MODULE 6: ELECTRICAL INSTALLATIONS COMPONENTS OF LT SWITCHGEAR: SWITCH FUSE UNIT (SFU), MCB, ELCB, MCCB, TYPES OF WIRES AND CABLES, EARTHING.

BEE
Unit – 6
Electrical Installations
6.1 Components Of Lt Switchgear: Switch Fuse Unit (Sfu), Mcb, Elcb, Mccb,
Types Of Wires And Cables, Earthling
Electrical protection equipment
Prerequisite:
1) Electromagnetism
2) Shock and its effects
3) Effect of temperature on a current carrying conductor or
4) Thermocouple
Learning outcomes at the end of this experiment student will be able to
1) Elaborate need of protect ion equipment in electrical systems
2) Explain the structure and operation of fuse, MCB, MCCB and ELVB.
3) Choose a protective device for its different electrical system with justification
Theory
Electrical power system operates at various voltage level from a 230 volt single
phase, 415 volt to 765 kilovolt three phase or even more. Electrical apparatus used
may be enclosed (e.g. motors) or please in open (e.g. transmission lines). all such
equipment undergoes abnormalities in their lifetime due to various reasons. It is
necessary to avoid these abnormal operating regions for the safety of the
equipment.
Even more important is the safety of the human person which may be endangered
due to exposure to live parts under fault or abnormal operating conditions. A small

current of the order of 50 mA is sufficient to be fatal. Whenever human security is
sacrificed for there exist the possibility of equipment damage, it is necessary to
isolate and de energized the equipment. designing electrical equipment from a
safety perspective is also a crucial design issue which will not protect it and provide
human safety under abnormal operating conditions. This job is assigned to electrical
protection systems. It encompasses apparatus protection and system protection.
This is generally carried out by using Switchgear is a generic term which includes all
the switching devices associated with power system protection. It also includes or
devices associated with control, metering and regulating of electrical power
systems. Assembly of such devices in a logical manner forms switchgear. In other
words system used for switching, controlling and protecting the electrical power
circuits and different types of electrical equipment and known as which gear. The
switchgear has to perform the function of carrying, making and breaking the normal
load current like a switch and it has to perform the function of clearing the fort in in
the power system. In addition to that, it also has the provision of metering and
regulating the various parameters of electrical power systems. Thus the
transformers, protection relays, measuring instruments, electrical switches,
electrical fuses, miniature circuit breaker, lightning arresters or surge arresters,
electrical isolators and other associated pieces of equipment.
Following are the major protective equipment used in household electrical
appliances:
1) Fuse
2) Miniature circuit breaker (MCB)
3) Earth Leakage Circuit Breaker (ELCB)
4) Moulded Case Circuit Breaker (MCCB)
Fuse
A) Types of fuses and applications
In the field of electronics or electrical, a fuse is an essential device used in various
electrical circuits which gives the protection from the overcurrent. It it comprises a
strip or a metal wire that dissolves when the heavy flow of current comprises a strip
or a metal wire that dissolves when the heavy flow of current supplies through it.
Once this device has function in an open circuit, it ought to ji wire or changed based
on the type of fuse. A fuse is an automatic disconnection of supply which is
frequently shortened to ADS. The alternative of the fuse is a stabilizer or circuit
breaker, but they have many different characteristics.
B) Why do we require Fuse?

These are used to prevent the home appliances from the high current or overload
damage. If we use a fuse in the homes, the electrical faults cannot happen in the
wiring and it doesn't damage the appliances from the fire of wire burning. When the
fuse gets break or damage, then an abrupt sparkle happens which made direct to
damage your home appliances. That is the reason we required different types of
fuses to guard our home appliances against damage.
C) Working principle of Fuse
The working principle of the fuse is “
heating consequence of the current”. It is
fabricated with a lean strip for thread of metallic
wire. The connection of the fuse in an electrical
circuit is always in series. When the too much
current is produced due to the heavy flow of
current in the electrical circuit the fuse get soft and
it opens the circuit. The extreme flow of current
main direct to the collapse of the wires and prevents the supply. Diffuse can be
changed by the new fuse with an appropriate rating. It can be designed with
elements like copper, zinc, aluminium and silver. They also perform like a circuit
breaker for breaking the circuit while the abrupt fault happens in the circuit. This
works like a safety measure for protector for humans from risk. Like this, the fuse
works
Fuse rating =
The selection of a fuse can be done by calculating the fuse rating by using the above
formula
 Write down the voltage (volts) and power (watts) of the appliance.
 Calculate the fuse rating.
 After the result use the maximum fuse rating. For instance, if the calculated fuse
rating is the maximum fuse rating. For example, if the calculated fuse rating is 7.689
amps, you can use an 8 amp fuse.
Different types of Fuses:
The fuses are classified into to several types based on the application namely AC
type fuse and DC type fuse. Again these fuses are classified into several types. The
following diagram illustrates the electrical fuse types chart based on the AC fuse and
DC fuse.

