Training Report:132/33 kv (Hybrid) GSSSms Substation,Jaipur

Summer training Session 2015

Aishwarya sharmaDurgesh ManeshwarMithlesh kumar Tak

Priya SharmaShantanu Singh

Malaviya National Institute of Tech-nology, Jaipur -———————————————————————————-

AcknowledgementsI feel immense pleasure in conveying my heartiest thanks and deep sense of gratitude to Mr. VikasGupta, HoD Electrical Engineering Department at Malaviya National Institute of Technology,

Jaipur for his efforts and for technical as well as moral supprt. I feel indebted to express myheartiest thanks and gratitude to Mr. Anurag Vats(AEN), Mrs. kusum lata,Mrs shikha Verma,

Mrs. Suman Swami for their valuable time, precious guidance, kind,candid, wise and illuminatingadvise during training period.

I am also thankful to our instructors and other technical and non-technical staff for helping inunderstanding the various aspects and constructional details of work and site in 132 kv (Hybrid)

GSS SMS STADIUM ,JAIPUR.It may not be possible for me to acknowledge the contribution of all those who came forward to helpme. I express my sincere thanks to my colleges and and other trainees for their valuable ideas andsupport during practical training.It is a technical report of practical training at 132 kv (Hybrid)

GSS SMS STADIUM ,JAIPUR Rajasthan Rajya Vidyut Prasan Nigam Ltd. It wascommenced on 18-05-2015 and completed 10-07-2015. It was of 54 days and taken at 132 kv

(Hybrid) GSS SMS STADIUM, JAIPURI feel immense pleasure in conveying my heartiest thanks and deep sense of gratitude to Mr.

Vikas Gupta, HoD Electrical Engineering Department at Malaviya National Institute ofTechnology, Jaipur for his efforts and for technical as well as moral supprt. I feel indebted toexpress my heartiest thanks and gratitude to Mr. Anurag Vats(AEN), Mrs. kusum lata,Mrsshikha Verma, Mrs. Suman Swami for their valuable time, precious guidance, kind,candid,

wise and illuminating advise during training period.I am also thankful to our instructors and other technical and non-technical staff for helpingin understanding the various aspects and constructional details of work and site in 132 kv

(Hybrid) GSS SMS STADIUM ,JAIPUR.It may not be possible for me to acknowledge the contribution of all those who came forward

to help me. I express my sincere thanks to my colleges and and other trainees for theirvaluable ideas and support during practical training.

Contents

1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.1 First ideas 7

1.2 Location 7

1.3 Equipments Installed at GSS 7

1.4 Feeders 81.4.1 Incoming Feeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.4.2 Outgoing Feeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2 Single line diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.1 GIS 10

3 Description of Equipment Installed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.1 Lightening Areestor 113.1.1 ROD GAP ARRESTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.1.2 VALVE TYPE ARRESTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.1.3 ELECTROLYTIC ARRESTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1.4 THYRITE TYPE ARRESTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.2 Capacitive voltage Transformer 12

3.3 Wave Trap 13

3.4 Insulator 14

3.5 Isolator 14

4

3.6 PASS 153.6.1 Advantage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.6.2 comphonent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.6.3 GAS DENSITY CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.6.4 VOLTAGE TRANSFORMER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.6.5 COMBINED DISCONNECTOR /EARTHING SWITCH . . . . . . . . . . . . . . . . . . . . . . . . 163.6.6 OVER –PRESSURE RELIEF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.6.7 SF6 GAS INSULATED SYSTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.6.8 CIRCUIT BREAKER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.6.9 CURRENT TRANSFORMER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.6.10 BUSHING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.6.11 CB DRIVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.7 Intrument Transformers 173.7.1 Current Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.7.2 Potential Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.8 Circuit Breaker 17

3.9 Bus Bar 17

3.10 Power Transformer 18

3.11 PLCC 18

3.12 Battery Room 19

3.13 Relays 193.13.1 Functions of Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.14 Voltmeter 203.14.1 classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.15 Ammeter 203.15.1 classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4 Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4.1 Relays 224.1.1 USES OF RELAYS IN DIFFERENT PROTECTION SCHEMES . . . . . . . . . . . . . . . . . . . . . 224.1.2 protection used for Power Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234.1.3 protection for transmission line feeder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.2 Fire 23

5 Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5.1 Cables 245.1.1 Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.1.2 Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5

5.2 SCADA 24

5.3 Towers 25

1. Overview

1.1 First ideas132kv GSS(Hybrid) Sms substation is main power substation for power supply in Jaipur city and thesub-urbs.

