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Module
1
Introduction
Version 2 EE IIT, Kharagpur

Lesson
1
Introducing the Course on
Basic Electrical
Version 2 EE IIT, Kharagpur

Contents
1 Introducing the course (Lesson-1)

4

Introduction ………………………………………………………………………
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4

Module-2 D
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circuits …………………………………………………………………
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C transient …………………………………………………………………
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C circuits ……………………………………………………
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8

Module-6 Magnetic circuits & Core losses ………………………………………
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9

Module-8 Three phase induction motor …………………………………………………
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C Machines …………………………………………………………
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12

Version 2 EE IIT, Kharagpur

Introduction
Welcome to this course on Basic Electrical Technology
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It is needless to mention that how much we are
dependent on electricity in our day to day life
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Apart from learning d
...
c circuit analysis both under steady state and transient
conditions, you will learn basic working principles and analysis of transformer, d
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Finally working principles of some popular and useful indicating measuring
instruments are presented
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The course is spread over 10 modules covering these 3parts, each module having two or more lessons under it as detailed below
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Modules 4, 5 and 8 by Prof
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K
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Modules 2, 3 and 10 by Prof
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D
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Modules 1, 6, 7 and 9 by Dr
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K
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1
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1
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It will give you a feel of a modern power system with names and function
of different major components which comprise it
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1-2
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At the end of each lesson a set of problem is provided to test
the readers understanding
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The contents of each
lesson are described below
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1 Introduction to electrical circuits
This lesson provides some basic concepts on Kirchoff’s law, difference between linear
and nonlinear circuits, and understanding the difference between current and voltage
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sources
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Each
topic of this lesson is clearly illustrated by solving some numerical problems
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2 Loop Analysis of resistive circuit in the context of dc voltages and
currents
In this lesson, loop analysis method based on Ohms law and Kirchoffs voltage law is
presented to obtain a solution of a resistive network
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Several
numerical problems including both voltage and current sources have been considered to
illustrate the steps involved in loop analysis method
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3 Node-voltage analysis of resistive circuit in the context of dc voltages and
currents
Node voltage analysis is the most general and powerful method based on Kirchhoff’s
current law is introduced in this lesson for the analysis of electric circuits
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The
procedure for analyzing a dc network is demonstrated by solving some resistive circuit
problems
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4 Wye (Y) – Delta (∆) or Delta (∆) – Wye (Y) transformations
The objective of this lesson is to introduce how to convert a three terminal Delta (∆) /
Wye (Y) network into an equivalent Wye (Y) / Delta (∆) through transformations
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Some typical problems are solved to familiarize with these
transformations
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5 Superposition Theorem in the context of dc voltage and current sources
acting in a resistive network
This lesson discusses a concept that is frequently called upon in the analysis of linear
circuits (See 2
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The principle of superposition is primarily a conceptual aid that can
be very useful tool in simplifying the solution of circuits containing multiple
independent voltage and current sources
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Concept
of superposition theorem is illustrated by solving few circuit problems
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6 Thevenin’s and Norton's theorems in the context of dc voltage and
current sources in a resistive network
In this lesson we consider a pair of equivalent circuits, called Thevenin’s and Norton’s
forms, containing both resistors and sources at the heart of circuit analysis
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Reduction of linear circuits to either equivalent form is explained through solution of
some circuit problems
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2
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) exhibits a nonlinear characteristic and it is
presented in this lesson
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This technique is also referred to as load line analysis method that is
intuitively appealing to analyze some complex circuits
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These techniques are discussed through worked out
problems
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1 and 3
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The
transients in a circuit containing energy storage elements occur when a switch is turned on or off
and the behavior of voltage or a current during the transition between two distinct steady state
conditions are discussed in next two lessons
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The contents of each lesson are
described below
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1 Study of DC transients in R-L and R-C circuits
This lesson is concerned to explore the solution of first order circuit that contains
resistances, only single energy storage element inductance or capacitance, dc voltage
and current sources, and switches
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In this lesson, the transient and steady state behavior in
a circuit are studied when a switch is turned on or off
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The solution of differential equation restricted to
second order dynamic systems for different types of forcing function are included in
Appendix of this, lesson
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3
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In
this lesson, the transient and steady state behavior of a second order circuit are studied
under three special cases namely, (i) over damped system (ii) critically damped system
(iii) under damped system that can arise depending upon the values of circuit
parameters
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Module-4 Single phase AC circuits
There are six lessons (4
...
6) in this module, where the various aspects related to ac circuits fed
from single phase supply, are described
...
1