DC
fuse:
DC
fuses
are
available superior in size and DC supply has a stable value over 0 volts. So it is tough
to remove and deactivate the circuit. There will be a chance of generation of
electrical Arc between dissolved wires. To conquer this electrodes located at
battery distances. For this reason the size of the DC fuse gets amplified.
AC fuses:
The AC fuse is lighter in size and oscillated 50 to 60 times
in each and every second from least to highest. As a
result, there is no scope for Arc generation between the
dissolved wires. For this reason, they can be crammed
into a small size. Further, AC fuses are classified into two
parts namely HV fuses and LV fuses. Here LV and HV
indicates the low voltage and high voltage LV fuses. The
low voltage fuses are divided into five types such as rewirable, cartridge, dropout,
striker and switch fuses.
Rewirable fuses:
Rewirable fuses are LV fuses, which are almost used in
small applications like wiring in in the house, small scale
industries, and other tiny current applications. these
types of fuses include two essential parts such as a fuse
base which has two terminals like in and out. In general,
this element is fabricated with porcelain. Another part of

this fuse is a fuse carrier, which grip the fuse element. This element is fabricated
with aluminium, tinned copper and lead. The main advantage of a fuse carrier is, we
can simply plug and remove from the base of the fuse without the risk of shock. As
the fuse is damaged due to heavy current, then we can simply eliminate the fuse
carrier as well as put back the fuse wire.
Cartridge type fuses:
The cartridge type of fuses has entirely closed containers
and the metal contact as well. The applications of this
fuses mainly include low voltage (LV), high voltage (HV)
and small fuses. again this types of fuses are classified
into two types, they are D type and link type fuses.
D type Cartridge Fuse
This type of fuse is composed
with the cartridge, base of the
fuse, adapt or ring, and cap.
The base of the fuse includes a fuse cap, which is
packed with the fuse ingredient by cartridge using
an adapter ring. It is composed of the cartridge,
fuse base, cap and adaptor ring. The fuse base has the
fuse cap, which is fitted with the fuse element with a
cartridge through the adaptor ring. The connection
of the circuit is finished when the tilt of the cartridge
builts contact through the conductor.
High Rupturing capacity or Link Type Fuse:
The link type fuse is also known as high rupturing
capacity (HRC) or BS type fuse. In this sort of fuse, the
current flow with fuse element is specified under
standard condition in this BS type fuse, the flow of current
by fuse element is given under normal condition. The arc
which is generated by the fuse blown is controlled is
fabricated with porcelain, ceramic and silver. the
container of the fuse element is packed with silica sand.
This type of use is again characterized into two parts
includes a blade type and bolted type.
Blade and bolted type fuses

The knife type fuse for plugin type of
fuses are designed with plastic. this type
of use can be simply changeable in the electric current
exclusive of any load in bolted type fuse, plates of this
fuse are conducting are set to the base of the fuse.
Striker type fuse
Describe the type of fuse is
employed for tripping and closing the electrical
circuit. This fuses are having plenty of force as well
as displacement.
Switch type fuse
Basically the switch type
fuse is enclosed with
a metal switch and also a
fuse. These fuses are
mainly used in low and intermediate voltage levels.
HV (High voltage) Fuses
Generally, HV fuses are used
to protect the transformers
like instrument transformers,
small Power transformer and also used in power
systems. These fuses are normally charged for voltages
over 1500 volt to 138000 volte.
The fuse part in HV fuses are fabricated with either
copper, silver or in some cases tin is used, in order to
offer consistent and steady performance. These fuses are
classified into three types which include the following.
Cartridge type HRC fuse
The fuse component of the HRC is cut in The helix form
which evades the effect of the corona at the upper
voltages. It includes to fuse elements namely low
resistance and high resistance, and that are located
parallel by each other. The low resistance wires take the

