and communication waves are used in PPC

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3.7.Bus Bars

In electrical power distribution, a bus bar is also spelled as busbar or sometimes incorrectly as buss bar, with the term bus being a contraction of the Latin word omnibus. It is a strip or bar of copper, brass or aluminium that conducts electricity within a switchboard, distribution, substation, battery bank or other electrical apparatus. Its main purpose is to conduct electricity, not to function as a structural member.

The cross-section size of the bus bar determines the maximum amount of current that can be safely carried. Bus bars can have cross sectional area as little as 10 mm2 but electrical substations may use metal tubes of 50 mm in diameter (20 mm2

) or more as bus bars. An aluminium smelter will have very large bus bars used to carry tens of thousands of amperes to the electrochemical cells that produce aluminium from molten salts.

3.8.Relays A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used, where it is necessary to control a circuit by a low-power signal

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(with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the signal coming from one circuit and re-transmitting it to another. Relays were extensively used in telephone exchanges and early computer to perform logical operations.

A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload faults; in modern electrical power systems these functions are performed by digital instruments called “protective relays”.

Electromagnetic Relay

Electromagnetic relays are those relays which are operated by electromagnetic action. Modern electrical protection relays are mainly microprocessor based, but still electromagnetic relay holds its place. It will take much longer time to be replaced the all electromagnetic relays by microprocessor based static relays. So before going through details of protection relay system we should review various types of electromagnetic relays.

Electromagnetic Relay Working

Practically all the relaying device are based on rather one or more of the following types of electromagnetic relays.

a) Magnitude measurement

b) Comparison

c) Ratio measurement

Principle of electromagnetic relay working is on some basic principles. Depending upon working principle these can be divided into following types of electromagnetic relays.

i) Attracted Armature type relayii) Induction Disc type relay

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iii) Induction Cup type relayiv) Balanced Beam type relayv) Moving Coil type relayvi) Polarised Moving Iron type relay

Attraction Armature Type Relay

Attraction Armature type relay is the most simple in construction as well as its working principle. These types of electromagnetic relays can be utilized as either magnitude relay or ratio relay. These relays are employed as auxiliary relay, control relay, overcurrent, undercurrent, overvoltage, undervoltage and impedance measuring relays.

Hinged armature and plunger type constructions are most commonly used for these types of electromagnetic relays. Among these two constructional designs, hinged armature type is more commonly used.

3.9.Lightning Arresters

A lightning arrester, also known as lightning conductor, is a device used to on electrical power systems and telecommunication systems to protect the insulation and conductors of the system from the damaging effects of lightning. The typical lightning arrester has a high voltage terminal and a ground terminal. When a lightning surge (or switching surge, which is very similar)

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travels along the power line to the arrester, the current from the surge is diverted through the arrester, in most cases to the earth

In telegraphy and telephony, a lighting arrester is placed where wires enter a structure, preventing damage to electronic instruments within and ensuring the safety of individuals near them. Smaller versions of lighting arresters also called surge protectors are devices that are connected between each electrical conductor in power and communication systems and the earth. These prevent the flow of the normal power or signal currents to ground, but provide a path over which high voltage lightning current flows, bypassing the connected equipment. Their purpose is to limit the rise in voltage when a communication or power line is struck by lightning or is near to a lightning strike.

If the protection fails or is absent, lightning that strikes the electrical system introduces thousands of kilovolts that may damage the transmission lines, and can also cause severe damage to transformers and other electrical or electronic devices. Lightning produce extreme voltage spikes in incoming power lines can damage electrical home appliances.

3.10. DC Supply

DC Supply is one of the most essential parts of a substation because all the relays are working on DC Supply. So even if AC Supply is not available the circuit breaker should work. For this DC Supply is very essential.

3.11.Battery Charger

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The battery charger is used to provide dc supply to the substation. It is used to convert the AC signal to DC signal, for that purpose it employs a rectifier circuit.

3.12.Switch Yard

Switch yard is the most important part of a substation. In switch yard most of the part is laid with metals to reduce earthed voltage. In the switch yard the supply taken from incoming feeders are transferred to one or more bus bars from which they are switched on or off to various incomers and distribution auxiliary supply etc.

3.13.Steel Towers (Transmission Towers)

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A transmission tower (colloquially termed an electricity pylon in the United Kingdom and part of Europe, and a hydro tower in certain provinces of Canada where power generation is mainly hydroelectric) is a tall structure, usually a steel lattice tower, used to support an overhead power line. They are used in high voltage AC and DC systems, and come in a wide variety of shapes and sizes. Typical height ranges from 15 to 55 metres (49 to 180 ft) though the tallest are the 370 metre (1214 ft) towers of a 2700 metre long span of Zhoushan Island Overhead Power line Tie. In addition to steel, other materials may be used including concrete and wood.

