Code No: OR-23/EPS/PID
M.Tech. II-Semester Examinations, July/August-2006.
HIGH VOLTAGE D.C.TRANSMISSION
(Common to Electrical Power Systems and Power and Industrial
Time: 3 hours Max. Marks: 60
Answer any FIVE questions
All questions carry equal marks
– – –
1.a) Discuss the modern trends in DC transmission.
b) List out the merits and demerits of DC transmission.
2.a) Compare the power carrying capabilities of a 3-phase, 3-wire AC
transmission line with that of a bi-polar D.C transmission line
assuming the insulation levels and conductor size are same in
both the systems.
b) Classify the DC links and explain the operation of DC links with
3. Derive an equation for voltage a cross converter in terms of delay
angle and overlap angle from fundamentals. Draw the necessary
4. Explain how the inverter operation is obtained in HVDC converters
and obtain its equivalent circuit.
5.a) Explain how power is reversed in HVDC link.
b) Explain the merits of constant current control over constant
6. State the important basic controls required for the operation of
HVDC systems and explain how they work in maintaining system
stability under abnormal conditions.
7. What do you understand by characteristic harmonics in HVDC
system? Using Fourier analysis obtain an expression for nth
harmonic voltage on the DC side of the converter system. Also
discuss the effect of variation of ‘α ’ and ‘ µ ’ on the magnitude of
the above harmonics.
8.a) What are the AC harmonic filters and give their configuration and
b) Explain the DC power modulation scheme used in interconnected
operations of AC and DC systems.