Industrial Power Engineering and Applications Handbook

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Contents
Prejkice
Ackiiowledgernents
Technical support
Introduction

Part I Selection, Testing, Controls and Protection of Electric Motors
1 Theory, Performance and Constructional Features of Induction Motors
lntroduction . Brief theory of the operation of a
polyphase motor. Motor output and torque . Motor
ratings and frame sizes . Preferred ratings at different
voltages . Influence of service conditions on motor
performance . No-load performance . Effect of steel of
laminations on core losses . Circle diagram . Types of
induction motors . Mounting of motors Enclosures *
Weatherproof motors (WP) . Degree of protection .
Cooling systems in large motors . Single phase
motors Theory of operation

2 Motor Torque, Load Torque and Selection of Motors
Motor speed-torque curve . NEMA rotor designs .
Special designs of rotors . Effect of starting current on
torque . Load torque or opposing torque 1 Selection of
motors . Time of start-up and its effect on motor
performance . Thermal withstand time

3 Duties of Induction Motors
Duty cycles Continuous duty (CMR) (SI) Periodic
duties . Factor of inertia (FI) Heating and cooling
characteristic curves ' Drawing the thermal curves .
Rating of short motors . Equivalent output of short
time duties . Shock loading and use of a flywheel

4 Starting of Squirrel Cage Induction Motors
Direct on-line starting (DOL) . Reduced voltage starting

5 Starting and Control of Slip-ring Induction Motors
Important features of a slip-ring motor . Starting of slipring
motors . Hypothetical procedure to calculate the
rotors resistance. Speed control of slip-ring motors '
Moving electrode electrolyte starters and controllers

6 Static Controls and Braking of Motors
Speed control in squirrel cage motors . Speed control
through solid-state technology . Vu control (speed
control at constant torque) . Phasor (vector) control .
Use of phasor control for flux braking . Control and
feedback devices . Application of solid-state
technology ' Conduction and commutation . Circuit
configurations of semiconductor devices . Smoothing
ripples in the d.c. link ' Providing a constant d.c.
voltage source 4 Providing a constant current source .
Generation of harmonics and switching surges in a
static device switching circuit . Protection of
semiconductor devices and motors . Energy
conservation through solid-state technology .
Application of static drives . Speed variation through
variable-speed fluid couplings . Static drive versus fluid
coupling . D.C. drives Braking . Induction generators
' Inching or jogging . Number of starts and stops

7 Special-Purpose Motors
Textile motors . Crane motors . Determining the size
of motor . Sugar centrifuge motors Motors for deepwell
pumps . Motors for agricultural application .
Surface-cooled motors 8 Torque motors or actuator
motors . Vibration and noise level . Service factors .
Motors for hazardous locations . Specification of
motors for Zone 0 locations . Specification of motors
for Zone 1 locations . Motors for Zone 2 locations .
Motors for mines, collieries and quarries . Intrinsically
safe circuits, type Ex. 'i' . Testing and certifying
authorities . Additional requirements for ciritical
installations Motors for thermal power station
auxiliaries . Selection of a special-purpose motor

8 Transmission of Load and Suitability of Bearings
Direct or rigid couplings . Flexible couplings .
Delayed-action couplings . Construction and principle
of operation . Belt drives . Checking the suitability of
bearings . Suitability of rotors for pulley drives

9 Winding Insulation and its Maintenance
Insulating materials and their properties . Ageing of
insulation . Practices of insulation systems . Procedure
for vacuum pressure impregnation . Maintenance of
insulation . Monitoring the quality of insulation of HT
formed coils during manufacturing

10 Installation and Maintenance of Electric Motors
Installation of bearings and pulleys . Important checks
at the time of commissioning Maintenance of electric
motors and their checks . Maintenance of bearings .
General problems in electric motors and their remedy .
Winding temperature measurement at site . Analysis of
insulation failures of an HT motor at a thermal power
station

11 Philosophy of Quality Systems and Testing
Philosophy of quality systems . Testing of electrical
machines . Procedure for testing . Load test . No-load
test . Tolerances in test results Certification of motors
used in hazardous locations

12 Protection of Electric Motors
Purpose . Unfavourable operating conditions . Fault
conditions . Protection . Single-device motor
protection relays . Summary of total motor protection .
Motor protection by thermistors . Monitoring of a
motor’s actual operating conditions . Switchgears for
motor protection . Selection of main components .
Fuse-free system of Electrical Machines

Part II Switchgear Assemblies and Captive Power Generation
13 Switchgear and Controlgear Assemblies
Application . Types of assemblies . Conventional
designs of switchgear assemblies (also referred to as
switchboards) . Design parameters and service
conditions for a switchgear assembly . Deciding the
ratings of current-carrying equipment, devices and
components . Designing a bus system . Designing a
switchgear assembly . HT switchgear assemblies .
General guidelines during installation and maintenance
of a switchgear or a controlgear assembly . Power
circuits and control scheme diagrams . Painting .
Procedure of switchgear and control gear assemblies
and treatment of effluent

14 Testing of a Metal-enclosed Switchgear
Philosophy of quality systems . Recommended tests .
Procedure for type tests . Procedure for routine
tests . Procedure for field tests An introduction to
earthquake engineering and testing methods

15 Instrument and Control Transformers:
Introduction . Types of Transformers . Common
features of a voltage and a current transformer .
General specifications and design considerations for
voltage transformers Precautions to be observed
while installing a voltage transformer . Current
transformers . Short-time rating and effect of
momentary peak or dynamic currents . Summary of
Specifications of a CT Precautions to be observed
when connecting a CT . Test Requirements

