b.e. third year class electrical 2014 term: 16/2 (dec-16...
TRANSCRIPT
1
COURSE PLANNER SUBJECT: HIGH VOLTAGE ENGINEERING-
[2160904]
B.E. – Third Year
Class–Electrical 2014
Term: 16/2 (DEC-16 to APR-17)
Faculty: Prof. V.B. RATHOD Prof. M.K. TAMBOLI Prof. S.P. SHAH Prof. C.P.VAIDYA Prof. J.P. PATEL
Contents: 1. Course Outcomes 2. Course Contents[Syllabus] 3. List of Reference Books 4. List of Experiments
5. Major Equipments required for Experiments 6. List of Open source software and learning websites required for
experiments 7. Active Learning Assignments and Tutorial.
Instructions for Assignment/Tutorial:
[1] This set of Assignment-Tutorial consist the collection of questions of past GTU Question
papers.
[2] Attend those questions which are bold marked and/or frequently asked in GTU exam.
[3] Students should make a separate Chapter wise Files[write on File Pages] to solve these
Questions.
[4] Students must solve these given set of Assignments by themselves only.
[5] Assessment of given assignment should be done regularly after completion of each
chapter by Students from the respective faculty members.
2
[1] Course Outcomes:
After learning the course the students should be able to
1. Understand the basic generation and measurement of High voltage and
High current for testing purposes.
2. Comprehend Breakdown phenomenon in air, solid and liquid insulation.
3. Test high voltage electrical Equipment with various testing devices.
4. Basic of electrostatic fields and field stress control.
5. Basic concepts and technics of generation of high voltage.
6. Measurement technics of high voltage.
7. Understand testing procedures of insulating material and insulation
coordination.
8. Understand testing and analyze different insulating material for electrical
equipment.
3
[2] Course Contents:
CHAPTER
NO. SYLLABUS
Total
Hrs
%
Weightage
1
Electrostatic fields and field stress control : Electrical field distribution and breakdown strength of insulating materials- fields in homogeneous, isotropic materials - fields in multi-dielectric, isotropic materials - numerical method: Finite Element Method (FEM), charge simulation method (CSM)
04 08
2
Electrical breakdown in gases Gases as insulating media - ionization and decay processes, Townsend first ionization coefficient, photoionization, ionization by interaction of metastable with atoms, thermal ionization, deionization by recombination, deionization by attachment–negative ion formation, examples - cathode processes – secondary effects, photoelectric emission, electron emission by positive ion and excited atom impact, thermionic emission, field emission, Townsend second ionization coefficient, secondary electron emission by photon impact,examples - transition from non-self-sustained discharges to breakdown,the Townsend mechanism, examples - the streamer or ‘kanal’ mechanismof spark, examples - the sparking voltage–Paschen’s law, penning effect,the breakdown field strength, breakdown in non-uniform fields- partial breakdown, corona discharges
05 12
3
Breakdown in liquid and solid dielectrics: Liquid as insulators, breakdown in liquids - electronic breakdown, suspended solid particle mechanism, cavity breakdown, electro-convection and electro hydrodynamic model of dielectric breakdown, examples –staticelectrification in power transformers, transformer oil filtration, transformer oil test, alternative liquid insulations like vegetable oils, esters and silicon oils - breakdown in solids, intrinsic breakdown, streamer breakdown, electromechanical breakdown, edge breakdown and treeing, thermalbreakdown, erosion breakdown, tracking - breakdown of solid dielectricsin practice, partial discharges in solid insulation, solid dielectrics used inpractice.