Generation of single phase ac and fundamental aspects
The principle of generation of sinusoidal (ac) waveforms (single phase) in an ac
generator is first presented
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4
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Then, the phasor algebra relating the mathematical operations, involving two or more
phasors (as the case may be), from addition to division, is taken up, with examples in
each case, involving both the forms of phasor representations as stated
...
3

Steady state analysis of series circuits
The steady state analysis of series (R-L-C) circuits fed from single phase ac supply is
presented
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The use of phasor algebra is also taken up
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4
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The phasor diagram is drawn showing all currents,
and voltage drops
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4
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Firstly, the case of series (R-L-C) circuit is taken up, and the
condition of resonance, along with maximum current and minimum impedance in the
circuit, with the variation in supply frequency is determined
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This results in minimum current and maximum impedance here
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6

Concept of apparent, active and reactive power
The formula for active (average) power in a circuit fed from single phase ac supply, in
terms of input voltage and current, is derived in this lesson, followed by definition of the
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term, ‘power factor’ in this respect
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Module-5 Three phase AC circuits
There are only three lessons (5
...
3) in this module
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5
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The balanced
windings as described can be connected in star- and delta-configuration
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Also described is
the relation between phase and line currents, when the windings are connected in delta
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5
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The currents
in all three phases are determined, with phasor diagram drawn showing all voltages and
currents
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The power (active) consumed in the balanced load is derived in terms of
the line voltage and currents for both cases
...
3

Measurement of three-phase power
The total power (in all three phases) is measured using two wattmeters only
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The phasor diagram with balanced threephase load is drawn
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Module-6 Magnetic circuits & Core losses
In this module there are two Lessons 21 and 22 as enumerated below
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1 Simple magnetic circuits
It is often necessary to produce a desired magnetic flux, in a magnetic material (core)
having a definite geometric shape with or without air gap, with the help of current
passing through a coil wrapped around the core
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Both linear and non-linear
magnetic circuit problems are discussed through worked out problems
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2 Eddy current & hysteresis losses
These two losses are produced in any magnetic material which is subjected to an
alternating time varying fields
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C machines /equipments
working on electromagnetic principle these losses occur
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C machine armature too
these losses occur
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Finally methods adopted to minimize these losses discussed
as losses bring down the efficiency of any machines
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In this
module having 6 lessons, various aspects of a transformer are explained and discussed as per the
break up given below
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1 Ideal single phase transformer
Clear concept of ideal transformer goes a long way to understand the equivalent circuit
representation of a practical transformer discussed in the next lesson
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To have a rough and quick estimate of primary current for a given
secondary current of a practical transformer one need not consider detail equivalent
circuit but rather pretend that the transformer is ideal and apply simple relation of ideal
transformer
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7
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In this lesson, it has
been shown how these can be taken into account in the equivalent circuit
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Concept of approximate
equivalent circuit discussed and meaning of equivalent circuit referred to primary and
secondary side are explained
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3 Testing, efficiency and regulation of transformer
Two basic tests called open circuit and short circuit test are discussed and then it is
explained how equivalent circuit parameters of a single phase transformer can be
obtained from the test data
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Importance of efficiency and regulation are discussed and working formula for them
derived
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Regulation
is essentially a measure of change of magnitude of the secondary voltage from no load
to full load condition and its value should be low
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7
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Therefore, stepping up or down of 3-phase voltage is required
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Three separate identical
transformers can be connected appropriately to serve the purpose
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Another way of having a three phase transformer, is to construct it
as a single unit of three phase transformer
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Various important and popular connections of 3-phase transformer (such as star/star,
star/delta, delta/star etc
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The importance of dot convention while making
such connections are pointed out
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Vector grouping of various three phase transformer connection are generally not meant
for a first year course and can be avoided
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7
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Such transformers are called
auto-transformers
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Here, ideal auto transformer is assumed to show how to find
out current distribution in different parts of the winding when it is connected in a
circuit
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7
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Module-8 Three phase induction motor
In this module consisting of six lessons (8
...
6), the various aspects of the three-phase induction
motor are presented
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1

