66 kv Substation Report File

SIX WEEK INDUSTRIAL TRAINING REPORT ON 66KV SUB-STATION

TRANING ON PSPCL

SUBMITTED BY :-

SUBMITTED TO :-

MR. NAVDEEP SINGH

ELECTRICAL ENGINEERING

ELECTRICAL ENGINEERING

DEPARTMENT

UNI. ROLL NO. :- 1404346

BGIET SANGRUR

Campus :- Main Patiala Road, Sangrur. 148001 www.bgiet.ac.in e-mail : [email protected]. In

INDUSTRIAL TRAINING REPORT ON 66 KV SUB-STATION AT PUNJAB STATE POWER CORPORATION LTD.

NAME :-

MR. NAVDEEP SINGH

BRANCH :-

ELECTRICAL ENGINEERING

UNIVERSITY ROLL NUMBER :-

1404346

SESSION :-

2013 - 2017

TRAINING AT :-

PSPCL

TRAINING ON :-

66KV SUB-STATION

DATE :-

FROM 01/06/2015 TO 15/07/2015

Campus :- Main Patiala Road, Sangrur. 148001 www.bgiet.ac.in e-mail : [email protected]. in

1

CONTENTS TOPIC’S

PAGE NO.

1.

ACKNOWLEDGEMENT

3

2.

BIBLIOGRAPHY

5

3.

SUB-STATION

4.

ELETRICAL INSTRUMENTS

5.

TRANSFORMER

6.

PARTS OF TRANSFORMER

14-16

7.

CURRENT TRANSFORMER

17-18

8.

POTENTIAL TRANSFORMER

19-22

9.

CAPACITOR BANK

6-7 8 9-13

23

10. 11KV INCOMING INDOOR

24

11. CONTROL PANNEL

25-26

12. BUS BARS

27-28

13. CIRCUIT BREAKER

29-31

14. LIGHTNING ARRESTER

32-33

15. POWER-LINE COMMUNICATION

34

16. ELECTRICAL ISOLATOR

35-36

17. ELECTRICAL INSULATOR

37-38

18. BATTERY ROOM

39

19. OVER CURRENT RELAY

40

20. EARTH FAULT REALY

41-42

21. TOOLS USE IN ELECTRICAL

43-47

2

ACKNOWLEDGEMENT

Nothing

cocrte

can

be

achieved

without

an

optimum

combination of instection and perspiration I owe a lot to many for instiration path. But thinking people who have contributed to a training of a train we is a little like saying thanks at the academy awards.

I wish expess my sincere sense of gratitude to ‘Mr. Simerpreet singh’ (HOD/EE) for permtting me to conduct industrial training in an esteemed organization :PUNJAB STATE CORPORATION LTD. I wish to express of gratitude to my training incharge ‘Er kulwant singh’ for his undaunted guidance and constant encouragement at all the stages of my training I carried out under him. Last but not the least, I express my sicer gratitude to my faculty members, my family member who have taken great pains to enable me to reach up to this status of life.

THANK YOU

3

BIBLIOGRAPHY 

Training manuals



www.google.com



www.wikipedia.com



www.pspcl.com



www.tech-faq.com



www.Electricalengg.com



www.pseb.com

4

SUB STATION Sub-station serve as sources of energy supply for the local areas of distribution in which these are located. Their main functions are to receive energy transmitted at high voltage from the generating station receive energy transmitted at high voltage from the generating station reduce te voltage to a value appropriate for local distribution and provide faculties for switching. A sub-station is convenient place for installing synchronous condensers at the end of the transmission line for purpose of improving power factor and make measurements to check the operation ao the various parts of the power system street lighting equipment as well as switching controls for street lights can be insarlled in a sub-station.

Classifications 1. On the basis of nature of duty :o Step-up or primary sub-station :- These are the substation where form power is transmitted to various load centers in the system network. o Step-up & step-down or secondery sub-station:Sub-station

of

this

type

may

be

located

at

generating points where from power is fed directly to the loads and balance power generated is transmitted to the network for transmission to other load centers. 5

o Step-down or distribution sub-station:- Such substation receive power from secodary sub-station at extra high voltage and step down its voltage for secondary distribution. 2. On the basis of operating voltage :o

High

voltage

sub-stations

involving

voltage

between 11KV &66KV. o

Extra high voltage substations involving voltages

between 132KV & 400KV. o

Ultra high voltage sub-station operation on voltage

above 400KV. 3. On the basis of importance’s:o Grid sub-station:- These are the sub-station form where bulk power is transmitted form one point to another point in the grid. These are important because any distribution in these sub-station may cause the failure of grid. o Town sub-station:- These sub-station are EHV substation, which step down the voltage at 33/11KV for further sub-station results in the failure of supply for whole of the town.