07 16
4
Generation of high voltages : Generation of high direct voltages, half and full wave rectifier circuits, voltage multiplier circuits, Van de Graff generators, electrostatic generators, examples - generation of alternating voltages, testing transformers, cascaded transformers, resonant transformers, examples - impulse voltages, impulse voltage generator circuits, Marx circuit, operation, design and
07 16
4
construction of impulse generators, examples - impulse current generator - control systems
5
Measurement of high voltages : High direct voltage measurement, peak voltage measurements by sparkgaps,sphere gaps, reference measuring systems, uniform field gaps, rod gaps, factors affecting sphere gap measurements, examples – electrostaticvoltmeters - ammeter in series with high ohmic resistors and high ohmic resistor voltage dividers - generating voltmeters and field sensors – the measurement of peak voltages, the Chubb–Fortescue method, highvoltage capacitors for measuring circuits - voltage dividing systems and impulse voltage measurements, generalized voltage generation andmeasuringcircuit, voltage dividers, interaction between voltage dividerand its lead, the divider’s low-voltage arm - digital recorders, errorsinherent in digital recorders
06 16
6
Overvoltages, testing procedures and insulation coordination The lightning mechanism, energy in lightning, nature of danger –simulatedlightning surges for testing - switching surge test voltage characteristics laboratory high-voltage testing procedures and statistical treatment ofresults, examples - insulation coordination, insulation level, statisticalapproach to insulation coordination, correlation between insulation andprotection levels - modern power systems protection devices, moa –metal oxide arresters
04 10
7
Non-destructive insulation test techniques : Measurement of d.c. resistivity - dielectric loss and capacitance measurements, the Schering bridge, current comparator bridges, loss measurement on complete equipment, null detectors - partial-discharge (PD) measurements, the basic PD test circuit, PD currents, PD measuringsystemswithin the PD test circuit, measuring systems for apparent charge, sources and reduction of disturbances, other PD quantities, calibration of PD detectors in a complete test circuit, digital PD instruments
05 12
8
High voltage testing: Testing of insulators and bushings - testing of isolators and circuit breakers - testing of cables - testing of transformers - testing of surge diverters – radio interference measurements - design, planning and layout of high voltage laboratory
04 10
5
[3] List of Reference Books : 1. Kuffel, E., Zaengl W.S., Kuffel J., “High Voltage Engineering
:Fundamentals”Butterworth- Heinmann (A division of Reed Educatonal& Profession Publishing Limited), 2nd Edition, 2000.
2. Naidu M. S. and Kamaraju V., “High Voltage Engineering”, fourth Edition, TataMcGraw- HillPublishing Company Limited, New Delhi, , 2009.
3. Wadhwa C.L., "High Voltage Engineering", third edition, New Age publishers, New Delhi, 2010.
4. Rakosh Das Begamudre, “High Voltage Engineering, Problems and Solutions”, New Age International Publishers, New Delhi, 2010.
5. Dieter Kind, Kurt Feser, “ High Voltage Test Techniques”, Reed educational andprofessional publishing ltd. (Indian edition), New Dehli-2001
6. M. Khalifa, "High Voltage Engineering-Theory and Practice", Marcel Dekker, Inc. New York and Basel,1990.
7. Hugh M. Ryan, “High Voltage Engineering and Testing”, 2nd edition, The Institution of Electrical Engineers, London, United Kingdom, 2001
6
[4] List of Experiments :
SR.
NO. LIST OF EXPERIMENT
1 STUDY OF HIGH VOLTAGE LABORATORY.
2 SIMULATION OF HIGH D.C. VOLTAGES GENERATION USING VOLTAGE
DOUBLER CIRCUIT AND CASCADED VOLATGE DOUBLER CIRCUITS.
3 SIMULATION OF HIGH A.C. VOLATGES GENERATION USING CASCADE
TRANSFORMER UNIT WITH ISOLATION TRANSFORMERS.
4 TO DETERMINE THE DIELECTRIC STRENGTH OF TRANSFORMER OIL.
5 DETERMINATION OF BREAKDOWN VOLTAGE FOR DIFFERENT TYPES OF
INSULATING MATERIALS.