Totel Capacity-2*50 MVAArea Required- 2100 sq.meter (In conventional type for same power area required is 25000 sq.

meter)145kv Hybrid Module and 36 Kv GIS is installed.India’s first Hybrid substation.Digital communication system and SCADA system is installed.Totel cost -28.31 crore .

1.2 LocationMostly the power houses are located on the outskirts of the city. Following this pattern 132kvGSS(Hybrid) Sms substation is located at 132kv GSS(Hybrid) Sms substation,Jaipur ,Rajasthan

1.3 Equipments Installed at GSS• Auto transformer 50MVA-2 units.• Lightening Arrestor 132 kV and 33 kv• PASS• GIS• Capacitive voltage Transformer• Wave trap• Isolator• Bus Bars• PLCC• Relays

1.4 Feeders 8

1.4 Feeders1.4.1 Incoming Feeders

• 132kv sanganer• 132kv mansarovar

1.4.2 Outgoing Feeders• 33kv Gautam Nagar• 33kv Stadium• 33kv Vidhanshabha• 33kv Secretiate• 33kv Ramniwas Bhag• 33kv Bisalpur• 33kv Station Trans.

2. Single line diagram

Single line diagram of Sms Substation

2.1 GIS 10

2.1 GISSuperior Dielectric Gas A gas-insulated substation (GIS) uses a superior dielectric gas, SF6, atmoderate pressure for phase-tophase and phase-to-ground insulation. The high voltage conductors,circuit breaker interrupters, switches, current transformers, and voltage transformers are in SF6 gasinside grounded metal enclosures. The atmospheric air insulation used in a conventional, air-insulatedsubstation (AIS) requires meters of air insulation to do what SF6 can do in centimeters.

GIS can therefore be smaller than AIS by up to a factor of 10. A GIS is mostly used where spaceis expensive or not available. In a GIS the active parts are protected from the deterioration fromexposure to atmospheric air, moisture, contamination, etc.

As a result, GIS is more reliable and requires less maintenance than AIS.GIS was first developed in various countries between 1968 and 1972. After about 5 years of

experience, the use rate increased to about 20 percent of new substations in countries where space islimited. In other countries with space easily available, the higher cost of GIS relative to AIS haslimited use to special cases.

For example, in the U.S., only about 2 percent of new substations are GIS. International experi-ence with GIS is described in a series of CIGRE papers (CIGRE, 1992; 1994; 1982).

3. Description of Equipment Installed

3.1 Lightening Areestor

They are con-nected in parallel with lines to limit the electrical voltage surges. Under normal voltage operationsit is open circuit and over voltage condition it is short circuited. A ring type structure is used toincrease the surface area so that the capacity to absorb the high voltage surges is increased. Thevarious types of lightening arrestors are used.

3.1.1 ROD GAP ARRESTERThis is the simplest form of LA consisting of two 12 mm dia. Or square with ends facing each other,one connected to line and the second connected to earth. These are usually connected across thebushings of various equipments.

3.1.2 VALVE TYPE ARRESTERIt is also called non-linear diverter. Such an arrester consists essentially of a divided spark gap inseries with a resistance element having non-linear characteristics.

3.2 Capacitive voltage Transformer 12

3.1.3 ELECTROLYTIC ARRESTERIt is the earliest type of arrester with a large discharge capacity. It operates on the fact that a thin filmof aluminium hydroxide deposited on the aluminium plate immersed in electrolyte acts as a highresistance to a low voltage but a low resistance to a voltage above a critical value.

3.1.4 THYRITE TYPE ARRESTERLightening arrestor are provided between the line and earth provided theprotection against travelingwave surge the THRITE lightening arrestor are provided at GSS. This type of LA has a basic cellmade of thirties, which is a particular type of clay, mixed with Carborendum. Thirties has a particularproperty of being insulator one voltage.

Punctured the Thyrite type arrestor will discharge several thousands ampere without the slightesttendency of flashover on the edges of most important of the advance is that there is absolutely notime lag in its performance.