6

4. ON the basic of design:o In

door

type

sub-station:-In

such

sub-staion

the

apparatus is installed with in the sub-station bulding. Such sub-station are usually for a voltage up to 11KV but can be erected for the 33KV to 66KV when the surrounding

atmosphere

is

contaminated

with

impurities such as metal corrading gases and fumes conductive dust etc. o Out door type sub-station:- These sub-sation are futher subdivided into:-pole mounted sub-station :-such substation

are

erected

for

distribution

of

power

in

localities. Single stout pole H-pole & 4-pole structures with suitable platforms are employed for transformers capacity up to 25KV,100KVA and 100KV respectively. o Foundation mounted sub-station :-For transformer of capacity above 250KVA the transformer are too heavy for pole mounting. Such sub-station are usually for voltage of 33000V & above. o Selection and location of site :a. Type of sub-station b. Available of suitable and sufficient land c. Communication facility d. Atmospheric pollution

7

INSTRUMENTS USE IN 66KV SUB-STATION 

TRANSFORMER



CURRENT TRANSFORMER



POTENTIAL TRANSFORMER



WAVE TRAP



LIGHTING ARRESTER



ELECTRIC ISOLATER



BUS BARS



BUS COUPLER



CIRCUIT BREAKER



CONTROL PANEL



POWER LINE COMMUNICATION



EARTH FAULT RELAY



ON LOAD TAP CHARGER



CAPACITOR BANK



BATTERYS

8

TRANSFORMER Power transformer is the main electrical used in the substation for changing the voltage from that of incoming supply so that of outgoing distribution feeder. The winding are placed in the oil tank and immersed in the transformer oil for cooling the winding by circulating oil. The power transformer is used for step up or step down, voltage. The supply circuited is connected to the terminal of primary winding

and

outgoing

distribution

feeder

terminals

are

connected to secondary winding through insulator bushing mounted on the side of transformer. In 66KV/11KV sub-station, Nabha two power transformer are used.

The

primary

and

secondary

winding

of

these

transformers connect in star-star connection. In this substation 66KV/11KV transformer are used, two transformers are use in there T1 & T2. The capacities of these transformers are T1 is 20MVA & T2 is 31MVA The principle parts of a transformer and their functions are: 

The core, which makes a path for the magnetic flux.



The primary coil, which receives energy from the ac source.



The secondary coil, which receives energy from the primary winding and delivers it to the load.



The enclosure, which protects the transformer from dirt, moisture, and mechanical damage.

9

Fig.1. Transformer

Specification T1 Capacity

………………………………………

20MVA

Phases

………………………………………

3

Frequency

………………………………………

50HZ

Connections

………………………………………

*-* conn.

Voltage

..…………..

66KV

Voltage

….………..

LV side

Max. current

…..………

HV side …………

Max. current

…………

HV side ……….

LV sid

10

………

………..

11KV 174.95A 1049.75A

Transformer core:The composition of a transformer core depends on voltage, current, and frequency. Commonly used core materials are air, soft iron, and steel. Each of these materials is suitable for certain applications. Generally, air-core transformers are used when the voltage source has a high frequency (above 20 kHz). Iron-core transformers are usually used when the source frequency is low (below 20 kHz). • A soft-iron-core transformer is very useful where the transformer must be physically small, yet efficient. The iron-core transformer provides

better

power

transfer

than

does

the

air-core

transformer. A transformer whose core is constructed of laminated sheets of steel dissipates heat readily; thus it provides for the efficient transfer of power. • The majority of transformers contain laminated-steel cores. These steel laminations are insulated with a non conducting material, such as varnish, and then formed into a core. It takes about 40 laminations to make a core of 2 cm thick. The purpose of the laminations is to reduce losses which will be discussed later in this chapter. • The most efficient transformer core is one that offers the best path for the most lines of flux with the least loss in magnetic and electrical energy.