6 TO STUDY ABOUT HORN GAP APPARATUS FOR CORONA FORMATION.
7 TO STUDY ABOUT ROD GAP IS AN ABSOLUTE METHOD OF MEASUREMENT OF
THE PEAK VALUE OF HIGH VOLTAGE.
8 TO STUDY ABOUT SPHERE GAP APPARATUS FOR THE MEASUREMENT OF
HIGH VOLTAGE.
9 TO STUDY ABOUT IMPULSE GENERATOR.
10 TO STUDY ABOUT PARTIAL DISCHARGE DETECTION.
7
[5] Major Equipments required for Experiments :
1 OIL TEST SET FOR INSULATING OIL 0.60KV MAKE:HIGHVOLTAGE INDIA
2 DIE ELECTRIC STRENGHT MEASUREMENT KIT 30KV AC/40 KV DC,MAKE:HIGH VOLTAGE INDIA
3 HORNGAP APPRATUS MAKE: HIGH VOLTAGE INDIA
4 TRANSFORMER FOR HIGH VOLAGE TESTING 100 KV/50MA,[2 OF 50KV CASCADE CONNECTION] MAKE: HIGH VOLTAGE INDIA
5 ROADGAP APPRATUS & SPHERE GAP ASSEMBLY COMBINED ,MAKE: HIGH VOLTAGE INDIA
8
[6]List of Open source software and learning websites required for experiments : OPEN SOURCE SOFTWARE: 1. Finite Element Method Magnetics FEMM 2. LTSpice for circuit simulation, 3. KiCAD for CAD application WEB-BASED TOOLS FOR DESIGN: 1. http://www.fairchildsemi.com/support/design-tools/power-supply-webdesigner/ 2. http://www.ti.com/lsds/ti/analog/webench/overview.page CIRCUIT LAB: 1. https://www.circuitlab.com/editor/ OPEN SOURCE MATH TOOLS: 1. http://maxima.sourceforge.net/ 2. http://www.sagemath.org/ 3. http://www.scilab.org/ 4. http://www.gnu.org/software/octave/ ONLINE EXPERIMENT PORTAL: 1. http://vlab-ee1.iitkgp.ernet.in LEARNING WEBSITE: 1. http://www.electrical-engineering-portal.com/ 2. http://nptel.iitm.ac.in/courses.php
9
[7] Learning Assignments / Tutorial : Chapter-1 Electrostatic fields and field stress control :
Electrical field distribution and breakdown strength of insulating materials - fields in homogeneous, isotropic materials - fields in multi-dielectric, isotropic materials - numerical method: charge simulation method (CSM)
SR
NO. QUESTION YEAR MARKS
1 Discuss briefly the “Charge Simulation Method” for solving field problems and estimation of potential distribution.
OCT-16 07
2 Define: Breakdown strength, Solid-gas or solid-liquid insulation.
3 What is Finite Element Method? Brief it for solving the field problems
OCT-16 07
10
Chapter-2
Electrical breakdown in gases Gases as insulating media - ionization and decay processes, Townsend first ionization coefficient, photoionization, ionization by interaction of metastable with atoms, thermal ionization, deionization by recombination, deionization by attachment–negative ion formation, examples - cathode processes – secondary effects, photoelectric emission, electron emission by positive ion and excited atom impact, thermionic emission, field emission, Townsend second ionization coefficient, secondary electron emission by photon impact, examples - transition from non-self-sustained discharges to breakdown,the Townsend mechanism, examples - the streamer or ‘kanal’ mechanismof spark, examples - the sparking voltage–Paschen’s law, penning effect,the breakdown field strength, breakdown in non-uniform fields- partial breakdown, corona discharges
ATTEMPT ANY FOUR:
SR
NO. QUESTION YEAR MARKS
1 Explain corona Discharges. Explain corona discharge. Discuss concept of positive corona and negative corona.
NOV-11 JAN-13 DEC-13 MAY-13 MAY-15 DEC-15
07
2
Explain breakdown in Electronegative Gases. NOV-11 MAY-12
07 What are electronegative gases? Discuss the criteria for its breakdown. Why its breakdown strength is higher than other gas?