usual current which is is blown out as well as decreases the short circuit current
throughout the fault state.
Liquid type HRC fuse
This type of fuse is packed with carbon tetrachloride also
preserved at both the tops of the caps. Once the error
occurs when the following current surpasses away from
the allowable limit and the element of the fuse is blown
out. the flute of the fuse performs as an Arc extinguishing
standard for the HRC fuse types. they may be used to
protect the transformer as well as the support protection
to the breaker circuit.
Expulsion type HV fuse
These types of fuses are extensively used to protect the
feeders as well as transformer due to they're low priced.
It is designed for 11kV, also their cracking capability is
up to 250 MVA. This type of use includes and unfilled
open finished cylinder designed with synthetic resin
bonded paper. The elements of the fuse are positioned in
the cylinder, and the tops of the tubes are linked to
appropriate equipment at every finish. The ark
generating is blown off in the inside covering of the
cylinder, and gases thus shaved destroys the arc.
A)Applications of Fuse
The different types of fuses and their uses have discussed are essential components
in all the electrical circuits. some of the main applications of uses in the electrical
and electronics field include the following.
Power Transformers, electrical appliances, like ACs (Air Conditioners), TV, washing
machines, music systems and many more, electrical cabling in home, mobile
phones, motor starters, laptops, power chargers, cameras, scanners, printers, add
photo copiers, automobiles, electronic devices and gaming's.
B)Advantages of an Electrical Fuse
1) It is the cheapest form of protection and it doesn't need any maintenance.

2) Its operation is completely automatic and requires less time as compared to
circuit breakers.
3) The smaller sizes of fuse element impose a current limiting effect under short
circuit conditions.
4) Its inverse time current characteristic enables its use for overload protection.
D)Disadvantages of an Electrical Fuse
1) Considerable time is required in replacing a fuse after the operation.
2) The current time characteristic of fuse cannot always be correlated with that of the
protective device.
Miniature Circuit Breaker:
Miniature Circuit breakers (MCB) are electromechanical devices which are used to
protect electrical equipment from an over current. MCB is a a mechanical switching
device which is capable of making, caring and breaking currents under normal
circuit conditions and also making, caring for a specified time and automatically
breaking currents under specified abnormal circuit conditions such as those of short
circuit. In short MCB is a device for over load and short circuit protection.
A) Construction :- The construction of
miniature circuit breakers is very simple,
robust and maintenance free. MCB is
replaced by a new one when it is failing
because MCB is not repaired or
maintained. There are three types of
miniature circuit breakers in construction,
1) Frame:- Frame is a rigid, strong,
insulated housing in which the other
components are mounted. It is a molded
case.
2) Trip unit : For the proper working of the miniature circuit breaker trip unit is
responsible. Two main types of trip mechanism are provided in Miniature circuit
breaker (MCB). a bimetallic strip provides protection against overload current and
an electromagnet provides protection against short circuit current. Trip unit is the
main part of the MCB.
3) Operating Mechanism :- The operating mechanism of MCB provides with the
manual operation for closing and opening operation of the miniature circuit breaker.
It has three positions “ON”, “OFF”, “TRIPPED”. By observing the position of the

