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Roll No. ......................
Total No. of Questions: 08]. (Total No. of Pages: 03
M.Tech.
EHV AC TRANSMISSION
SUBJECT CODE: PEE - 514/ELE -510 (Elective - I)
Paper ID: [E0490]INote : Please fill subject code and paper ID on-OMRI
Time: 03 Hours-
Instruction to Candidates:
Maximum Marks: 100
1)
2)
Attempt any Five questions.
All questions carry equal marks.
Ql) (a) Discuss role ofEHV AC transIJ?ission. Also mention voltage level abovewhich transmission is of EHV-nature. Mention need of EHV ACtransmission.
(b) Estimate Line parameters for EHV-transmission with system transmissionvoltage, 750 kY.
Q2) (a) The expression of power transmission is given by
P= E E.r sinb (in MW)s xL
where symbols used express usual meaning in a transmission line ofL km. Comment on useful conclusions relating to.power-transmission.capacity ofEHV-transmission lines.
(b) A power (P) of 1000 MW is required to be transmitted over a distanceof 1000 km at voltage level of750 kY. Determine
(i) Possible number of circuits required with Es = Er with b= 30° &
(ii) The total line losses.
Comment on line losses iflevel of voltage transmission is raised to 1200kY.
',16371/859/ P.ToO.
Q3) (a) What is meant by Thermal ratings of lines and cables? Discuss the
pheno.menonof temperaturerise of conductors and their current carryin~capacIty.
(b) Discuss properties of bundled conductors and technique to obtaingeometric mean radius or equivalent radius of the bundle. If the lineconfiguration of 1200 kV EHV-lines are: N= 8, d = 4.6 cm, R = 0.6 m,obtain req. for lines.
Q4) (a) Define voltage gradients of conductors in EHV-system: Also explainsurface voltage gradient on conductors. '
(b) A sphere gap with the spheres having radii R = 0.5m hasa gap,of0.5 mbetween their surfaces. Calculate
(i) The required charges and their locations to make the potentials 100&0.
(ii) Calculate the -voltage gradient on the surface of high-voltagesphere & .
(iii) Calculate the disruptive voltage between the spheres if the potentialbreakdown of air occurs at 30 kV/cm.
Q5) (a) Write expression of Corona-loss formulae based on
(i) Voltages&(ii) Voltagegradients.
(b) For the following Line configuration, calculate Corona loss (Pc)usingPeek's formula:
r = radius of conductor = 1 cm.
H = height above ground = 5 m.f = freq. ofline = 50 Hz.
E = 1.1 E & b = 1.0
Q6) Calculate electrostatic field ofEHV-lines in following situations:
(a) Single circuit 3-phase EHV-linesand
(b) Double circuit 3-phase EHV-lines.
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Q7) (a) What are Lighting arresters and their protective characteristics? Alsodiscuss various types of arresters based on their internal structure.
(b) Two an-ester materials have the following current-voltage characteristics.
I oc (V)6
I oc (V)40'
For current variations from 100 Amp to 100,000 Amps, determine the"ratioof voltages.
Q8) Write short notes on:
(a) Design ()fEHV-lines based on steady state limits.
(b) Series & shunt compensation ofEHV-lines.
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