3
State and explain Paschen’s law. How do you account for the minimum voltage for breakdown under a given pd condition?
MAY-11 NOV-11 MAY-12 MAY-13 DEC-13 DEC-15 OCT-16
07
What is Paschen’s law? Explain significance of existence of minimum sparking potential in paschen’s curve. Explain Paschen’s law with appropriate graphical diagram. Describe the current growth phenomenon in a gas subjected to uniform electric fields. What is Paschen’slaw ?
4 Define vacuum and its categories. Describe breakdown in vacuum.
NOV-11 JAN-13 MAY-12 MAY-16
07
5 Describe various factors influencing breakdown in gas. MAY-12 07
6 Define Townsend’s first & second ionization co-efficient. ExplainTownsend’s discharge. Obtain current growth equation due to first and second
MAY-12 JAN-13 DEC-13
07
11
ionization. MAY-15 MAY-16
8 Explain streamer theory of breakdown in gases. MAY-13 DEC-14
07
9
In a certain Townsend type discharge, the following measurements were made. d (mm) 4 6 8 10 12 14 16 18 20 22 I (pA) 25 35 45 60 80 120 180 300 550 2000 Deriving any equations used, determine the Townsend’s first and second ionization coefficients.
MAY-14 07
10
Derive an expression for the corona inception in a two conductor system with radius of each conductor r and the spacing between the conductors, d. Also describe the process of stable corona formation by discussing the relationship of the corona radius and electric stress at the corona boundary
MAY-14 07
11
If a Steady State current of a certain gas is 5.4 ×10-8 A at 8 kV at a distance of 0.4 cm between the plane electrodes. Keeping the Field constant and reducing the distance to 0.1 cm results in a current of 5.5 ×10-9 A. Calculate Townsend’s primary ionization coefficient α. Also find value of y at 0.9 cm.
OCT-16 07
12
Chapter-3
Breakdown in liquid and solid dielectrics: Liquid as insulators, breakdown in liquids - electronic breakdown, suspended solid particle mechanism, cavity breakdown, electro-convection and electro hydrodynamic model of dielectric breakdown, examples – static electrification in power transformers, transformer oil filtration, transformer oil test, alternative liquid insulations like vegetable oils, esters and silicon oils - breakdown in solids, intrinsic breakdown, streamer breakdown, electromechanical breakdown, edge breakdown and treeing, thermal breakdown, erosion breakdown, tracking - breakdown of solid dielectrics in practice, partial discharges in solid insulation, solid dielectrics used in practice
ATTEMPT ANY FIVE:
SR
NO. QUESTION YEAR MARKS
1 Explain the various theories that explain breakdown in commercial liquid dielectrics.
MAY-11 DEC-14 MAY-16
07
2 Explain thermal breakdown in solid dielectrics. How this mechanism is more significant than the other mechanisms Explain Thermal breakdown in solid dielectric.
MAY-11 MAY-13
07
3
What are “Treeing” and “Tracking”? Explain clearly the two processes in solid dielectrics.
MAY-11
NOV-11
MAY-12
JAN-13
DEC-14
DEC-15
MAY-16
OCT-16
07
Explain solid breakdown due to Treeing & Tracking.
Explain “Treeing” and “Tracking” clearly the two processes
in solid dielectrics.
Explain the phenomenon ‘Treeing and Tracking’ in solid insulating materials under electrical stress. How does it lead to breakdown?
4 Discuss Epoxy Resins & Polyesters as solid Dielectrics. NOV-11 07
5 Explain various theories for breakdown in commercial liquids.
MAY-12 07
6
Explain intrinsic strength of solid dielectric and explain differentmechanism by which breakdown in solid dielectric occurs. Explain intrinsic breakdown mechanism of solid dielectric material.