Concept of rotating magnetic field
Before taking up the three-phase induction motor (IM), the concept of rotating magnetic
field is introduced in this lesson
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It is shown that a constant magnitude of
magnetic field (flux) is produced in the air gap, which rotates at ‘synchronous speed’ as
defined in terms of No
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8
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The principle of torque
production in a three-phase IM is explained in detail, with the term, ‘slip’ defined here
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3

Per phase equivalent circuit and power flow diagram
The equivalent circuit of a three-phase IM is obtained, which is explained step by step
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8
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The
characteristics are drawn, with typical examples, such as variation in input (stator)
voltage, and also in rotor resistance (with external resistance inserted in each phase)
...
5

Types of starters
The need of starter in a three-phase IM to reduce the stating current drawn is first
explained
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Lastly, the rotor resistance starter for a wound rotor (slip ring) IM is briefly presented
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6

Single-phase induction motor and starting methods
It is first shown that starting torque is not produced in a single phase induction motor
(IM)
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Lastly, the shaded pole
single-phase IM is described
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1 Constructional features of DC machines
The lesson discusses the important construction features of DC machines
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The
functions of commutator segments and brushes, which convert the AC voltage to DC
form, are explained
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It has been
shown that the number of parallel paths in the armature will be different in the two types
of windings
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9
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C machines
The lesson begins with an example of single conductor linear D
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It
helps to develop the concept of driving force, opposing force, generated and back emf
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C generator and motor are explained
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9
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Irrespective of the fact that whether the machine is operating as a generator
or as a motor, the same two equations can be applied
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The topic of calculation of cross magnetizing and demagnetizing mmf’s can be avoided
depending upon the syllabus requirement and interest
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4 DC Generators
The lesson introduces the types of DC generators and their characteristics
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The open circuit
characteristic (O
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C) and the load characteristics of both kinds are discussed
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C
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9
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The operation of a three-point starter is
explained
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At the end, a brief account of various methods of electrical braking is
presented
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6 Losses, efficiency and testing of D
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Major losses in a DC machine are first enumerated, and
Swinburne’s test and Hopkinson’s tests are explained to estimate them
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7 Problem solving in DC machines
In this lesson, some typical problems of DC motors and generators are worked out
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Module-10 Measuring instruments
The magnitude of various electric signals can be measured with help of measuring instruments
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The study of DC and AC instruments for measuring voltage, current signals and
subsequently induction type energy meter, are described in this module consisting of three
lessons (10
...
3)
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1 10
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10
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PMMC
instruments are used as a dc ammeter or dc voltmeter where as MI instruments are
basically used for ac current or voltage measurements
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Subsequently, the advantages,
limitations and sources of errors of these instruments are studied therein
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In this
context some problems are solved to illustrate the meaning of multi-range meters
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2 Study of electrodynamics type instruments
Electrodynamics meters can measure both dc signals and ac signals up to a frequency of
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Torque expressions for such instruments (as an
ammeter, voltmeter and a wattmeter) are derived and then mode of meter connections to
the load as an ammeter, voltmeter and a wattmeter are presented
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A compensation technique is introduced to
eliminate the errors in wattmeter readings
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The sources of error and their corrections are
highlighted
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10
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Development of torque expression and errors in energy
meters are studied
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Finally, the extension of meter range using instrument transformers is
discussed

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