Assemblies
Application and Selection
16 Captive (Emergency) Power Generation
Introduction . DG set . Operating parameters . Theory
of operation . Guidelines on the selection of a DG set
. Types of loads . Starting of a DG set . Protection of
a DG set . Parallel operation . Procedure of parallel
operation . Recommended protection for a
synchronizing scheme . Load sharing by two or more
generators . Total automation through PLCs

Part III Voltage Surges, Overvoltages and Grounding Practices
17 Voltage Surges - Causes, Effects and
Introduction . Temporary overvoltages . Voltage surge
or a transient . Transient stability of overhead lines .
Causes of voltage surges . Definitions . Causes of
steep rising surges . Effect of steep-fronted TRVS on
the terminal equipment (motor as the basis)
. Determining the severity of a transient . Protection of
rotating machines from switching surges . Theory of
surge protection (insulation coordination)

18 Surge Arresters: Application and
Surge arresters . Electrical characteristics of a ZnO
surge arrester . Basic insulation level (BIL) .
Protective margins . Protective level of a surge arrester
. Selection of gapless surge arrester . Classification of
arresters . Surge protection of motors . Pressure relief
facility . Assessing the condition of an arrester

19 Circuit Interrupters
Circuit interrupters . Theory of circuit interruption
with different switching mediums (theory of
deionization) . Theory of arc plasma . Circuit breaking
under unfavourable operating conditions . Circuit
interruption in different mediums . Current chopping .
Virtual current chopping . Containing the severity of
switching surges . Comparison of interrupting devices

20 Temporary Overvoltages and System
Theory of overvoltages . Analysis of ungrounded and
grounded systems . The necessity of grounding an
electrical system . Analysis of a grounded system .
Arc suppression coil or ground fault neutralizer .
Ground fault factor (GFF) . Magnitude of temporary
overvoltages . Insulation coordination . Application of
different types of grounding methods (for HT, HV and
EHV systems) . Important parameters for selecting a
ground fault protection scheme

21 Grounding Theory and Ground Fault Remedies Selection Grounding Protection Schemes
Protection of a domestic or an industrial single phase
system . Ground fault on an LT system . Ground fault
protection in hazardous areas. . Ground leakage in an
HT system . Core-balanced current transformers
(CBCTs). Ground fault (GF) protection schemes
Contents vii

22 Grounding Practices
Grounding electrodes
Measuring the ground resistance Metal for the
grounding conductor Jointing of grounding
conductors . Maintenance of grounding stations
Grounding practices in a power generating station
Tolerahle potential difference at a location . Voltage
gradients . Determining the leakage current through a
body . Measuring the average resistivity of soil .
Improving the performance of soil . Determining the
ground fault current . Designing a grounding grid
Resistivity of soil (p) .

Part IV Power Capacitors
23 Power Capacitors: Behaviour, Switching
Phenomena and Improvement of Power Factor
Introduction . Application of power capacitors Effect
of low PF . Other benefits of an improved power
factor . Behaviour of a power capacitor in operation .
Generation of triple harmonics in an inductive circuit.
Generation of harmonics by a power electronic circuit.
Resonance . Effective magnitude of harmonic voltages
; ~ n dc urrents When harmonics will appear in a
\ystem Filter circuits : suppressing harmonics in a
power network . Excessive charging currents
(switching inrush or making currents) Limiting the
inrii\h currents . Capacitor panel design parameters .
Capacitor rating for an induction motor. Location of
capacitors Automatic PF correction of a system .
Switching sequences . PF correction relays

24 System Voltage Regulation
Capacitors for improvement of system regulation
Series capacitors Rating of series capacitors
Advantages of series compensation . Analysis of a
system for series compensation . Reactive power
management Influence of line length (ferranti effect)
To optimize the power transfer through reactive
control . Transient stability level Switching of large
reactive banks

25 Making Capacitor Units and Ratings of
Making a capacitor element . A critical review of
internally protected capacitor units . Self-healing
capacitors . Making a capacitor unit from elements .
Making capacitor banks from capacitor units Rating
Switching Devices
and selection of components for capacitor duty Fast
discharge devices

26 Protection, Maintenance and Testing of
Protection and safety requirements . Installation and
maintenance of capacitor units Test requirements

27 Power Reactors
Introduction Selection of power reactors . Magnetic
charecteristics . Design criterion and I . q5
characteristics of different types of reactor .
Application

Capacitor Units
Part V Bus Systems
28 Carrying Power through Metal-enclosed
Introduction . Types of metal-enclosed bus systems .
Design parameters and service conditions for a metal
enclosed bus system Short-circuit effects . Service
conditions Other design considerations ‘Skin effect .
Proximity effect . Sample calculation for designing a
2500 A non-isolated phase aluminium busbar system

29 Recommended Practices for Mounting Bus Systems Buses and Making Bus Joints
Precautions in mounting insulators and conductors .
Making a joint Bending of busbars
30 Properties and Ratings of Current-Carrying
Properties and current ratings for aluminium and
copper conductors . Current-carrying capacity of’
copper and aluminium conductors

31 An Isolated Phase Bus System
An isolated phase bus (IPB) system Constructional
features . Special features of an IPB system .
Enclosure heating . Natural cooling of enclosures
Continuous rating . Forced cooling . Influence of a
space field on the metallic structures . Fault level .
Voltage drop . Forming of sections for IPB systems
Determining the section and size of conductor and
enclosure Sample calculations

32 Testing a Metal-enclosed Bus System
Philosophy of quality systems . Recommended tests
Procedure for type tests Routine tests . Field tests
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