MAY-12
MAY-15 07
7
Explain Purification & Breakdown tests for Liquid Dielectric.
NOV-11 JAN-13 May-13 DEC-15 OCT-16
07 What are the different methods and means for purification of liquid dielectrics? Explain breakdown and filteration tests for liquid dielectric.
13
8 Explain cavitation & bubble theory and stressed oil volume theory of liquid dielectric.
MAY-13
MAY-15 07
9
List out physical and chemical properties of mineral oil. What are the alternative liquid dielectrics used worldwide as replacement of mineral oil? Give their merits and demerits.
DEC-13 07
10 Explain various theories of breakdown in solids in brief. DEC-13 07
11 Explain liquid insulation purification system with neat diagram
DEC-13 07
12
A certain dielectric can be considered to be represented by the equivalent circuit shown in figure. What is the maximum voltage that can be applied across the dielectric if partial discharges in air are to be avoided. State any assumptions made
MAY-14 07
13 Describe briefly 4 processes by which solid insulation may breakdown below their intrinsic strength.
MAY-14 07
14
A solid dielectric material of dielectric strength of 6.0 has
an internal void of thickness 1 mm. The specimen is 1 cm
thick and is subjected to rms voltage of 10 kV. If the void is
filled with air (breakdown strength of air = 3 kV/mm), give
remark on occurrence of internal discharge.
MAY-15 07
15 What is ‘Stressed Oil Volume Theory’? How does it
explain breakdown in large volumes of commercial liquid
dielectrics? OCT-16 07
14
Chapter-4
Generation of high voltages : Generation of high direct voltages, half and full wave rectifier circuits, voltage multiplier circuits, Van de Graff generators, electrostatic generators, examples - generation of alternating voltages, testing transformers, cascaded transformers, resonant transformers, examples - impulse voltages, impulse voltage generator circuits, Marx circuit, operation, design and construction of impulse generators, examples - impulse current generator - control systems
ATTEMPT ANY SIX:
SR
NO. QUESTION YEAR MARKS
1
Describe, with a neat sketch the working of a Van de Graff generator. What are the factors that limit the maximum voltage obtained ?
MAY-11
DEC-14
MAY-13
MAY-16
OCT-16
07
Write short notes on Van de Graaff Generator.
2
A 12-stage impulse generator has 0.126 μF capacitors. The wave front and the wave tail resistances connected are 800 ohms and 5000 ohms respectively. If the load capacitor is 1000 pF, find the front and tail times of the impulse wave produced.
MAY-11
DEC-14
OCT-16
07
3 Explain the different schemes for cascade connection of transformers for producing very high a.c. voltages.
MAY-11 07
4
What is the principle of operation of a resonant transformer ? How is it advantageous over the cascade connected transformers ?
MAY-11
DEC-13
DEC-14
MAY-15
MAY-16
07 Explain resonant transformers for high voltage AC generation. Discuss the advantages and limitations of it.
5
Describe the construction, principle of operation and application of a multistage Marx’s surge generator. Draw & explain Marx circuit and modified Marx circuit of multistage impulse generator. Discuss differences between these two.
MAY-11 NOV-11 JAN-13 MAY-13 DEC-14 DEC-15 MAY-16
07 07
6 Why is controlled triggering required in an impulse generator ? Explain typical trigger arrangement.
NOV-11 07
7 Explain how are switching impulse generated in Laboratory. NOV-11 DEC-15
07
8
An impulse generator has 8 stages with each condenser rated for 0.16 μF and 125 KV. The load capacitor available is 1000 pF. Find the series resistance and damping resistance needed to produce 1.2/50 μs impulse wave. What is the Maximum
NOV-11 07
15
output voltage of the generator, if the charging voltage is 120 KV ?