3.2 Capacitive voltage Transformer

Capacitive voltage transform-ers are special kind of power transformers using capacitors to step down the voltage.The capacitivevoltage transformer comprises of a capacitor divider with its associated electromagnetic unit. Thedivider provides an accurate proportioned voltage, while the magnetic unit transforms this voltage,in both magnitude and phase to convenient levels suitable for measuring, metering, protection etc.All WSI capacitor units have metallic bellows to compensate the volumetric expansion of oil inside.The porcelain in multi unit stack, all the potential points are electrically tied and suitably shielded toovercome the effect of corona etc. Capacitive voltage transformers are available for system voltagesof 33KV to 420KV.

3.3 Wave Trap 13

3.3 Wave Trap

A device used to exclude unwanted fre-quency components such as noise or the interference of a wave is called wave trap. It is an essentialinstrument used for tripping of the wave. It shapes like a drum. It is connected to the maon incomingfeeder sothat it can trap th waves whic may be danger to the instrument in the substation. There arecoils of inductance 2mH to 2 H rated for full line currents and suitably insulated for high voltagesand are often refered as wave trap or line choke coils. They are placed in series with with powerlines and offer high impedence to carrier frequency, but pass 50 Hz power frequency easily. Standardsize wave traps are rated for 500,800 and 1200 amperes. They can be resonated at single carriercapacitors. These tuning capacitoos are protected against the surge voltage by a spark gap arranged inparallel. The parallel resonance circuit is clamped with a suitable resistsnce to produce a differencein the blocking range of frequency which improves the quality of the transmission. Instead of timingat one or two carrier frequency wide band operation is also used which makes the wave trap effectiveas more than one channel.

3.4 Insulator 14

3.4 Insulator

3.5 IsolatorIsolator is also known as disconnector. It operats under no load condition. It doesn’t have anyspecified current breaking capacity. They are not eevn used for breaking load currents. Circitbreakers make and break connections unser normal current or short circuit conditions. Isolators areused in addition to circuit breaker and provided on each side of every circuit breakers to provideisolation and enable maintancne. While opening a circuit, circuit breaker os opened first then theisloators while closing a circuit, isolator is closed first then circuit. They are necessary on supplyside of circuit braeker in order to ensure isloation of the circuit breaker from live parts from themaintannce purpose automatic switching of isloators is preferred.

isolators that was used in plant is of single break,horizontal double earthed type.It is a two poleisolators.the 2 pole isolators have to identical poles or 3 insulators ports mounted on a fabricatedsupport. the conducting aluminium rod,fixed and moving contacts during the opening operation theconducting rods swing apart and isolation is obtained.Three types of isolators are installed at SMSSubstation.

• Bus Isolator• Line Isolator• Earth Isolator

3.6 PASS 15

3.6 PASS

(PASS AND SWITCHSYSTEM) The term hybrid refer to the combination of both conventional of both conventional airinsulated switchgear (AIS) and the newer SF6 metal –clad insulated switchgear(GIS) ,which takeadvantage of the two different technology . The hybrid switchgear solution uses already existing,tried-and tested gas insulated switching component but also a conventional and very reliable AISbus to connect the various hybrid modules. All the functions(except the ring type current transformer)are sealed in a single SF6gas insulated housing.

• Circuit breaker• Disconnectors• Earth switch• Cable sealing switches• SF6 VTs or voltage sensor• Control and protection cabinet

PASS could also be called “performance and save space” as any substation layout can be obtainedby making efficient use of available space .

3.6.1 AdvantagePASS combine all the typical function of a complete AIS for electrical substation with voltage ratingof up to 245 kv in a unit whose volume is comparable to that of a conventional circuit-breaker ofequal class.

It takes advantages and widens the scope of the operation philosophy of the PASS series whosedominating factors, those that have dictated the product’s success with more than 2000 systems soldthroughout the world ,is briefly outlined below

• Relatively inexpensive AIS busbar• All live contacts in SF6• Fewer switching element• Pre tested in factory also for earthquake.• Competitive installation cost.• High degree of factory assembly.• Facilitates monitoring /on line diagnostics

3.6 PASS 16

• Modularization of the substationThat means – - Very high reliability and availability of substation - Drastic reduction in the timeneeded to install the equipment - Much less space required - Simplified substation layout - Lessmaintenance required - Very good cost performance for purchasing ,maintenance,operationandrelocation Component

3.6.2 comphonent3.6.3 GAS DENSITY CONTROL

Each PASS pole has a single gas compartment .Since the dielectric strength of the switchgear andthe capacity of the SF6circuit breaker depend on the SF6 gas ,gas density relay is installed to thecontrol gas density and detect leakage.

