Approved by AICTE, Accredited by NBA, Affiliated to JNTU, KAKINADA

SWARNANDHRA COLLEGE OF ENGINEERING & TECHNOLOGY

(Approved by AICTE, Accredited by NBA, Affiliated to JNTU, KAKINADA)

SEETHARAMPURAM,NARSAPUR-534280.W.G.DT.,

DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

Faculty Name: Mr.Ch.VENKATESWARA RAO

Class: IV B-Tech(EEE-A&B)

Subject: H.V.E

MID-II

UNIT-5

1. A) What is Rogowski Coil? Explain with a neat diagram its principle of operation for measurement of high impulse currents. M[10]

B) A Rogowski coil is required to measure impulse current of 8 kA having rate of change of

current of 1010 A/sec. The voltmeter is connected across the integrating circuit which reads 8 volts for full scale deflection. The input to the integrating circuit is from the Rogowski Coil. Determine the

mutual inductance of coil R and C of the integrating circuit. M [10]

2. What are the requirements of a sphere gap for measurement of high voltages? Discuss the disadvantages of sphere gap for measurements. M [20]

3. A) Discuss various methods of measuring high impulse currents. M [12]

B) A peak reading voltmeter is required to measure voltage upto 150 kV. The peak voltmeter

uses an RC circuit, a microammeter and a capacitance potential divider. The potential divider has a

ratio of 1200 : 1 and the micrometer can read upto 10 μA. Determine the value of R and C if the time

constant of RC circuit is 8 secs. M [8]

4. A) What are the problems associated with measurement of very high impulse voltages? Explain how these

can be taken care of during measurements. M [12]

B) An absolute electrostatic voltmeter has a movable circular plate 8 cms in diameter. If the

distance between the plates during a measurement is 4 mm, determine the potential difference when the force of attraction is 0.2 gm wt. M[8]

5. Write a short notes on

A) surge recorder M[10]

B) voltage divider M[10]

6. A) A generating voltmeter is required to measure voltage between 15 kV to 250 kV. If the

indicating meter reads a minimum current of 2 μA and maximum of 35 μA, determine the capacitance of the generating voltmeter. Assume that the speed of driving synchronous motor is 1500 rpm. M [10]

B) Determine the breakdown voltage for air gaps of 2 mm and 15 mm lengths under uniform

field and standard atmospheric conditions. Also, determine the voltage if the atmospheric pressure

is 750 mm Hg and temperature 35°C. M [10]

UNIT-6

1.Give the mathematical models for lighting discharge & explain them. M[20]

2 . how a fault can produce an over volage in system, explain with a necessary proof ? M[20]

3. explain the importance of switching over voltage in EHV power systems. How is protection against over voltages achieved? M[20]

4. explain with suitable figures the principles & functioning of

a) Expulsion gaps M[10]

b) protector tubes

M[10]

5.Discuss the power frequency over voltage in power systems. Explain various protection schemes

Employed to suppress the over voltages. M[20]

6. A surge of 100 kV travelling in a line of natural impedance 600 ohms arrives at a

junction with two lines of impedances 800 ohms and 200 ohms respectively. Find the surge voltages

and currents transmitted into each branch line. M[20]

UNIT-VII

1)  Explain the operation of high voltages Schering Bridge when the test specimen is grounded. M[20]

2)  How the dielectric constant and loss factor of an insulating material can Be measured under high voltage condition at power frequency? Draw the necessary circuit diagram. M[20]

3)  Briefly explain the method used for calibrating the partial discharge detectors. M[20]

4)  Describe how a fault in a long cable can be detected and located using partial discharge technique. M[20]

5)  Write a short note on the measuring impedance circuit for the estimation of practical discharge. M[20]

6)  Describe Mole’s arrangement for measuring high dissipation factors in the low frequency range. M[20]

UNIT-VIII

1)  Explain the following technologies often used in high voltage testing. M[20]

i) Disruptive discharge voltage

ii) Withstand voltage

iii) 100% flashover voltage

iv) Creepage distance

2)  List out the various tests to be carried out on insulator. M[20]

3)  Explain various tests to be carried out on a bushing. M[20]

4)  List out the various tests to be carried out on a cable. M[20]

5)  Explain with a schematic diagram method of measuring RIV of transmission line hardware. M[20]

6)  Describe the impulse current tests performed on lightning arrestors. M[20]

Prepared by verified by HOD Dept of EEE