11

Ideal Transformer

Fig. 2 Ideal Transformer

Center-tapped Transformer

Fig.3 Center-tapped Transformer

12

Applications of Transformers 

Transformers

have

many

applications

in

power

transmission and electronics: 

They may be used to minimise energy losses due to voltage

drop

in

transmitting

electricity

over

long

distances. 

They match loads with internal resistance so that there is maximum power transfer.



They couple signals between electronic stages.

Losses in Transformers All transformers have copper and core losses, and flux leakage. Copper loss is ohmic power lost in the primary and secondary

windings

of

atransformer

due

to

the

ohmic

resistance of the windings. Copper loss, in watts, may be found using the following equation

Copper Losses = Ip Rp + Is Rs Where, Ip is the primay current, Is is the secondary current, Rp is theprimary resistance, and Rs is the secondary resistance.

Core losses are caused by two factors: hysteresis and eddy current losses. Hysteresis loss is that energy lost by reversing the magnetic field in the core as the magnetizing AC rises and falls and reverses direction. Eddy current loss is a result of induced currents circulating in the iron core. It can be used by laminations! 13

PARTS OF TRANSFORMER 

Conservater :-

Fig.4 Conservater

It is used generally to conserve the insulating properties of the oil from deterioration and protect the transformer against faliur on account of bad auality of oil. These are also sometimes known as expansion vassel meant for provided adequate space for expansion of oil than abient temperature changes. It is a small tank. The main tank is completely filled with transformer oil but conservator partically filled with transformer oil 

Bushings :- Bushing are made for highly insulating material to insulate and to bring out

the terminals of the

transformer form the container. 

Oil Gagul :- Every transformer is provided with on oil gague to indicate the oil level.

14



Breather :-

Fig.5 Breather

The breather is used to prevent entey of moisture is used to prevent entry of moisture inside the transformer tank. The breather constant of silica gel. When air is taken in ao take out of the transformer due to contraction or expension of oil in tank the silica gel absorbs moisture and allows the air free from moisture and allow the free from moisture to enter the transformer 

Buchholz Relay :-

Fig.6 Buchholz Relay

It’s a gas actuated relay used for protecting oil immersed transformer against all type of faults. This relay installed in the pipe connecting the conservator to the main tank. 15

The buchholz relay consist of an oil tight container

with

mercury switch. One of the mercury switch is attached to the upper float which close the alarm circuit. 

Radiators :-

Fig.7 Radiators

In large capacity transformer radiators are used for cooling. When an electrical transformer is loaded, the current starts flowing through it’s windings. Due to this flowing of electric current, heat is produced in the windings, this heat ultimately rises the temperature of transformer oil. We know that the rating of any electrical equipment depends upon its allowable temperature rise limit. Hence, if the temperature rise of the transformer insulating oil is controlled, the capacity or rating of transformer can be extended up to significant range.

16

CURRENT TRANSFORMER

A current transformer (CT) is used for measurement of alternating electric current. Current transformers, together with voltage (or potential) transformers (VT or PT), are known as instrument transformers

Fig. 8 Current transformer

. When current in a circuit is too high to apply directly to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments. A current transformer isolates the measuring instruments from what may be very high voltage in the monitored circuit. Current transformers are commonly used in metering and protective relays in the electrical power industry. 17

Design

Fig. 9 Basic operation of current transformer

Current transformer is used for measur of current in line. The primary winding is connected in series with line carrying the current to be measured. The primary winding consist of very few turns and, due to this. Ther is no appreciable voltage drop across it. The secondary winding of the CT has a large number of turn and the exxact number of turn can be determined by the turn ratio. The ammeter current coils are connected directly across the secondary nearly under short circuit conditions. One of the secondery winding is earthed so as to protected equipment and personal in case of insulation breakdown in the current transformer. Transformer capacity = 20MVA H.V. Max current

66KV 174.95A

L.V. Max current

11KV 1049.73A

So, NOTE: Above 11000V current divided by 1A & upto 11000V current divided by 5A.

18

POTENTIAL TRANSFORMER Potential Transformer is basicaly step down transformer. Potential transformer are used to operates potential coils of wattmeter, relay and voltmetre for high voltage line.