3.6.4 VOLTAGE TRANSFORMERPASS can be equipped with a conventional GIS inductive voltage transformer .Similarly to currenttransformer ,several combination of windings for protection and measurement with different loadsare available.

3.6.5 COMBINED DISCONNECTOR /EARTHING SWITCHPASS is equipped with combined disconnecter /earthing switch. The mechanism has a minimalnumber of mechanical components and is intrinsically reliable,and maintenance free.All combinationare possible. In all PASS version ,the combined disconnector/earthing switch is mechanically coupledto the shaft.The disconnector/earthing switch may , in an emergency , be operated manually bymeans of a crank.

3.6.6 OVER –PRESSURE RELIEFA rupture diaphragm(rupture disk) is installed to protect against excessive over pressure due tointernal arc faults. When a predetermined overpressure is reached ,the rupture disk will break andrelieve the pressure which would otherwise cause the enclosure itself to break .Defectors in front ofthe diaphragms ensure the safety of personel.

3.6.7 SF6 GAS INSULATED SYSTEThe compact design of the PASS module is due to the excellent insulation quality of SF6 gas .Itsdielectric strength is homogeneous field is about 2.5 times greater than that of air at the sametemperature and pressure . The design of the live components is such that the field distribution is anhomogeneous as possible , which allows the intrinsic strength of insulating gas to be utilized moreefficiently .

3.6.8 CIRCUIT BREAKERThe PASS circuit breaker is a single pressure interrupter that operate by means of well knownselfblastprinciple . The energy for interrupting current is partly supplied by the arc itself , therebyreducing the energy the operating mechanism must provide by about 50 percent as compared to aconventional puffer – type circuit breaker.

3.7 Intrument Transformers 17

3.6.9 CURRENT TRANSFORMERPASS is equipped with a conventional current transformer , to meet the customers requirement , e.g.for retrofitting .Several combination of cores for protection and measurement with different loadsare available .Up to 5crore can be fitted into the current transformer .

3.6.10 BUSHINGThe insulator consist of an epoxy impregnated fibreless tube with siliconrubber . The main featureare:

• high degree of safety(crank and explosion resistant)• low weight• excellent pollution and rain performance• sandstorm resistant• maintenance free

3.6.11 CB DRIVEBLK is the spring operated drive for the circuitbreaker ,designed with aminimum number of compo-nents. BLK is available with 2 alternatives: -BLK 82 intended for a single pole operation in line–bays where single phase autoreclosing is foreseen - BLK 222intended for three pole operation

3.7 Intrument TransformersThe applications of transformers are put for measurement puposes the actual measurements is doneby measuring instruments. Tranformrs used in conjuction with measuring instruments are calledinstrument transformers.

3.7.1 Current TransformerThe trasformer used in measuremnt of current is called current transformer.In power system currentand volateges are very high so that their measuremet are not possible. The solution lies in steppingdown these currents and volatges by instument transformers.

Construcion of CTSeparately mounted past type CT are suitable for outdoor service. The primary conductor alwaysis at high voltage with respect to earth, hence it is insulated by means of insulator column feed bydielectric oil. the secondary of CT then completely wrapped by external tape with or without exteriorring ends and circumferential insulating wraps. Dielectric oil used as an insulating medium.

3.7.2 Potential TransformerCapacitive voltage transformer is mostly used as potential transformer.

3.8 Circuit Breaker

3.9 Bus BarThe Buses concerned with swith gear don’t have any wheels, not do they transprot people. However,they are called buses perhaps due to their commence that they transport electric current. The conductoto which several local feeders or sources are connected, were called buses. Now the conductors

3.10 Power Transformer 18

carrying haeavy currents are also called buses. Thes bars are of alumunium generally of rectangularcross section. At SMS Substation, their shapes are round hollow bars which is made of aluminium.Here aluminium is preffered over copper due to its advantages such as:

• higher cnductivity on weight basis• Lower cost of equal carrying capacity the current is same• excellent corrosion resistance

Two buses(132kV) PASS circuit breaker(SF6) scheme is used at Sms substation GSS.

