INSTITUTE OF AERONAUTICAL ENGINERING DUNDIGAL ELECTRICAL AND ELECTRONICS ENGINEERING Course code : 067(07-08) Course title : High voltage engineering Course structure Lectures Tutorials Practical credits 04 0 Course coordinator : Mr.T.Anil kumar, EEE Department UNIT - CO S Write the expression for electric field intensity. What is di-electric strength? Give any two parameters on which breakdown voltage of insulation depends. 4 Explain the process of ionization by collision in gas insulation. Give the units of breakdown voltage. REMEMBER 6 Give two importance of liquid insulations. REMEMBER 7 Write poisson s euqtion. REMEMBER 8 What are the two methods to determine potential distribution REMEMBER 9 Define field enhancement factor. REMEMBER 0 Give the names of numerical methods for electric field Computation REMEMBER How the surge voltages are originated? What is super node? ANALYZE, Write application of insulation materials in transformer 4 Write application of insulation materials in circuit breaker Write application of insulation materials in bushings. 6 Write application of insulation materials in cables. 7 Write application of insulation materials in power capacitor. 8 Write application of insulation materials in rotating machines. QUESTION BANK ON SHORT DISCRIPTIVE ANSWER QUESTION How is the electric field stress is controlled? What are the insulation materials used in high voltage transformer? Explain about electric field stress.
4 Explain the distribution and control of surge voltages in high voltage equipment. What are the insulation materials used in high voltage circuit breaker? 6 Explain the method of charge simulation. 7 What are the insulation materials used in high voltage rotating machines? 8 Explain the finite element analysis and step by step procedure. 9 Explain how boundary element method is different from charge simulation method 0 What are the insulation materials used in high voltage cables? Explain the necessity of transient and surge voltages in power equipment.. What are the insulation materials used in high voltage power capacitor? Explain the finite element metghod 4 What are the insulation materials used in high voltage power transformer? UNIT - Explain treeing. Explain tracking. State paschen s law. 4 Give the statement of townsend criteria. REMEMBER Explain primary ionization process. 6 Explain secondary ionization process. 7 Define mean free path REMEMBER 8 Explain photo ioization 9 Write the expression for breakdown from townsend s crteris. 0 Define time lag of breakdown. REMEMBER Draw the pd curve from paschen s law. REMEMBER Give the classification of liquid di-electrics. REMEMBER Give the characteristics of liquid insulations. REMEMBER 4 Define pure and commercial liquids. ANALYZE The force experienced by solid particles in liquid according to REMEMBER suspended particle theory is ----------. 6 Give the properties of composite di-electric. REMEMBER 7 Give the examples of solid dielectric. REMEMBER 8 What is partial discharge? Explain the difference between photo ionization and photo electric emission. Explain pure and commercial liquids.
Define townsend s primary and secondary ionization coefficients and also explain breakdown criteria. 4 Explain the two conditions for collision of atom and electron for ionization one. Explain the breakdown phenomenon occurs in composite dielectrics. 6 Explain thermal breakdown in solid insulation. 7 State paschen s law and explain clearly. 8 Derive the townsend s current growth equation. 9 Explain the breakdown of solid electrics due to treeing and tracking. 0 Explain various theories of breakdown in liquids. How short term breakdown is differ from long term breakdown in composite di-electric. Explain the streamer theory of gas insulation. Explain the partial discharge phenomenon in solid insulations. 4 Explain different ionization process leading to breakdown in gas. UNIT - Write different forms of high voltage. REMEMBER Draw half wave rectifier circuit. REMEMBER Draw full wave rectifier circuit. REMEMBER 4 Draw voltage doubler circuit. REMEMBER Draw COCKROFT WALTON circuit. REMEMBER 6 Write the expression of output from COCKROFT WALTON REMEMBER circuit. 7 Write the expression for optimum number of stages for minimum REMEMBER voltage drop in COCKROFT WALTON circuit. 8 Draw the cascade transformer. REMEMBER 9 Draw the resonant transformer. REMEMBER 0 Draw the multi stage impulse generator. REMEMBER Define peak tp peak ripple. REMEMBER In COCKROFT WALTON circuit Vmax = V, operating frequency = 0Hz, C = 0.0µF and load current is ma, calculate optimum number of stages. In COCKROFT WALTON circuit Vmax = V, operating frequency = 0Hz, C = 0.0µF and load current is ma, calculate output voltage at optimum number of stages. 4 In COCKROFT WALTON circuit Vmax = V, operating frequency = 0Hz, C = 0.0µF and load current is ma, calculate voltage regulation. Name any two methods for measurement of high DC and AC voltages. REMEMBER 6 State Hall effect. REMEMBER