9 Explain cascade connection for producing a. c. high voltage. Explain the use of isolating transformer.
MAY-12
May-15
MAY-16
07
10 With help of neat diagram, explain operation and working of Van de graph generator.
MAY-12 MAY-15
07
11 Explain Tesla coil for producing high frequency high voltages with its derivation of output voltage.
JAN-13 DEC-15
07
12
An impulse generator has eight stages with each condenser rated for 0.16μF and 125KV.The load capacitor available is 1000pF.Find the series resistance and the damping resistance needed to produced 1.2/50 μs impulse wave. What is the maximum output voltage of the generator, if the charging voltage is 120 KV?
JAN-13 07
13
A 10 stage cockraft-Walton circuit has all capacitors of 0.06 μF. The secondary voltage of the supply transformer is 100KV at a frequency of 150 Hz. If the load current is 1 mA, Determine (1) voltage regulation (2) The ripple (3) The optimum number of stages for maximum output voltage. (4) The Maximum output voltage.
MAY-13
MAY-16 07
14 State and explain the difference between testing transformer and power transformer.
DEC-13 07
15
Explain Cockcroft Walton circuit for HVDC generation. DEC-13 DEC-15 OCT-16
07 Explain the working of Cockcroft-Walton circuit with
schematic diagram.
Explain Voltage Multiplier Circuit for generation of High
Voltage.
16
A 200 kVA, 230V/50 kV, 50 Hz, testing transformer has an 8% leakage reactance and a 2% winding resistance. An insulator of capacitance 20 nF is to be tested at 300 kV using this transformer as part of the resonance circuit. Determine the value of the inductance (Q-factor = 15) required to obtain resonance. Determine also the value of the input voltage required
MAY-14 07
17
A six-stage impulse generator designed to generate the standard waveform (1.2/50 μs) has a per stage capacitance of 0.06 μF to be used to test transformers with anquivalent winding to earth capacitance of 1 nF. A peak output voltage of 550 kV is required for testing the transformer. The wave front time is to be defined based on 30% and 90% values. (a) With the aid of appropriate calculations select the values of the resistive elements in the circuit to produce the required waveform. State any assumptions made.
MAY-14 07
16
18
A ten stage Cockraft-Walton circuit has all capacitors of 0.06 F. The secondary voltage of the supply transformer is 100 kV at a frequency of 150 Hz. If the load current is 1 mA, determine (i) voltage regulation (ii) the ripple (iii) the optimum number of stages for maximum output voltage (iv) the maximum output voltage
MAY-14
MAY-16 07
17
Chapter-5
Measurement of high voltages : High direct voltage measurement, peak voltage measurements by spark gaps, sphere gaps, reference measuring systems, uniform field gaps, rod gaps, factors affecting sphere gap measurements, examples – electrostatic voltmeters - ammeter in series with high ohmic resistors and high ohmic resistor voltage dividers - generating voltmeters and field sensors – the measurement of peak voltages, the Chubb–Fortescue method, highvoltage capacitors for measuring circuits - voltage dividing systems and impulse voltage measurements, generalized voltage generation and measuring circuit, voltage dividers, interaction between voltage divider and its lead, the divider’s low-voltage arm - digital recorders, errors inherent in digital recorders
ATTEMPT ANY SIX :
SR
NO. QUESTION YEAR MARKS
1
Explain how a sphere gap can be used to measure the peak value of voltages. What are the parameters and factors that influence such voltage measurement ? How a sphere-gap can be used to measure high voltage? Explain the factors affecting such measurements?
MAY-11
JAN-13
MAY-13
DEC-13
DEC-14
MAY-15
DEC-15
07
2
Explain with neat diagram the principle of operation of an electrostatic voltmeter. Discuss its advantages and limitations for high voltage measurements. Explain electrostatic voltmeter with neat diagram. Also state the governing equation for it. Show that the deflecting torque of an electrostatic voltmeter is proportional to the product of the square of the applied voltage and the rate of change of capacitance. Also draw a diagram of Abraham Voltmeter and describe its operation principle.
