RR720202-HVDC-TRANSMISSION by andhracolleges

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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
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
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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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
All Questions carry equal marks
⋆⋆⋆⋆⋆

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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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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
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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