switching latch one can determine the condition of MCB whether it is closed, tripped
or manually switched off. If the MCB is tripped due to overcurrent or overheating.
The external switching latch in the “TRIPPED” position. When manually switch off the
miniature circuit breaker, the switching latch will be in “OFF” position. The switch is
positioned at “ON”, in a closed condition of the miniature circuit breaker.
B)Working:- The principle of operation is simple. Functions of miniature circuit
breaker is interrupting the continuity of electrical flow through the circuit once a
fault is detected. In simple terms of MCB is a switch, which automatically turns
off when the overcurrent flowing through it. Generally, MCB is designed to to
protect against overcurrent and over temperature false. There are two contacts one
is fixed and the other movable. When the current exceeds the predefined limit a
solenoid forces the movable contact to open (ie. Disconnect from the fixed contact)
and the MCB getting off thereby stopping the current to flow in the circuit point the
MCB is manually turned on to restart the flow of current. This mechanism is used to
protect from the faults arising due to over current. To protect against fault arising
due to overheating for increase in temperature bimetallic strip is used. MCB are
generally designed to trip within 2.5 million seconds when an overcurrent fault
arises. In case of temperature rise or overheating it may take 2 seconds to 2 minutes
for the MCB to trip. If the circuit is overloaded for a long time, the bimetallic strip
becomes overheated and deformed. This the formation of bimetallic strip causes,
displacement of latch point moving contact of the MCB is show arrange by means of
spring pressure, with this large., That is little displacement of large causes, release
of spring and makes the moving contact to move for opening the MCB. The current
coil for trip coil is placed such a manner that during short circuit fault the MMF of that
causes its plunger to hit the same latch. And make the large to be displaced. Hence
the MCB will open in the same manner. And it protects the circuit from the
overcurrent overloading.
A) Advantages:-
1) With a miniature circuit breaker, it is very simple to resume to the supply. You just
need to push the knob of MCB back to on position. But in case of fuse, the entire fuse
wire needs to be replaced.
2) A miniature circuit breaker is more sensitive to current then fuse. It detects any
abnormality in the current flow and automatically switches off the electrical current.
3) A miniature circuit breaker is reusable and hence has less maintenance and
replacement cost point where as a fuse leads to the replaced whenever it goes
faulty.
4) In case of a miniature circuit breaker, the faulty zone of an electrical circuit can be
easily identified.
B) Types of MCB

There are three standard characteristics are available for domestic as well as
commercial MCB are given by B,C and D. Each type has its own function
Type B
MCB are mainly used where switching surges are small or
non exist and are generally suitable for domestic
applications and light commercial applications. There are no
devices with long high starting current in domestic
applications and has the best suited MCB is type B. these are
designed to trip at fault currents in the range of 3 to 5 times
the rated current. Suppose if the rated current is 10 ampere
then the MCB trips at 30-50 A.
Type C
MCB are designed for high
inductive circuits where surge
currents are expected. These are
generally used for commercial and
industrial applications where a
number of fluorescent lamps been
turned ON or starting of small
motors may give high search
currents.
These are more sensitive than type B MCB and causes reduced nuisance trips. Type
C MCB are designed to operate for
trip at the fault currents of 5 to 10
times that of rated current.
For 10 A type C MCB, the
operating current range is 50
– 100 A.
Type D
MCBs are designed for heavy
industrial applications where
normal surge currents are very
high. These are ideal for electrical welders and site
Transformers where frequent high surge currents
are expected.

The most common applications of type D MCBs include motors, UPS systems comma
x-ray machines, Transformers and battery charging systems. These are designed to
trip at 10 – 20 times The rated current. For 10 A type D MCBs, the operating current
range is 100 – 200 A.
The setting or characteristics of an MCP are fixed in the factory itself by the
manufacturer and they are not adjustable at the user end or at the site. Tripping
currents for operation at 0.1 second or less different MCBs are given below.
Type B 3-5 times rated current
Type C 5-10 times rated
current
Type D 10-20 times rated
current
Earth Leakage Circuit Breaker (ELCB)
An ECLB is one kind of safety device used for installing an electric device with high
Earth impedance to avoid shock. These device is identify small stray voltages of the
the electrical device on the metal enclosures and intrude the circuit if a dangerous
voltage is identified. The main purpose of Earth leakage circuit breaker is to stop
damage to humans and animals due to electric shock. Earth leakage circuit breaker
is a device used to directly detect currents leakage to earth from an installation and
cut the power and mainly used in TT earthing systems.
There are two types of ELCBs :
1) Voltage Earth leakage Circuit Breaker (voltage ELCB)
2) Current Earth Leakage Circuit System (Current ELCB)
Voltage ELCB have first introduced about 60 years ago and current ELCB was first
introduced about 40 years ago. For many years, the voltage operated ELCB and the
differential current operated ELCB were both are referred to as ELCB because it was
a simpler name to remember. But the use of a common name for two different
devices gave rise to.
Considerable confusion in the electrical industry. If the wrong type was used on an
installation, the level of protection given could be substantially less than that
intended. To ignore this confusion, IEC decided to apply the term residual current
devices (RCD) two differential current operated ELCBs. Residual current refers to
any current over and above the load current.
A) Working Principle of Voltage ELCB:-