MAY-11
MAY-13
DEC-13
DEC-14
MAY-14
DEC-15
07
3 Discuss the different methods of measuring high d.c. voltages. What are the limitations in each method ?
MAY-11 OCT-16
07
4 What are the different types of resistive shunts used for impulse current measurements? Discuss their characteristics and limitations.
MAY-11 07
5 Which are different factors that affect the sparkover voltage of sphere gap ? Discuss it in brief.
NOV-11 07
6 Draw & Explain series capacitor peak voltmeter.
NOV-11 JAN-13 MAY-13 DEC-15 MAY-16
07
18
7 Discuss High Voltage Schering Bridge. MAY-13 DEC-15
07
8 Discuss measurement of Dielectric constant & Loss tangent of capacitor.
NOV-11 MAY-13 DEC-15
07
9 Give the basic circuits for measuring peak voltage for a.c. and impulse. Explain how they differ.
MAY-12 07
10
Show that the deflecting torque of an electrostatic voltmeter is proportional to the product of the square of the applied voltage and the rate of change of capacitance. Also draw a diagram of Abraham Voltmeter and describe its operation principle.
11 Explain principle, working , advantages & disadvantages of Generating voltmeters
JAN-13 DEC-15
07
12 Explain potential dividers for impulse voltage measurement by CRO. Suggest arrangement to minimize errors.
JAN-13 DEC-15
07
13 Explain partial measurement test for insulation quality assessment. What is the procedure to measure partial discharge?
MAY-13 DEC-13
07
14 Explain the set up for measurement of d.c. resistivity. DEC-13 07
15
Explain briefly, with the aid of suitable diagrams, why a potential divider connected at the output of an impulse generator needs to be matched to the cable connecting it to an oscilloscope and how matching may generally be achieved. You may select any specific type of potential divider as an example
MAY-14 07
16
Describe with the aid of suitable diagrams how the dielectric loss in a lossy capacitor is measured in comparison with a standard lossless capacitor using the x-y mode in the oscilloscope. Show that the area of the ellipse displayed is proportional to the loss.
MAY-14 07
17
A peak reading voltmeter is required to measure voltage up to 150 kV. The peak voltmeter uses an RC circuit, a micro ammeter and a capacitance potential divider. The potential divider has a ratio of 1200 : 1 and the micrometer can read up to 10 A. Determine the value of R and C if the time constant of RC circuit is 8 secs
MAY-14 07
18
Design a peak reading voltmeter along with a suitable micro-ammeter such that it will be able to read voltages, up to 100 kV (peak). The capacitance potential divider available is of the ration 1000 : 1.
OCT-16 07
19 Discuss the effect of (i) nearby earthed objects (ii) humidity and (iii) dust particles on the measurements using sphere gaps
MAY-14 07
20 Describe the principle of Generating Voltmeter operation. List out advantages and disadvantages of Generating
MAY-15 07
19
Voltmeter.
21 What are different methods of high DC voltage measurement? ExplainGenerating voltmeter method in detail.
MAY-16 07
22
The capacitive voltage divider is used in electrostatic voltmeter for measurement of high voltage ac. A three terminal standard compressed air capacitor of 1nF and mica capacitor of 1μF are available. If 100V ac voltmeter is connected across mica capacitor, what will the maximum available reading of voltmeter? Ignore capacitance of meter.
MAY-15 07
23
Explain capacitive voltage transformer with its schematic representation, equivalent circuit and phasor diagram.
MAY-16 OCT-16
07 What is Capacitance Voltage Transformer? Explain with phasor diagram how a tuned capacitance voltage transformer can be used for voltage measurements in power systems.
