Solution for High Voltage Engineering - BRAINHEATERS for High Voltage Engineering ... Measurement of High Value DC Current by Fall- Generator. ... Multistage Impulse Generators Marx

Mumbai University Electrical (Semester -III)

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Solution for High Voltage Engineering

December 2015

Index

Q.1)

a) ………………………………………………………………………….2

b) ……………………………………… ………………………………….3

c) ………………………………………………………………………….4-6

d) ………………………………………………………………………….7

e)…………………………………………………………………………. 8-9

Q.2)

a) …………………………………………………………………………. 10-11

b) …………………………………………………………………………. 12-17

Q.3)

a) …………………………………………………………………………. 17-21

b) ………………………………………………………………………….22- 25

Q.4)

a) …………………………………………………………………………. 26-29

b) …………………………………………………………………………. N.A

Q.5)

a) ………………………………………………………………………….30

b) ………………………………………………………………………….31-32

Q.6)

a) ………………………………………………………………………….33-36

b) …………………………………………………………………………. 36-40



Q1Attmpt any four

(a) What are electronegative gases? Why is the breakdown strength higher

in these gases compared to that in other gases. (05)

Ans: Break Down in Electro negative Gases :-



(b) Explain the phenomenon of tracking in solid insulating materials under

the electrical stress. How it can be minimized.

Ans: Breakdown Due to Treein g and Tracking



(c) With a neat sketch explain trigatron spark gap used in impulse

generators. (05)

Ans :- Tripping and Control Impulse Generators







(d) What are commercial liquid dielectrics, and how are they different from

pure liquid dielectric ? (05)

Ans: Pure Liquids



(e) With a neat sketch explain Hall Generators for measurements of high

current. (05)

Ans: Measurement of High Value DC Current by Fall- Generator





Q2

(a) Explain with neat diagrams the principal of operation of an Electrostatic

voltmeters .Discuss its advantages and limitation on high voltage

measurements. (10)

Ans: Electrostatic Voltmeter





(b) Why is Cockcroft-Walton circuit preferred for voltage multiplier circuits ?

Explain its working with a schematic diagram. (10)

Ans: Cockroft Walton Voltage Multiplier Circuit







(5) Similarly C1’ must acquire for stability reasons a charge 3q so that it can

supply a charge q to the load and 2 q to capacitance C2 in next half cycle

(6) During the transformer cycle shown in figure (b) .the diodes D1 ,D2 , D3

conduct when B is positive with respect to A.









Q3)(a)What is Paschen’s law? How to do account for the optimum voltage for

breakdown under a gi ven ‘p X d condition? (10)

Ans :- Paschens Law

It state that , “Breakdown voltage of uniform filed gap is unique function of

product of p , i.e gas pressure and d i.e. electrode gap distance for a

particular gas and for a given electrode material”

According to Townsends breakdown Criteria γ and α both are function of E/P









(b)Describe in brief various tests carried out on overhead line insulators.

Testing Insulator :-









Q4(a) Explain how a sphere gap can be used to measure the peak value of

voltages.What are the parameters and factors that imfluence such voltage

measurement?

Ans: Sphere Gap Meter







(b) In an experiment in a certain gas it was found that the steady state current

is 5.5 x 10-8 A at 8KV at 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 x 10-19 A.Calculate Townsend’s primary ionization coefficient

alpha. (10)

Ans: N.A.



Q5(a) Explain the various theories that explain breakdown in commercial liquid

dielectric . (10)

Ans: Conduction and Breakdown Commercial Liquids



(b) What is ‘thermal breakdown ’ in solid dielectric ,and how is it practically

more significant than other mechanism. (10)

Ans: Thermal Breakdown





Q6(a) Describe the construction principle of operation and application of 3-

state Marx generator circuit . (10)

Ans: Multistage Impulse Generators Marx Circuit







(b)What are the various factors to be considered while designing a high

voltage laboratory . (10)

Ans: Classification of HV Laboratories

1)A small size Labpratory

2)Medium Size Laboratory









Documents

Solution for High Voltage Engineering - BRAINHEATERS for High Voltage Engineering ... Measurement of High Value DC Current by Fall- Generator. ... Multistage Impulse Generators Marx