Fig.10 Potential Transformer

A voltage transformer theory or potential transformer theory is just like a theory of general purpose step down transformer. Primary of this transformer is connected across the phase and ground. Just like the transformer used for stepping down purpose, potential transformer i.e. PT has lower turns winding at its secondary. The system voltage is applied across the terminals of primary winding of that transformer, and then proportionate

secondary

voltage

secondary terminals of the PT. 19

appears

across

the

The secondary voltage of the PT is generally 110 V. In an ideal potential transformer or voltage transformer, when rated burden gets connected across the secondary; the ratio of primary and secondary voltages of transformer is equal to the turns ratio and furthermore, the two terminal voltages are in precise

phase

opposite

to

each

other.

But

in

actual

transformer, there must be an error in the voltage ratio as well as in the phase angle between primary and secondary voltages. The errors in potential transformer or voltage transformer can be best explained by phasor diagram, and this is the main part of potential transformer theory.

Fig. 11 Phasor diagram 20

Is - Secondary current. Es - Secondary induced emf. Vs Secondary

terminal

voltage.

Rs

-

Secondary

winding

resistance. Xs - Secondary winding reactance. Ip - Primary current. Ep - Primary induced emf. Vp - Primary terminal voltage. Rp - Primary winding resistance. Xp - Primary winding reactance. KT - Turns ratio = Numbers of primary turns/number of secondary turns. I0 - Excitation current. Im - Magnetizing component of I0. Iw - Core loss component of I0. Φm - Main flux. β - Phase angle error. As in the case of current transformer and other purpose electrical power transformer, total primary current Ip is the vector sum of excitation current and the current equal to reversal of secondary current multiplied by the ratio 1/KT. Hence,Ip = I0 + Is/KT If Vp is the system voltage applied to the primary of the PT, then voltage drops due to resistance and reactance of primary winding due to primary current Ip will come into picture. After subtracting this voltage drop from Vp, Ep will appear across the primary terminals. This Ep is equal to primary induced emf. This primary emf will transform to the secondary winding by mutual induction and transformed emf is Es. Again this Es will be dropped by secondary winding resistance and reactance, and resultant will actually appear across the burden terminals and it is denoted as Vs.

21

So, if system voltage is Vp, ideally Vp/KT should be the secondary voltage of PT, but in reality; actual secondary voltage of PT is Vs. Voltage Error or Ratio Error in Potential Transformer (PT) or Voltage Transformer (VT) The difference between the ideal value Vp/KT and actual value Vs is the voltage error or ratio error in a potential transformer, it can be expressed as,

Phase Error or Phase Angle Error in Potential or Voltage Transformer The angle ′β′ between the primary system voltage V p and the reversed secondary voltage vectors KT.Vs is the phase error. Cause of Error in Potential Transformer The

voltage

applied

to

the

primary

of

the

potential

transformer first drops due to the internal impedance of the primary. Then it appears across the primary winding and then transformed proportionally to its turns ratio, to the secondary winding. This transformed voltage across the secondary winding will again drop due to the internal impedance of the secondary, before appearing across burden terminals. This is the reason of errors in potential transformer.

22

CAPACITOR BANK A capacitor bank is a grouping of several identical capacitors interconnected in parallel or in series with one another. These groups

of

capacitors

are

typically

used

to

correct

or

counteract undesirable characteristics, such as power factor lag or phase shifts inherent in alternating current (AC) electrical power supplies. Capacitor banks may also be used in direct current (DC) power supplies to increase stored energy and improve the ripple current capacity of the power supply.

Fig.18 Capacitor Bank

Single capacitors are electrical or electronic components which store electrical energy. Capacitors consist of two conductors that are separated by an insulating material or dielectric. When an electrical current is passed through the conductor pair, a static electric field develops in the dielectric which represents the stored energy. Unlike batteries, this stored energy is not maintained indefinitely. 23

11KV INCOMING INDOOR After stepped down 66KV into 11KV by power transformer the secondary outputt is connected in three types with incomer panel. There are two incoming panel. One is connected with transformer T1 and second T2. There three type and its name.  Metering core : All meter are connected to metering core.  Protection core : All the protection relays connected to the protection core eg. Over current relay , Earth fault relay  Differential

core:

differential

relay

is

connected

with

differential core. This relay is tripped when the load is unbalance.