24 Explain the importance of RIV measurements for EHV power apparatus.
OCT-16 07
20
Chapter-6
Overvoltages, testing procedures and insulation coordination The lightning mechanism, energy in lightning, nature of danger – simulatedlightning surges for testing - switching surge test voltage characteristics laboratory high-voltage testing procedures and statistical treatment ofresults, examples - insulation coordination, insulation level, statisticalapproach to insulation coordination, correlation between insulation andprotection levels - modern power systems protection devices, moa –metal oxide arresters
ATTEMPT ANY THREE:
SR
NO. QUESTION YEAR MARKS
1 What is meant by insulation co-ordination ? How are the protective devices chosen for optimal insulation level in a power system ?
MAY-11
MAY-13
DEC-14
DEC-15
MAY-16
OCT-16
07
2 Discuss surge arresters as protective devices. JAN-13 07
3 Explain the lightning mechanism including leader and return stroke with appropriate diagram.
DEC-13
DEC-14 07
4 Write a comprehensive note on metal oxide arrestors DEC-13
DEC-14 07
5 Explain why a steep fronted surge waveform is more likely to cause damage to the line end turn insulation of a transformer winding rather than elsewhere,
MAY-14 07
6 Explain with neat sketches the mechanism of lightning discharge
MAY-14 MAY-16
07
7 Explain the mechanism of lightning strokes.
MAY-15 07
8 What is composite insulation? How does short term breakdown differ from long.
OCT-16 07
21
Chapter-7
Non-destructive insulation test techniques : Measurement of d.c. resistivity - dielectric loss and capacitance measurements, the Schering bridge, current comparator bridges, loss measurement on complete equipment, null detectors - partial-discharge (PD) measurements, the basic PD test circuit, PD currents, PD measuring systems within the PD test circuit, measuring systems for apparent charge, sources and reduction of disturbances, other PD quantities, calibration of PD detectors in a complete test circuit, digital PD instruments
ATTEMPT ANY THREE:
SR
NO. QUESTION YEAR MARKS
1
What are partial discharges and how are they detected under power frequency operating conditions ? Briefly explain how partial discharges in insulation can be detected and display.
MAY-11
JAN-13
MAY-15
MAY-16
07
2
Determine the specific heat generated in the test specimen due to dielectric loss if the dielectric constant and loss angle of the specimen are 3.8 and 0.0085 respectively. The electric field is 40 KV/cm at 50 Hz.
MAY-11 07
3 Discuss High voltage Schering Bridge
NOV-11
JAN-13
DEC-14
07
4 Explain the partial discharge tests for high voltage cables. How fault is located?
MAY-12 07
5
Figure shows a high Voltage Schering Bridge used in a particular measurement. The values of the components at balance are shown on the diagram. Determine the value of the unknown capacitor and its loss tangent. All necessary equations must be derived
MAY-14 07
6 Explain the high voltage schering bridge for tan δ and capacitance measurement of insulators.
MAY-15 07
7 Briefly explain the methods used for calibrating the partial discharge detectors.
OCT-16 07
22
Chapter-8
High voltage testing: Testing of insulators and bushings - testing of isolators and circuit breakers - testing of cables - testing of transformers - testing of surge diverters – radio interference measurements - design, planning and layout of high voltage laboratory
ATTEMPT ANY THREE:
SR
NO. QUESTION YEAR MARKS
1 Explain the different electrical tests done on isolators and circuit breakers.
MAY-11
DEC-14 07
2 Explain High voltage Test on Insulator. Explain the insulation testing of insulators.
NOV-11 DEC-14 MAY-15
07
3 Explain Impulse Testing of Power Transformer. Explain impulse testing of power transformer with a diagram of set up.
JAN-13
DEC-14 MAY-16
07
4 Explain classification of High voltage Laboratories. JAN-13 07
5 Explain various high voltage tests done on power transformers
DEC-13 07
6
Give design, planning and layout of high voltage laboratory. If possible give brief summary about major high voltage laboratories in India. Draw and discuss about the layout of high voltage laboratory.
DEC-13 MAY-14 DEC-14
07
7 Explain test facilities and testing equipments in high voltage
Laboratories
DEC-15
MAY-16 07