3.10 Power TransformerThe transformer is a static apparatus, which receives power/energy at it, one circuit and transmits itto other circuit without changing the frequency. With this basic conception we can use the voltagesat our desired level while utilizing the power. As, the voltage used to generate at modern powerhouses at 11 KV or so and afterwards we get it step up at a level of 33 KV, 66 KV, 132 V, 220 KV or400 KV, 750 KV for transmission to minimize the distribution losses. Again we get it step downwith the help of transformer to use at our wishes at 11 KV, 6.6 KV or even 415, 230 volts at our

houses.

3.11 PLCCThe communication links are also needed for protection and tele control purpose .It is possibleto rent telephone lines from the P and T department for this purpose or have private cables forcommunication normarlly PLCC is used for the purpose. In this system of power line carriercommunication purpose are needed as the power line themselves provide a very good medium forcommunication.

Some drawbacks of PLCC system are:• Propercare has to be taken to guard carrier equipments and person using them against high

voltages and currents on the lines.• Reflections are produced on power line connected to high voltages lines.This increase attenua-

tion and create other problems.

3.12 Battery Room 19

• High voltage lines have transform connection which attenuate carrier current.Substationsequipments adversely affect the carrier currents.

• Noise introduced by power line is far more than in case of telephone lines,which is due todischarge across insulators corona and switching devices.

3.12 Battery RoomThere is a battery sexton or battery room which has 55 batteries of 1.2 volt each for 132KV sectionand 110 batteries for 33kv section. Therefore D.C. power available is for functioning of the controlpanels. A battery charger to charge the battery. • Various parts of lead acid batteries:-

• Plates• Separators• Electrolyte• Container• Terminal port• Vent plugs

Charging of batteries:- Initial charging-: It is the first charging given to batteries by which thepositive plates are converted to “lead peroxide”, where as the –ve plates will converted to spongylead. Also in a fully charged battery the electrolyte specific gravity will be at its highest venueor 1.2 and its terminal voltage will be 24 volts Discharging:- When a fully charged battery deliv-ers its energy out by meeting a load the lead peroxide of the +ve plates slowly gets converted tolead sulphate and the spongy lead of the –ve plates also gets converted into lead sulphate duringthis time the specific gravity of the electrolyte also decreases the value around 1.00 and the ter-minal voltage also decreases from its initial to a lower value which may be around 1.85 or 1.8.

3.13 RelaysIt is an electrical device designed to initiate isolation of a part of an installation, or to operate an alarmsignal, in the event of an abnormal condition or fault. It differs in normal and abnormal conditions,when any actuating quantity is increased from its preset value during fault conditions, it isolate thefaulty part from the healthy part as quickly. These actuating quantities may be voltage, current,

3.14 Voltmeter 20

power, frequency etc. Every electrical equipment needs portion the house wiring is protected by thefuses. Modern generators are protected by complex protective schemes. The choice of protectiondepends upon several aspects such as type and rating of protective equipments. The location ofrelay is very important the protective relay may protect the concerned equipment from the abnormaloperating condition develops in protective relaying of that equipment sense the abnormal conditionand initiates the alarm and close the trip circuit of CB and isolate the equipment from the supply.The relays are compact self-contained device, which respond to an abnormal condition wheneverand abnormal condition is developed. The relay close there contacts thereby the trip circuit ofCB is closed current from the battery supply flows in the trip circuit [coil] of breaker and breakeropens and the faulty part is disconnected from the supply. Besides relays and CB there are severalcomponents in relaying schemes these includes potential transformer protective fine relay time delayrelay auxiliary relay secondary circuit and accessories each equipment is important in protectionrelying in team work of their components.

3.13.1 Functions of Relays• To sound an alarm or close the trip coil of CB to disconnect the equipment in abnormal

condition, which includes overload under voltage temperature rise, unbalanced load reservepower under frequency short circuit.

• To disconnect the abnormally operating part to prevent subsequent fault as over load protectionof machine and prevent machine failure.

• To disconnect the faulty part if a machine is connecte4d immediately after a winding faultonly a few coil may need replacement.

• To realize the effect of fault by disconnecting faulty part from healthy part causing leastdisturbance to the healthy replacement.

• To disconnect the faulty part quickly to improve the system stability service condition andsystem performance.

.

3.14 VoltmeterA voltmeter is an instrument used to measure voltage. For instance, a voltmeter can be used to see ifthere is more electricity left in a battery.