ELCB is a
voltage
operated
device. It
has a coil
and if the
voltage
across the
coil
exceeds as
a
predetermined value such as 50 V, the current through the coil will be sufficient
enough to trip the circuit. Voltage ELCB is connected in between the metallic part of
equipment and the Earth. If we take an example of insulation failure then the voltage
across the coil of voltage ELCB will drive enough Karan to cut the power supply till
the manually reset. The way to identify an ELCB is by looking for green or green and
yellow Earth wire entering the device. They relay on voltage returning to the trip via
the earth wire during a fault and effort only limited protection to the installation and
no personal protection at all. You should use plugin 30 mA RCD's for any appliances
and extension leads that may be used outside as a minimum.
Advantages of voltage operated ELCB
 ELCB are less sensitive to fault conditions and have few nuisance trips.
 While current and voltage on the ground line generally fault current from live
wire, this is not continuously the case, therefore there are conditions in which an
ELCB can annoyance trip.
 When installation of the electrical instrument has two contacts to earth, a near
high current lighting attack will root a voltage gradient in the earth, offering the
ELCB sense coil with sufficient voltage to source it to a trip.
 If either of the soil wires became detached from the ELCB , it will no longer install
will frequently no longer be corrected earthed.
 These ELCB are the necessity for a second connection and the opportunity that
any extra connection to ground on the theatre system can in activate the detector.

Disadvantages of voltage operated ELCB
 They do not sense errors that don't permit current through the CPC to the ground
rod.
 They do not permit an only building systems to be simply divided into many
sections with independent error protection because earthing systems are typically
used mutual earth rod.
 They may be skipped outside voltages from something associated with the
earthing system like as metal, a TN-C-S or a TN-S Earth mutual neutral and earth.
 As electrical leaky utilizations like washing machines, some water heaters and
cookers might source the ELCB to trip.
 ELCB present an extra resistance and an extra point of failure in the earthing
system.
B)Working Principle of Current (ELCB) :
The working
of current
ELCB is quite
interesting but
easy. Current
operated
ELCB is also
known as
Residual
Current
devices
(RCD).
Residual
current device
(RCD) has a
toroidal iron
core over
which phase and neutral windings are wound. A search coil is also mood on the
same iron core which in turn is connected to the trip coil. Figure below shows the
constructional detail of RCD or current ELCB.
Under normal operating condition, the current through the phase building and
neutral building are same but both the windings are wound in such a manner to
oppose the mmfs of each other, therefore net mmf in the toroidal iron corewill be
zero. Let us consider a condition where Earth leakage current exists in the lord side.
In this case the current through the phase and neutral will no longer be equal rather
phase current will be more than the neutral current. Does MMF produced by face
building will be more than the MMF produced by neutral building because of which
a net MMF will exist in the toroidal iron core.

Net MMF in core = MMF by phase winding - MMF by neutral winding
This net MMF in the core will link with the search coil and aa MMF is changing in
nature (current is AC),an EMF will be induced across the terminals of search coil.
This will intern drive a current through the trip coil which will pull (because of
current flow through the trip coil ok, it will behave as an electromagnet and hence
will pull the lever to open contact) the supply contacts to isolate the power supply.
Notice that current ELCB works on residual current that is the reason it is also called
residual current device. A RCD/ Current ELCB is also provided with test button to
check the healthiness of the safety device. If you carefully observe the figure, you
will notice that, when we press the test button, load and face building are bypassed
due to which only MMF because of neutral winding will exist in the core (as there is
no opposing MMF as was the case with both the windings in service) which will
cause RCD to trip to isolate supply.
Moulded Case Circuit Breaker:
Molded Case Circuit Breaker are
electromechanical devices which
protect a circuit from overcurrent and
short circuit. They provide overcurrent
and short circuit protection for circuits
ranging from 63 Amps up to 3000 Amps.
Their primary functions are to provide a
means to manually open a circuit and
automatically open a circuit under
overload or short circuit conditions. The
overcurrent, in an electrical circuit result
from short circuit overload for faulty
design.
Unlike fuse, and MCCB can be easily reset after of faulty and offers improved
operational safety and convenience without incurring operating cost.
Moulded case circuit breakers generally have a thermal element for overcurrent
and magnetic element for short current release which has to operate faster. MCCBs
are manufactured such that end user will not have access to internal workings of the
overcurrent protection device. Generally constructed of two pieces of heavy duty
electrically insulated plastic, these two halves are riveted together to form the whole
point inside the plastic shell in a series of thermal elements and a spring loaded
trigger point when the thermal element gets too warm from an over current situation,
the spring strips, which in turn will shut off the electrical circuit.
A)Sizing the MCCBs : MCCBs in an electrical circuit should be sized according
to the circuit's expected operating current and possible fault currents. The
three main criteria while selecting MCCBs are:

 The rated working voltage (Ue) the MCCB should be similar to the system
voltage.
 The trip value of the MCCB should be adjusted according to the current drawn by
the load.
 The breaking capacity of the MCCB must be higher than the theoretical possible
fault currents.
A) Types of MCCB:
Type
s of
MCC
B
Operati
ng
current
Operati
ng time
Application Suitability Surge
current
Installation
location
Type
B
Trips
between
3 and 5
times
rated
current
(In)
0.04 – 13
seconds
Domestic
applications
(lighting
and
resistive
elements)
Resistive
load
application
Low Sub feeder of
distribution
board
Type
C
Trips
between
5 and 10
times
rated
current
(In)
0.04 – 5
seconds
Commercial
or industrial
applications
Inductive
load
applications
Modera
te
At
incoming/outgo
ing of
distribution
board
Type
D
Trips
between
10 to 20
times
rated
current
(In)
0.04 – 3
seconds
Commercial
or industrial
applications
Inductive
capacitive
load
applications
(pumps,
motor, large
winding mot
ors e.t.c.)
High At incoming of
distribution
board/panels
Type
K
Trips
between
8 to 12
times
rated
current
(In)
0.04 – 5
seconds
Industrial
applications
Inductive
and motor
loads with
high in rush
currents
High At incoming of
distribution
board/panels
Type
Z
Trips
between
2 to 3
0.04 – 5
seconds
Highly
sensitive to
short circuit
Medical
instruments
Very
low
At sub feeder of
of distribution
board for IT

times
rated
current
(In)
and are
used for
protection
of highly
sensitive
devices
such as
semiconduc
tor or
devices
equipment
6.2 Types Of Batteries, important characteristics, power consumption and
power factor
Cell: A device which is used as a source of EMF and which works on the principle of
conversion of chemical energy into electrical energy is called cell.
Battery: the combination of various cells to obtain desired voltage level is called as
a battery.
Electrolyte: which undergoes decomposition due to flow of electrons.
 Basic electrical energy generation in cell.
 In any cell two different conducting materials are immersed in an electrolyte. The
chemical reaction results in separating charges. The charges accumulate on the
conductor such charged conductors are called as electrodes.
+Ve charge electrodes-> anode
-ve charged electrodes-> cathode
 Discharge accumulated on electrodes create potential difference between two
conductors.
 The conductors and are marked as positive and negative and connected to load.
Thus chemical energy is converted into electrical energy. Hence cell is an
electrochemical device.
Types of cell
 Primary cell
 Secondary cell
Primary Secondary
Electrical energy
indirectly
Electrical
energy is

obtained from
chemical energy.
already
present in the
cell in form of
chemical
energy and
then converted
to electrical
energy.
Chemical
reactions are
irreversible
(cannot be
recharged)
Chemical
reactions are
reversible.
Cell is replaced
when it goes
down.
Cell is
recharged
back.
Polarisation is
present.
Polarization is
absent.
Low efficiency. High
efficiency.
Capacity is low. Capacity is
high
Less cost High initial
cost.
No maintenance
is required.
Frequent
charging and
other
maintenance is
required.
 basic components of battery
Positive electrode i.e. anode

