SIX WEEK INDUSTRIAL TRAINING REPORT
ON
66 KV SUBSTATION LATIALA
TRAINING ON PSPCL
SUBMITTED BY:MANDEEP SINGH
ELECTRICAL ENGG
UNI. ROLL NO:-1706622
SUBMITTED TO:ELECTRICAL ENGG
DEPARTMENT
GNDEC LUDHIANA
INDUSTRIAL TRAINING REPORT
ON
66 KV SUBSTATION
AT
PSPCL
NAME:BRANCH:UNI. ROLL NO:SESSION:TRAINING AT :TRAINING ON :DATE :-
MANDEEP SINGH
ELECTRICAL ENGINEERING
1706622
2017-2021
PSPCL
66 KV SUBSTATION LATIALA
FROM 03/06/2019 TO 18/07/19
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.
46
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.
47