3.14.1 classificationAnalog type

• Moving Iron type (For AC measurements)• PMMC type (For DC measurements)

Digital voltmeter.

3.15 AmmeterAn ammeter is a measuring instrument used to measure the electric current in a circuit. Electriccurrents are measured in amperes (A), hence the name.

3.15.1 classificationAnalog type

3.15 Ammeter 21

• Moving Iron type (For AC measurements)• PMMC type (For DC measurements)

Digital Ammeter.Now a days digital multimeters are used for voltage ,current, and power measurements.

4. Protection

The following are consequences of faults.• Abnormally large currentsflow in parts of the system with associated overheating of compho-

nents.• System voltages will be off their normal acceptable levels ,resulting in possible equipment

damage.• parts of the system will be caused to operate as unbalanced 3- phase systems,which will mean

improper operation of equipment.A number of requirements for protective systems provide the basis of design criteria.

• Reliability• Speed• Selectivity• Smplicity and ecomnomy

4.1 RelaysDifferent types of Relays are used for protection as :

• Current relays• Voltage relays• Power relays• Directional relays• differential relays• Distance relays

4.1.1 USES OF RELAYS IN DIFFERENT PROTECTION SCHEMES:-

• Power transformer.• Transmission line feeder.• Bus bars.

4.2 Fire 23

• Shunt capacitor banks.

4.1.2 protection used for Power Transformer• Buccholz relay protection• differential protection• Pressure release device(PRD)• oil surge relay protection• Back up protection• WTP(winding temperature protection)• OTP(oil temperature protection)• over flux protection• fire fighting protection

4.1.3 protection for transmission line feeder• differential back up protection• differntial relay protection.

4.2 Fire

5. Miscellaneous

5.1 CablesSince the loads having the trends towards growing density. This requires the better appearance,rugged construction, greater service reliability and increased safety. An underground cable essentiallyconsists of one or more conductors covered with suitable insulation and surrounded by a protectingcover. The interference from external disturbances like storms, lightening, ice, trees etc. should bereduced to achieve trouble free service. The cables may be buried directly in the ground, or may beinstalled in ducts buried in the ground.

5.1.1 Advantages• Better general appearance• Less liable to damage through storms or lighting• Low maintenance cost• Less chances of faults• Small voltage drops

5.1.2 DisadvantagesThe major drawback is that they have greater installation cost and introduce insulation problems athigh voltages compared with equivalent overhead system.

5.2 SCADASCADA (supervisory control and data acquisition) is a system operating with coded signals overcommunication channels so as to provide control of remote equipment (using typically one commu-nication channel per remote station). The control system may be combined with a data acquisitionsystem by adding the use of coded signals over communication channels to acquire informationabout the status of the remote equipment for display or for recording functions.

5.3 Towers 25

SCADA can be a great tool while working in an environment where operational duties needto be monitored through electronic communication instead of locally. For example, an opera-tor can position a valve to open or close through SCADA without leaving the control stationor the computer. The SCADA system also can switch a pump or motor on or off and has thecapability of putting motors on a Hand operating status, Off, or Automatic. Hand refers to oper-ating the equipment locally, while Automatic has the equipment operate according to set pointsthe operator provides on a computer that can communicate with the equipment through SCADA.

5.3 TowersAt GIS substation lines are incoming so electrical poles are designed for that ,should be capableto withstand with high voltages. An overhead power line is a structure used in electric powertransmission and distribution to transmit electrical energy along large distances. It consists of one ormore conductors (commonly multiples of three) suspended by towers or poles. Since most of theinsulation is provided by air, overhead power lines are generally the lowest-cost method of powertransmission for large quantities of electric energy. Towers for support of the lines are made ofwood (as-grown or laminated), steel (either lattice structures or tubular poles), concrete, aluminum,and occasionally reinforced plastics. The bare wire conductors on the line are generally made ofaluminum (either plain or reinforced with steel, or composite materials such as carbon and glass fiber),though some copper wires are used in medium-voltage distribution and low-voltage connections tocustomer premises. A major goal of overhead power line design is to maintain adequate clearancebetween energized conductors and the ground so as to prevent dangerous contact with the line, andto provide reliable support for the conductors, resilient to storms, ice load, earthquakes and otherpotential causes of damage.[1] Today overhead lines are routinely operated at voltages exceeding765,000 volts between conductors, with even higher voltages possible in some cases.