There are four major categories of transmission towers: Suspension, Terminal, Tension, and Transposition. Some transmission towers combine these basic functions. Transmission towers and their overhead power lines are often considered to be a form of visual pollution. Methods to reduce the visual effect include undergrounding.

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4. 110 KV SUBSTATION KAZHAKOOTTAMThe Kazhakoottam Substation is located near the Techno Park in Kazhakoottam Trivandrum. It is a 110 KV Substation established on mainly for providing power to Trivandrum Techno Park and was named Techno Park Substation at that time. It was later renamed as Kazhakoottam Substation on .

CAPACITY OF SUBSTATION

Capacity of a substation depends on number of its transformers present. In Kazhakoottam substation there are 4 transformers in which 2 transformers are 10 MVA and other two are 12.5 MVA so total capacity of Kazhakoottam substation is 45 MVA.

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5.SINGLE LINE DIAGRAM

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5.Details of 110 KV Substation KazhakoottamPower Transformers

The substation started with two 10 MVA power transformers for providing the power requirements of Techno Park. ONAN cooling system is used in these transformers. Later two more 12.5 MVA transformers were added by providing connection through an auxiliary bus to manage additional power requirements of nearby local areas. These 12.5 MVA transformers can also be used as 10 MVA transformers by using ONAN cooling (without using forced air) or as 12.5 MVA transformers (by switching on fans for providing forced air.

TRANSFORMER RATED CURRENT

HV LV

1: 10 MVA TRANSFORMER NO:1 52.5A 525A

2: 10 MVA TRANSFORMER NO:2 52.5A 525A

3: 12.5 MVA TRANSFORMER NO:3 65.525A 656.25A

4: 12.5 MVA TRANSFORMER NO:4 65.525A 656.25A

11KV Incomers

There are four 11KV incomers coming out of the four power transformers.

INCOMER CT RATIO

1: 11KV INCOMER NO:1 1000/5

2: 11KV INCOMER NO:2 1000/5

3: 11KV INCOMER NO:3 800/5

4: 11KV INCOMER NO:4 800/5

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Feeders

Feeders are conductors which carry electric power from the service equipment (or generator switchboard) to the overcurrent devices for groups of branch circuits or load centres supplying various loads.

The outgoing 11KV feeders present in Kazhakoottam Substation are given below.

11KV Feeders

NAME OF FEEDERS CT RATIO

1:SREEKARYAM FEEDER 200/5

2:UNIVERSITY FEEDER 200/5

3:TOWN FEEDER 200/5

4:KULATHOOR FEEDER 400/5

5:AUXILIRY FEEDER 200/5

6:KARYAVATTOM FEEDER 200/5

7:VIZHINJAM FEEDER 400/5

8:TECHNO PARK NO:1 400/5

9:TECHNO PARK NO:2 400/5

10:TECHNO PARK NO:3 400/5

11:TECHNO PARK NO:4 400/5

Circuit breakers

In Kazhakoottam Substation SF6 circuit breakers and Vacuum circuit breakers are used for cutting off current flow. The SF6 circuit breakers are larger in size and are used in breaking current in the 110KV side and are located in the main switch yard. The Vacuum circuit breakers are smaller and compact and are located inside the main building in the 11KV side.

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Battery Charger

The battery charger present in Kazhakoottam Substation charges the 110 V DC battery source by taking 3 phase power from its auxiliary 3 phase AC supply and charges the batteries when this supply is available. The specifications of battery charger present in Kazhakoottam substation are given below.

Input

MAKE : WAVE ELECTRONICS

I/P FREQUENCY : 50HZ

NO OF PHASE : 3

RATED VOLTAGE : 415 V

O/P RATED CURRENT : 30 A

RATED DC VOLTAGE : 120V

Output

Rated DC Voltage : 110V

Rated Current : 30A

Station Battery

The battery supply present in Kazhakoottam substation provide DC supply to the substation when auxiliary AC supply is cut off so that rectified DC supply is unavailable. In Kazhakoottam substation 55 batteries of 2 volt are provided giving a total of 110 volt. The specifications of station battery present in Kazhakoottam substation is given below.

MAKE : AMARAJA INDIAN POWER STACK

NO OF CELLS : 55

CAPACITY : 200 Ah

VOLTAGE OF ONE CELL : 2.188 V

TOTAL VOLTAGE : 110 V

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6.CONCLUSION It has really been a knowledge experience pursuing training at 110KV Kazhakoottam substation. The phase of practical training has proved to be quiet fruitful, beneficial in every respect. It provided an opportunity to encounter big and sophisticated equipment of the substation. The architecture of the substation and the way various equipment are linked together to work as a unit and methodological approach in working of whole substation is controlled renders the impression that engineering is not just learning the structured description and working of various equipment, but greater part is of planning proper management. It was definitely a knowledge experiences and no doubt it showed that mere theoretical and bookish knowledge need to be supplemented with able practice knowledge and this opportunity to gain practical knowledge, imparted by vary able personals of Kazhakoottam substation, was a learning experience.

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