7 What are magnetic links? Draw and explain tesla coil. Explain different methods to pproduce switching voltages for testing at laboratories. Explain full wave and half wave rectifier circuits to generate high DC voltage. 4 Explain voltage doubler circuits to generate high DC voltage. Draw and explain the principle of Vandegraff generator.. 6 Draw and explain COCKROFT WALTON circuit. 7 Draw and explain cascade transformer to generate high AC voltage. 8 Draw and explain multi stage impulse generator. 9 Analyze various impulse generator circuit and explain effect of circuit inductance and small resistance on them. ANALYZE 0 Explain the principle of operation of electro-static generator. Explain any two methods for measurement of high DC voltages. ANALYZE How the principle of generating voltmeter helps in measuring high voltages? Explain any two methods for measurement of high AC voltages. ANALYZE 4 Explain the capacitive voltage transformer for high AC voltage. Explain the peak reading AC voltmeters. 6 State Hall effect and principle of operation of Hall generator. 7 Explain how measurement of high impulse currents is done using rogowski coil and faraday s generator. QUESTION BANK ON ANALYTICAL ANSWER QUESTION A COCKROFT WALTON circuit with 8 stages with all equal capacitance of 0.0 µf. The supply transformer secondary voltage is KV ata frequency of 0Hz. If the load current to be supplied is ma. Calculate ripple percentage, voltage regulation and optimum number of stages for minimum regulation. An impulse generator has 8 stages with each condenser rated for 0.6 µf and KV. The load capacitor available is 000PF. Find the series resistance and the damping resistance needed to produce./0µs impulse wave. What is the maximum output voltage of the generator, if the charging voltage in KV? A stages impulse generator has 0. µf condenser rated for 00KV. The wave front and wave tail resistance connected are.k ohms and 4K ohms respectively. If the load condenser is 000PF. Find the wave front and wave tail times of the impulse wave produced. Calculate the peak current and wave shape of the output current of the generator having the total capacitance of µf. the charging voltage is 00KV, circuit inductance.47mh and the 4 dynamic resistance of the objects is 0.0 ohms. UNIT -4 Write two sentences about lighting and switching over voltages. 4
Writing characteristics of switching surges. 4 State Ferranti effect. REMEMBER 4 4 How over voltages can be controlled due to switching. 4 Name parameters which states lighting strokes. REMEMBER 4 6 State principles for design of insulation of EHV and UHV REMEMBER 4 systems. 7 Name protective devices used against lighting strokes. REMEMBER 4 8 Classify the transmission lines. REMEMBER 4 9 What are causes of over voltages? 4 0 What are the temporary over voltages? 4 What is lighting phenomenon? REMEMBER 4 What are the different methods as protection against lighting? REMEMBER 4 Compare switching and lighting surges. ANALYZE 4 4 Mention different kinds of over voltages. REMEMBER 4 What are the mechanism by which lighting strokes develop and induce over voltages on over head power lines? 4 Explain the different aspects of insulation design and insulation co-ordination adopted for EHV systems. 4 Give the mathematical models for lighting discharges and explain them. 4 4 What are abnormal switching over voltages and why do these occur? How are these controlled in power systems? 4 What are volt-time curves? What is their significance in power 4 systems studies? 6 Explain the importance of switching over voltages in EHV power systems. How is protection against over voltages achieved? 4 UNIT - Define type and routine test. REMEMBER The resistance of insulation using loss of charge method ----------- REMEMBER -. Draw schering bridge for measurement of high charging currents. REMEMBER 4 Compare earthing and shielding. ANALYZE What are detectors used in di-electric measurements? REMEMBER 6 Write the expression for energy associated in single discharge? REMEMBER 7 Define electric and partial discharge. REMEMBER 8 Define discharge magnitude and discharge energy. REMEMBER 9 Define sensitivity and resolution. REMEMBER 0 Define discharge disruptive voltage. REMEMBER Define withstand voltage.. REMEMBER Define 0% and 00% flash over voltage. REMEMBER Define creepage distance. REMEMBER 4 What are the reference atmospheric conditions? REMEMBER
What are power frequency and impulse tests? REMEMBER Explain the insulation testing methods on bushings. Explain the insulation testing methods on isolators and circuit breakers. Explain the insulation testing methods on cables. 4 Explain the insulation testing methods on transformer. Explain the insulation testing methods on surge arrester. 6 Write short notes on radio interference measurements. 7 Write short notes on tests on insulation. Define the terminologies used in testing of insulation of power REMEMBER 8 equipment. 9 Define the important partial discharge quantities. REMEMBER 0 How do you estimate the partial discharge in power apparatus and discuss the calibration of PD detectors? ANALYZE Draw a neat diagram of high voltage schering bridge and describe various feature of the bridge. Explain how this can be used to measure the dielectric constant of a dielectric material. Explain about the measurement of dielectric constant and loss factor of insulating materials. Write short notes on loss of charge method for measurement of insulation resistance. 4 Define all the terminology used in partial discharge phenomenon. REMEMBER Explain various methods to determine the volume resistivity of s solid dielectric material. 6 Explain the balanced and straight detection methods for locating the partial discharge in a solid insulating system. QUESTION BANK ON ANALYTICAL ANSWER QUESTION A schering bridge was used to measure the capacitance and loss angle of a HV bushing. At balance the observation were: The value of standard condenser = 00PF, R = 80 ohms, C = 0.00µF and R4 = 66 ohms. What are the values of capacitance and loss factor of the bushing? The lossless standard capacitor used in the high voltage schering bridge has a value 00PF. In a certain measurement, the other arms of the bridge at balance are i) a resistance of 64 ohms and ii) a capacitance of 0.0 µf in parallel with a resistance of 00 ohms. Determine capacitance and loss tangent of the specimen at 0Hz. The capacitance and dissipation factor of a Bakelite sample were determined by using circular electrodes and found to be 0 PF and 0.000 respectively by schering bridge measurements. For the same electrode system the air capacitance was found to be PF. What is the complex permittivity of the sample? PREPARED BY : Mr.T.Anil Kumar