Negative electrode i.e. cathode

Electrolyte

Separator

Lead acid battery
Construction

Positive

plate
or anode:- it
is lead
peroxide
plate of
chocolate
dark brown
colour.
Negative

plate or
cathode:- it is
made up of
pure lead
which is grey
colour.
Electrolyte:- for necessary chemical reaction solution of sulphuric acid is used as

electrolyte.
Separators:- the positive and negative plates are arranged in groups and are

placed alternately. the separators are used to prevent them from coming in
contact with each other resulting in short circuit of cell.
Plate connector:- the number of negative and positive plates are assembled

alternately. To connect the positive plates together separate connectors are used
which are called plate connectors. The upward connection of the plate connectors
are nothing but the terminals of the cell.
Vent plug:- these are made up of rubber and screwed to the cover of cell. It

functions to allow the escape of gases and prevent escape of electrolyte.
Charging and discharging of lead acid battery
 When the current is passed for the first time through electrolyte the
In the electrolyte is electrolysed as:
 Hydrogen ion is positively charged get attracted towards one electrodes which
acts as cathode the hydrogen does not react with lead electrode hence retains its
original state and colour.
 The oxygen ion as negatively charged get attracted towards other lead plate
which acts as anode oxygen combines with lead and form lead peroxide this results
in dark brown in colour.

 hence there exist a potential difference between anode and cathode which is
used to drive external circuit.
Discharging:-
When external supply is disconnected and a resistance is connected across the
anode and cathode then current flows through the resistance drawing and electrical
energy from the battery this is discharging.
Recharging:
- the cell
provides the
discharge
current for
limited time and
it is necessary to
recharge it after
regular time
interval. Again and EMF is injected through cell terminal with help of external
supply.
Rating of lead
acid battery
The capacity

is about
hundred to 300
Ampere hours.
The voltage

is 2.2 volt for
fully charged
condition.

The cost is low.

The internal resistance is very low.

The current rating are high.

The ampere hour efficiency is about 90 to 95% with 10 hour rate.

Maintenance and precautions to be taken for lead acid battery
The battery must be recharge immediately when it discharges.

The level of electrolyte must be kept above top of plates.

The rate of charge and discharge should not exceed as specified by

manufacturer.
Maintain specific gravity of electrolyte between 1.28 to 1.18.

the loss of water due to evaporation and gasing must be made up using only

distilled water.
The connecting plugs should be kept clean and properly tightened.

It should not be discharged till its voltage for below 1.8 volt.

It should not be kept long in discharged condition.

The temperature of battery should not exceed 45°c otherwise plates get

deteriorate rapidly.
The battery terminal should not be shorted to check whether battery is charged

or not.
Applications
In emergency lighting systems.

In automobiles for starting.

UPS systems

Railway signalling

Electrical substations and power stations

For component feeder drop in case of heavy loads.

For energizing trip coils in release and switchgears.

Lithium ion battery
The lithium ion battery works on the principle of movement of lithium ions from
electrodes.
Construction
The lithium ion battery is made up of an anode cathode, separator, electrolyte and to
current collectors (+ve and -ve)

Anode-> lithium ion uses carbon electrode as its anode with a current collector of
thin copper foil.
Cathode -> it uses lithium cobalt oxide commonly used for cathode with the current
collector made up of thin aluminium foil.
Separator-> a separator is a fine porous polymer film.
Electrolyte-> it is the solution based on a lithium salt in an organic solvent.
Both electrodes are made up of materials which can “intercalote” or “absorb” the
lithium ions.
Working
 Lithium ions are inserted in cathode.
 For charging the battery is connected to an external power supply.
 Due to this oxidation occurs at the cathode and it loses electrons which are
negatively charged.

 to maintain the charge balance in the cathode equal number of lithium ions are
already dissolved in electrolyte solution.
 The lithium ion travel through electrolyte and reach to anode.
 The separator use does not allow the electrons to flow through an electrolyte. The
electrons travel through the external wire and reach to anode from cathode.
 At cathode the electrons get tied with lithium ions.
 At time of discharging the opposite reactions occur
 Anode releases electrons and ions.
 Ions get dissolved in electrolyte and electrons travel from cathode to anode
through external circuit.
 Due to flow of electrons from the external circuit the current is established and
device connected to battery is operated.
 When the cathode is full of lithium ions discharging stops and battery needs to be
recharged again.
Advantages
Cell voltage is high when is about 3.6 volte. less number of cells are required if

high voltage is required.
The battery is light in weight and compact in size.

It holds charge for longer period. It only losses 5% of its charge month

It is not required to discharge it completely before charging.

