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(Pages : 2 ) Name ………....................... Reg. No………........................ M M.TECH. DEGREE EXAMINATION Model Question Paper - II First Semester Branch: Electrical Engineering Specialization: Power Electronics and Power Systems MEEPP 106-3 HIGH VOLTAGE DC TRANSMISSION (Elective-1) (2013 Admission onwards) (Regular) Time: Three Hours 1 Maxm. 100 Marks (a) What are the advantages of HVDC when compared to HVAC. [13] (b) Classify different types of HVDC systems based on : i. Construction ii. Application OR 2 3 [12] (a) How is HVDC economical when compared to HVAC for bulk power transmission. [10] (b) How is power flow control achieved in HVDC systems. [08] (c) Explain the choice of DC voltage for a fixed amount of power transfer . [07] (a) Draw the Graetz circuit and draw the timing diagram considering the overlap greater than 60° and without overlap for i. Voltage across the load ii. Voltage across any two conducting pair of valves (b) Explain the dependency of power factor angle on firing angle (α) [15] . [10] OR 4. (a) Derive the expression for output voltage across the load for a firing angle less than 60° in the 3-ph bridge circuit. [08] (b) Draw the Graetz circuit and draw the timing diagram considering the overlap less than 60° and without overlap .Also draw the waveforms of Current in any phase . Specify the assumptions made. [07] (c) Explain Design requirements of a converter circuit. Show that 3-phase bridge configuration is the most suitable for HVDC link. [10] 5. (a) Explain constant-voltage parallel scheme and constant current series scheme for multi terminal DC lines. [10] (b) Why is constant current control preferred over constant voltage control [08] (c) Explain real and reactive power control during steady state and transient conditions [07] OR 6. (a) Explain in detail control characteristics of Converter in HVDC system. [13] (b) Explain in detail the reactive power requirement of a converter station. How is the reactive power supplied? [12] 7. (a) Derive the expression for ripple current in the DC current. Draw the waveform of ripple voltage and ripple current for α=30° [13] (b) What are the effects of Harmonics on the communication systems like telephone line. [12] OR 8. (a) What are the different scenarios where HVDC lines are subjected to over-voltages. Explain in brief the different overvoltage protection schemes. [13] (b) Explain in detail the DC line oscillations and the line dampers used. [12] -***-