Fig.19. 11 KV Incoming

24

CONTROL PANNEL Control pannel boards are also called distribution boards. In the back side of the transformer 3 bus bars placed. All the pannel boards are connected in parallel through bus bars. In these control pannel various equipment are used e.g 

Trolly



Over current relay



Earth faul relay



Sensitive relay



Spring



Digital energy meter



Indicating lamps

To distribute power take a handle and find the spring charge hole. After find hole, adjust handle and rotate it and clock-wise direction. when the indicating lamps show the spring charged, then operate the ON handle. If any fault in line, then feeder cut off supply automatically with the help of ‘over current relay & earth fault’

25

Fig. 12 Control pannel

In sub-station every control pannel has five indicating lamps. o

White lamp cheack the healthy dc input voltage.

o

Blue indicating lamp tell the spring is chared

o

Yellow indicating lamp tell us circuit tripping.

o

Red indicating lamp show that feeder is ON position.

o

Green indicating lamp show that feeder in OFF position.

26

BUS BARS In electrical power distribution, a bus bar is a metallic strip or bar (typically copper, brass or aluminum) that conducts electricity within a switchboard, distribution board, substation, battery bank, or other electrical apparatus. Its main purpose is to conduct a substantial current of electricity, and not to function as a structural member. The material composition and cross-sectional size of the busbar determine the maximum amount of current that can be safely carried. Busbars can have a cross-sectional area of as little as 10 square millimetres (0.016 sq in), but electrical substations may use metal tubes 50 millimetres (2.0 in) in diameter (20 square millimetres (0.031 sq in)) or more as busbars.

Fig. 12 Bus bar

27

Design and placement Busbars are produced in a variety of shapes such as flat strips, solid bars and rods, solid or hollow tubes, and braided wire. Some of these shapes allow heat to dissipate more efficiently due to their high surface area to cross-sectional area ratio. The skin effect makes 50–60 Hz AC busbars more than about 8 millimetres (0.31 in) thickness inefficient, so hollow

or

flat

shapes

are

prevalent

in

higher

current

applications. A hollow section also has higher stiffness than a solid rod of equivalent current-carrying capacity, which allows a greater span between busbar supports in outdoor electrical switchyards.

28

CIRCUIT BREAKER A circuit breaker is an 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.

fig. 13 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 or high voltages are usually arranged with protective relay pilot devices to 29

sense a fault condition and to operate the trip opening mechanism. The trip solenoid that releases the latch is usually energized by a separate battery, although some high-voltage circuit breakers are self-contained with current transformers, protective relays and an internal control power source.

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 chambers)



Division into partial arcs



Zero point quenching)



Connecting capacitors in parallel with contacts in DC circuits.

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

30

Tests All routine tests shall be carried out as per the latest applicable standards on the breaker and its accessories. Certificates of tests on bought out items such as bushings shall be furnished for approval.

Type tests, if specified and routine tests shall also be carried out on all associated equipment as per relevant standards.

In addition to the routine tests, the following tests shall be performed on each breaker:

a) Lightning impulse withstand test b) Radio Interference Voltage Test (for 66kV Breakers)

Speed curves for each breaker shall be obtained with the help of a suitable Operation Analyzer to determine breaker contact movement during opening, closing, auto-recessing and trip free operation under normal as well as limiting operating conditions The tests shall show the speed of contacts at various stages of operation, travel of contacts, opening time, closing time, shortest time between separation and meeting of contacts at break-make operation, etc.

31

LIGHTNING ARRESTER A lightning arrester is a device used on electrical power systems and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of lightning. The typical lightning arrester has a highvoltage terminal and a ground terminal. When a lightning surge (or switching surge, which is very similar) travels along the power line to the arrester, the current from the surge is diverted through the arrestor, in most cases to earth.

Fig. 14 Lighting Arrester

In telegraphy and telephony, a lightning arrestor is placed where

wires

enter

a

structure,

preventing

damage

to

electronic instruments within and ensuring the safety of individuals near them. Smaller versions of lightning arresters, also called surge protectors, are devices that are connected between

each

electrical

conductor

communications systems and the Earth. 32

in

power

and

These prevent the flow of the normal power or signal currents to ground, but provide a path over which high-voltage lightning current flows, by passing the connected equipment. Their purpose is to limit the rise in voltage when a communications or power line is struck by lightning or is near to a lightning strike. If 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-produced

extreme

voltage

spikes

in

incoming power lines can damage electrical home appliances.

