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.

M-/637 .,..

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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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