Name of the College : Dr. Navalar Nedunchezhiyan College of engineering
University : Anna University Chennai
Subject Code/Name : EE1003-High Voltage Engineering
Dept : ELECTRICAL AND ELECTRONICS ENGINEERING
Degree : B.E
YEAR/SEM: : III/VI
Website : drnnce.ac.in
Document Type : Question Bank
Download Model Question Paper : https://www.pdfquestion.in/uploads/drnnce.ac.in/3207-new%20QBhve3year.pdf
Drnnce High Voltage Engineering Question Paper
UNIT – I
OVER VOLTAGES IN ELECTRICAL POWER SYSTEMS :
PART-B (2 MARKS)
21.Why protection of transmission line important** (AU-NOV/DEC2009)
It is essential for electrical power engineers to reduce the number of outages and preserve the continuity of service and electric supply.
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22. What are the causes of over voltages in electric system** (AU-NOV/DEC2004,2005,2009,APR/MAY2005,MAY/JUNE2006,2007, NOV/DEC2013)
** Lightning over voltages
** Switching over voltages
23.How does switching over voltage originate?
Switching over voltages originate in the system itself by connection and disconnection of circuit breaker contact or due to initiation or interruption of faults.
24.What is Iso keraunic level** (AU-APR/MAY2010)
Isokeraunic level is defined as the number of days in a year when thunder is heard or recorded in particular location.
25.What are the factors that influence the lightning induced voltage on transmission lines?
** The ground conductivity
** The leader stroke current
** Corona
26.How is transmission lines classified?( AU-NOV/DEC2004)
** Lines with no loss or ideal lines
** Line without distortion or distortion less with small losses
** Lines with infinite and finite length defined by all the four parameters
27.Define attenuation and distortion.
The decrease in the magnitude of the wave as it propagates along the line is called attenuation.The elongation or change of wave shape that occurs is called distortion.
28.How is attenuation and distortion caused** (AU-MAY/JUNE2009)
Attenuation is caused due to the energy loss in the line an distortion is caused due to to the inductance and capacitance of the line.
29.What are the causes for the change of induction on transmission line?
The changes in the inductance are due to the skin effect, the proximity effect and non-uniform distribution effect of the currents and the nearness to steel structures.
30.What are the causes for the change of capacitance on transmission line?
The variation in capacitance is due to capacitance change in the insulation nearest to the ground structures, etc.
31.What is the effect of corona on transmission lines** (AU-NOV/DEC2010)
The effect of corona is to reduce the crest of the voltage wave under propagation, limiting the peak value to the critical corona voltage. Hence, the excess voltage above the critical voltage will cause power loss by ionizing the surrounding air.
32.What are the principles observed in the lattice diagram?( AU-MAY/JUNE2008)
All waves travel down hill, i.e, into the positive time. The position of the wave at any instant is given by means of the time scale at the left of the lattice diagram. The total potential at any instant of time is the super position of all the waves which arrive at that point until that instant of time, displaced in position from each other by time intervals equal to the time difference of their arrival/Attenuation is included so that the amount by which a wave is reduced is taken care. The previous history of the wave, if desired can be easily traced. If the computation is to be carried out at a point where the operations cannot be directly placed on the lattice diagram, the arms can be numbered and the quantity can be tabulated and computed.
33.Define corona. (AU- APR/MAY2005)
The traveling wave is divided into a number of sections corresponding to different voltage levels, each voltage level corresponding to a different velocity of propagation since each lamination ionizes a different capacitance. Hence, a distortion is caused in the wave shape.
34.What are the components of switching surges?
Switching surges may include high natural frequencies of the system, damped normal frequency voltage component or the restriking and recovery voltage of the system with successive reflected waves from terminations.
35.How does switching surges cause damage to circuit breaker?
In circuit breaking operation, switching surges with a high rate of rise of voltage may cause repeated restriking of the arc between the contact of a circuit breaker, thereby causing destruction of the circuit breaker contacts.