33

POWER-LINE COMMUNICATION Power-line communication (PLC) carries data on a conductor that is also used simultaneously for AC electric power transmission or electric power distribution to consumers. It is also known as power-line carrier, power-line digital subscriber line (PDSL), mains communication,

fig.15 Power-line communication

Basics Power-line communications systems operate by adding a modulated carrier signal to the wiring system. Different types of power-line communications use different frequency bands. Since the power distribution system was originally intended for transmission of AC power at typical frequencies of 50 or 60 Hz, power wire circuits have only a limited ability to carry higher frequencies. The propagation problem is a limiting factor for each type of power-line communications. 34

ELECTRICAL ISOLATOR Circuit breaker always trip the circuit but open contacts of breaker cannot be visible physically from outside of the breaker and that is why it is recommended not to touch any electrical circuit just by 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.

Fig.16 Electrical isolator

So definition of isolator can be rewritten as Isolator is a manually operated mechanical switch which separates a part of the electrical power system normally at off load condition.

35

Types of Electrical Isolators 1) Double Break Isolator 2) Single Break Isolator 3) Pantograph type Isolator. Operation of Electrical Isolator As no arc quenching technique is provided in isolator it must be operated when there is no chance current flowing through the circuit. No live circuit should be closed or open by isolator operation. A complete live closed circuit must not be opened by isolator

36

ELECTRICAL INSULATOR Electrical Insulator must be used in electrical system to prevent unwanted flow of current to the earth from its supporting points. The insulator plays a vital role in electrical system. Electrical Insulator is a very high resistive path through which practically no current can flow. In transmission and

distribution

system,

the

overhead

conductors

are

generally supported by supporting towers or poles. The towers and poles both are properly grounded. So there must be insulator between tower or pole body and current carrying conductors to prevent the flow of current from conductor to earth through the grounded supporting towers or poles. Insulating Material

The main cause of failure of overhead line insulator, is flash over, occurs in between line and earth during abnormal over voltage in the system. During this flash over, the huge heat produced by arcing, causes puncher in insulator body. Viewing this phenomenon the materials used for electrical insulator, has to posses some specific properties. 37

Properties of Insulating Material The materials generally used for insulating purpose is called insulating material. For successful utilization, this material should have some specific properties as listed below1. It must be mechanically strong enough to carry tension and weight of conductors. 2. It must have very high dielectric strength to withstand the voltage stresses in High

Voltage system.

3. It must possesses high Insulation Resistance to prevent leakage current to the earth. 4. The insulating material Must be free from unwanted impurities. 5. There must not be any entrance on the surface of electrical insulator so that the moisture or gases can enter in it. 6. There physical as well as electrical properties must be less effected by changing temperature.

38

BATTERY ROOM A battery room is a room in a facility used to house batteries for backup or uninterruptible power systems. Battery rooms are found in telecommunication central offices, and to provide standby

power

to

computing

equipment

in

datacenters.

Batteries provide direct current (DC) electricity, which may be used directly by some types of equipment, or which may be converted to alternating current (AC) by uninterruptible power supply (UPS) equipment. The batteries may provide power for minutes, hours or days depending on the electrical system design, although most commonly the batteries power the UPS during brief electric utility outages lasting only seconds.

Fig.17 Battery Room

Battery rooms were used to segregate the fumes and corrosive chemicals of wet cell batteries (often lead–acid) from the operating equipment; a separate room also allowed better control of temperature and ventilation for the batteries.

39

OVER CURRENT RELAY

The primer winding is connected to C.T. of the line to protected

ammeter.