It has built-in protection to prevent overheating.

It is rechargeable battery.


Disadvantages
Its performance is affected due to high temperature.

Not possible to recharge if it is completely discharged.

It is costly

It can burst into flames if separator get damaged.

It requires protection circuit to maintain voltage and current within safe limits.

Applications
Used in cameras
 and calculators.
Used in mobile phones radios and laptops

Used in aerospace applications.

Used in electric vehicles and mine detectors.

Used in toys and rechargeable flashlights.

Battery efficiency
 it is defined as ratio of output during discharging to the input required during
charging.
Ampere hour efficiency or quantity
 it is defined as ratio of output in ampere Hours during discharging to input in
ampere Hours during charging.
It is denoted by
2.Watt hour efficiency
It is defined as the ratio of output in watt hour during discharging to the input in watt
hours during charging denoted by

Concept of depth of discharging
 The depth of discharge is Q. Key factor for any factory it is denoted by DOD.
 It indicated the degree to which the battery can be discharged to certain
minimum voltage from its full state of charge.
 The the depth of discharge give the indication that up to which level of discharge
the battery capacity can be used safely.
 DOD is defined as the capacity in ampere hours that is discharged from a fully
charged battery, divided by battery nominal capacity.
 DOD is normally represented in percentage.
 For example if a 200 Ah battery is charged at 90 A for 30 minutes then its depth of
discharged is
=22.5%
 The department of discharge is important because the lifespan of many battery
such as lead acid battery and lithium ion battery depends heavily upon the number
of charge and discharge cycles.
 If the DOD is high then lifespan of battery get shortened .for example battery may
have 5000 cycles at 20% but only 1500 cycles at 80% of the body as shown in below
graph

Grouping of
batteries
A single battery is
not sufficient to
provide the
necessary voltage in
many cases. Thus
number of batteries
are connected in
following manner to
obtain desired
voltage and result.
Series grouping of

batteries
Parallel grouping

of batteries
Series parallel

grouping of
batteries
Series grouping

E= EMF of each batteries
r= Internal resistance of each battery
V=Total voltage =n×E volts
=Total resistance
= Total batteries
=
In series circuit current remain same so in this method does not improve current
capacity. The current capacity is same as that of each battery connected in series.
But voltage can be increased by increasing number of batteries n.
Parallel grouping
 In this method positive terminal of batteries are connected together and negative
terminals are connected together as shown above.
 The Terminal of each battery must be same as E
V=battery voltage=E=EMF
r=internal resistance of each battery

=Current through nth branch.
I=Total current
 In parallel grouping the voltage remains the same but by increasing number of
batteries the current capacity can be increased.
Series parallel grouping
 each group is a series combination of batteries as shown in above figure and
various groups are connected in parallel.
 This is used to satisfy both voltage and current requirement of load.
Safety precautions in battery maintenance
Person doing the maintenance must be authorized person.

Must have protecting equipment such as goggles, chemical resistance gloves,

agron and shoes.
Before entering battery room ensure that the ventilation system is operable and

in service.
Verify that the UPS is off and power code is disconnected from source.

Ensure that sufficient water facilities are available nearby.


Never connect cell in series of parallel. They do not have identical output

voltage
Verify circuit polarities before making the connections.

Use protective devices while charging or discharging.

Use temperature census while charging or discharging.


MODULE 6: ELECTRICAL INSTALLATIONS COMPONENTS OF LT SWITCHGEAR: SWITCH FUSE UNIT (SFU), MCB, ELCB, MCCB, TYPES OF WIRES AND CABLES, EARTHING.

More Related Content

What's hot (20)

Similar to MODULE 6: ELECTRICAL INSTALLATIONS COMPONENTS OF LT SWITCHGEAR: SWITCH FUSE UNIT (SFU), MCB, ELCB, MCCB, TYPES OF WIRES AND CABLES, EARTHING. (20)

More from Sitamarhi Institute of Technology (20)

Recently uploaded (20)

MODULE 6: ELECTRICAL INSTALLATIONS COMPONENTS OF LT SWITCHGEAR: SWITCH FUSE UNIT (SFU), MCB, ELCB, MCCB, TYPES OF WIRES AND CABLES, EARTHING.