RR720202-HVDC-TRANSMISSION

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       Code No: RR420202                                                Set No. 1
           IV B.Tech II Semester Supplimentary Examinations, May 2008
                              HVDC TRANSMISSION
                        (Electrical & Electronic Engineering)
       Time: 3 hours                                          Max Marks: 80
                            Answer any FIVE Questions
                          All Questions carry equal marks
                                       ⋆⋆⋆⋆⋆




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         1. (a) What are the different applications of HVDC transmission system? Explain
                them in detail.
            (b) With neat sketches explain the different kinds of D.C. links available. [8+8]

         2. Draw the circuit diagram voltage and current wave form of a 3-φ, 6 pulse uncon-
            trolled bridge rectifier and derive the expression for:

             (a) Average DC Voltage
            (b) Total VA rating of valves and transformer.                                    [8+8]

         3. Discuss in detail, the control characteristics of a converter.                     [16]

         4. Describe the method of Compensation of reactive power in HVDC substation .Draw
            simple single line schematics for each.                                    [16]

         5. Obtain the mathematical model of a d.c. network and d.c. converter, including
            converter controller.                                                    [16]

         6. Write short notes on:




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             (a) Protection against over voltages
            (b) Commutation failure in inverter
             (c) Arc through.                                                              [5+6+5]

         7. Give reasons for selecting star-star and star-delta transformer configuration instead
            of two star-star configurations for 12 pulse converter. Derive an equation for pri-
            mary current.                                                                   [16]

         8. What are the various types of filters that are employed in HVDC converter station?
            Discuss them in detail.                                                      [16]


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       Code No: RR420202                                               Set No. 2
           IV B.Tech II Semester Supplimentary Examinations, May 2008
                              HVDC TRANSMISSION
                        (Electrical & Electronic Engineering)
       Time: 3 hours                                          Max Marks: 80
                            Answer any FIVE Questions
                          All Questions carry equal marks
                                       ⋆⋆⋆⋆⋆




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         1. What is the need for interconnection of systems? Explain the merits of connecting
            HVAC systems by HVDC tie-lines?                                              [16]

         2. Draw a schematic of a 6 pulse converter circuit and derive from fundamentals, the
            expression for voltage and currents for the operation of convertor as a rectifier and
            inverter with relevant waveforms.

         3. Write short notes on the following:

            (a) Constant Alpha control
                                                                                            [16]

                                                                                             [8+8]


            (b) Inverse cosine control.

         4. With block diagram, discuss the principle of operation of a basic power controller.
                                                                                          [16]

         5. (a) Derive the mathematical model of d.c. link controllers of a d.c. link.
            (b) Write the mathematical model of a d.c. converter.                            [8+8]

         6. (a) Explain the fault clearing process in H.V.D.C. poles. Explain how are the




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                H.V.D.C. equipment protected against prolonged short circuit currents though
                there is no H.V.D.C. circuit breaker on H.V.D.C. pole side.
            (b) Explain the protection provided for DC line.                                [10+6]

         7. Write short notes on the following:                                              [8+8]

            (a) Telephone influence factor.
            (b) Harmonic distortion.

         8. What are the various types of filters that are employed in HVDC converter station?
            Discuss them in detail.                                                      [16]


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      www.andhracolleges.com The Complete Information About Colleges in Andhra Pradesh


       Code No: RR420202                                               Set No. 3
           IV B.Tech II Semester Supplimentary Examinations, May 2008
                              HVDC TRANSMISSION
                        (Electrical & Electronic Engineering)
       Time: 3 hours                                          Max Marks: 80
                            Answer any FIVE Questions
                          All Questions carry equal marks
                                       ⋆⋆⋆⋆⋆




         www.andhracolleges.com
         1. Draw a schematic diagram of a typical HVDC converter station and explain the
            functions of various components available.

         2. (a) Clearly explain how harmonics are produced and obtain the expression for
                rms value of the fundamental component of the current.
                                                                                    [16]



            (b) Obtain a relation between firing angle and power factor angle in a 3-φ bridge
                rectifier.

         3. Write short notes on the following:
                                                                                       [8+8]

                                                                                            [8+8]

            (a) Combined characteristics of Rectifier and Inverter
            (b) Constant - Minimum - Ignition -Angle Control

         4. Write a note on the following sources of reactive power:

            (a) Synchronous condensers
            (b) Static VAR system.                                                          [8+8]

         5. Derive and explain the solution of AC/DC load flow problem using simultaneous




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            method.                                                                 [16]

         6. (a) State and explain why H.V.D.C. circuit breakers are not necessary in main
                poles of H.V.D.C. system.
            (b) Sketch a complete single line diagram of D.C. side of H.V.D.C. substation and
                indicate various surge arresters.                                       [8+8]

         7. How do you estimate the harmonic order based upon pulse number of HVDC con-
            verter station? Give a detailed harmonic analysis of a 12 pulse converter for char-
            acteristic harmonics.                                                          [16]

         8. What are the various types of filters that are employed in HVDC converter station?
            Discuss them in detail.                                                      [16]


                                              ⋆⋆⋆⋆⋆




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                                              1 ofUSA-UK-Australia-Germany-France-NewZealand Universities List
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      www.andhracolleges.com The Complete Information About Colleges in Andhra Pradesh


       Code No: RR420202                                               Set No. 4
           IV B.Tech II Semester Supplimentary Examinations, May 2008
                              HVDC TRANSMISSION
                        (Electrical & Electronic Engineering)
       Time: 3 hours                                          Max Marks: 80
                            Answer any FIVE Questions
                          All Questions carry equal marks
                                       ⋆⋆⋆⋆⋆




         www.andhracolleges.com
         1. (a) What are the different applications of HVDC transmission system? Explain
                them in detail.
            (b) With neat sketches explain the different kinds of D.C. links available. [8+8]

         2. Draw the schematic diagram of a typical HVDC converter station with 2 six pulse
            converter units and explain the function of each component.                [16]

         3. With circuit diagram, explain the principle of operation of firing angle control
            scheme.                                                                   [16]

         4. What is meant by reactive power control? Explain in detail. How it is achieved.
                                                                                        [16]

         5. Obtain the mathematical model of a d.c. network and d.c. converter, including
            converter controller.                                                    [16]

         6. Explain the difference between A.C. circuit breaker and H.V.D.C. circuit breaker.
            State the principle of artificial current zero employed in H.V.D.C. circuit breakers.
            State the events occurring in the entire fault clearing process using such a breaker.




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                                                                                            [16]

         7. What is the reason for using star-star and star-delta transformer configurations for
            12 pulse converter. Derive an equation for primary current using fourier analysis.
                                                                                          [16]

         8. Derive an equation for harmonic voltage and current for single tuned filter and
            discuss the influence of network admittance on design aspects.             [16]


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