The

tapping

are

connected

to

the

adjustable setting by which the no. of relay coil turn can be varied. The flux produced

by the primary and secondary

winding are separated in phase and space and a rotational torque is step up. This rotational torque is controlled by special spring and brake magnet

Fig.20 OVER CURRENT RELAY

The disc spindle carries a moving contacts which brides two fixed contact when the disc has rotated through an angel, which can be adjustable to any value between 0-360*. The relay can give any desired time setting by the adjustment ofan angle. As thew torque increase with current,

therefore the

relay has an inverse the characteristics. When fault occur, the current through the primery exceed to pre set value the driving torque. Consequently ,the disc rotate through pre set angle 40

EARTH FAULT REALY

The upper electromagnet of the directional element carries a winding connected through a P.T to the system voltage called a voltage coil of the relay. The lower magnet of the same element carries another winding known as current coil of the relay. This winding energized through the C.T the fault current. The contacts of the directional element are connected in series with another winding over the lower magnet of the nondirectional current.

Fig 21 Earth Fault Relay

Under normal operating conditions, power flows in the normal direction in the circuit to be protected by the relay.

41

when the fault due to the short circuit or earth fault takes place the fault current flows through the current coil of the relay an a flux in the lower magnet of the directional element is produced while the current flux in this upper magnet of the direction element. The two fluxes produced a torque tending to close its contacts. The relay current also flows through the winding over the upper magnet of the non directional element which produced a flux in this magnet, this is cause emf is induced in the winding over the lower magnet of the non directional element. Because, this winding provides a closed path, the induced emf circulate a current which produced another flux these two fluxes, therefore produce a torque on the disc of non direction element to a closed contact in the trip circuit.

42

TOOLS USE IN ELECTRICAL

1. Fish Tape

Fig. 22.1 Fish Tape

A fish tape is used to pull stranded or solid wire through metal or PVC conduit. Cable lube is available to assist you in pulling the wires hrough the pipe. 2. Tape Measure

Fig.22.2 Tape Measure

A tape measure is use to measure heights for switches and outlets. You will also need it to center lighting fixture boxes. 3 Hammer

Fig. 22.3 Hammer

A hammer is used to secure boxes equipped with nail-on brackets to studs in a home. You’ll also need it to drive Romex straps when adding new Romex wiring in a home. 43

4. Voltmeter

Fig.22.4 Voltmeter

A voltmeter is used to check voltages and verify that circuits are indeed “live” 5. Ammeter

Fig.22.5 Ammeter

An ammeter is a measuring instrument used to measure the electric current in a circuit. Electric currents are measured in amperes (A), hence the name. Instruments used to measure smaller currents, in the milli ampere or microampere range, are designated as milli ammeters or micro ammeters. 6. Channel Lock Pliers

Fig.22.6 Channel Lock Pliers

Channel lock pliers are used to take knockouts out of the boxes, tighten down Romex connectors in the boxes, and adjust expansion-type ceiling-fan boxes. 44

7. Wire Strippers

Fig.22.7 Wire Strippers

Wire strippers are used to cut the insulation off of the wire. They are equipped with different sized cutting teeth for various sized wires. They also have a cutoff portion in order to cut the wire. 8. Side Cutter Diagonal Pliers

Fig.22.8 Side Cutter Diagonal Pliers

These cutting pliers, sometimes called side snips, are used to cut wire. They are specially designed with a cutting edge that goes down to the tip of the pliers. The advantage being that you can get into tight areas to trim wires. There are some that are equipped with live wire detection capabilities 9. Wire Crimpers

Fig. 22.9 Wire Crimpers

This tool strips the wire and also crimps lugs onto the wire 45

10. Screw driver

Fig. 22.10 Screw driver

A Phillips screwdriver has four blades used to install Phillipshead screws. The tip looks like a plus sign.

11. Tester pin

Fig. 22.11 Tester pin

A tester pin glows when electric current is present. This tool is used to check electric current in wall outlets. It is preferable to purchase a neon circuit tester in the range of 120 to 240 volts, so that you will be able to use it with most outlet voltages. However, you can purchase a neon circuit tester with a higher or lower voltage capacity if necessary each into a panel without proper lighting.

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12.Jumper Wire

Fig.22.12 Jumper Wire

A jumper wire is used to test for open electrical circuits. Electricians sometimes make their own jumper wire or they can be purchased at electricity stores. A jumper wire can help you better understand the circuitry and so avoid the chance of an electrical shock. It is most important never to use a jumper wire on a live appliance. 13.Flashlight

Fig.22.13 Flashligt

A light comes in handy in those places where lighting is limited.

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