POWER SEMICONDUCTOR BASED ELECTRIC DRIVES

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1 POWER SEMICONDUCT BASED ELECTRIC DRIVES [Time: 3 Hrs] [Max. Marks: 80] Instructions: Solve any six questions from Q.No (1 or 2), Q.No (3 or 4), Q.No (5 or 6), Q.No (7 or 8), Q.No (9 or 10), Q.No (11 or 12). Use of Nonprogrammable calculator is permissible. Assume suitable data wherever necessary. Q 1. a) What are the various components of electrical drive? Hence explain the function of all components in detail. b) A motor is used to drive a hoist. Motor characteristics are given by: Quadrants I & II : T = N, N-m Quadrants III & IV: T = N, N-m Where, N is speed in rpm. When hoist is loaded, the net load torque TL=100N-m and when it is unloaded net load torque TL= - 80N-m. Obtain the equilibrium speeds for operation in all the four quadrants. Q 2. a) Explain in brief four quadrant operation of Hoist drive. b) What are the various components of load torque? Derive the fundamental torque equation for an equivalent motor load system. Q 3. a) Explain two quadrant controls of SEDC motors using chopper. b)a drive has following parameters: J= 10 Kg-m2, T= N, N-m, passive load torque TL= 0.05N, N-m where N is the speed in rpm. Initially the drive is operating in steady state. Now it is to be reversed. For this, motor characteristics is changed to T= N, N-m. Calculate the time of reversal. Q 4. a) Write a short note on power factor improvement in power semi-conductor based dc drives. b) A drive has the following parameter: T = N, N-m where N is speed in rpm. Load torque TL= 100 N-m. Initially the drive is operating in steady state. The characteristics of load torque are changed to TL = N-m. Calculate the initial and final equilibrium speeds. Q 5. a) Explain cycloconverter control of induction motor. b) Explain Current source inverter control of induction motor. Compare it with Voltage source inverter control of induction motor. Q 6. a) Explain Static Scherbius drive. b) Draw a neat circuit diagram and explain the working of Fractional hp motors. Q 7. a) Explain the starting of large synchronous motor. b) Explain in detail synchronous motor drive using cyclo converter. Q 8. a) Explain current source inverter fed synchronous motor drive. b) A 3 Φ synchronous motor rated 6600V,6pole,8 M50Hz unity power factor is star connected with parameters as: Rs = 0 and Xs = 2.8 Ω is controlled by load commutated inverter which in turn is fed from a line commutated inverter operating in a self-controlled mode with a constant v/f ratio. Source voltage is 6.6 KV, 50 Hz; load commutated inverter operates at constant firing angle of α1=1400 and rectifying angle of 00. DC link inductor resistance Rd= 0.1 Ω. Determine source side converter firing angle for regenerative breaking operation of 500rpm and rated motor current. Also calculate power supplied to the load. Q 9. a) Write a short note on solar pump drive. b) Draw the circuit diagram and explain the operation of a battery powered dc motor drive for an electric vehicle. Q 10. a) Write a short note on Stepper motor and also explain its features. b) Describe the operation of a bipolar brushless dc motor drive and explain its advantages over unipolar drive. Q 11. a) Explain in brief 25KV ac traction using transformer with tap changer. b) Explain 25KV traction employing 2 stage converters & feeding dc motor (with ckt. Diagram & waveform)

2 Q 12.a) Explain DC motor drive employing voltage source inverter fed induction motor drive. How composite braking is carried out. b) Explain AC traction drive using PWM voltage source inverter induction motor drive using provision of dynamic braking. Subject Teacher H.O.D. Principal Ms. Monica Mankar Prof. Pravinkumar Jangle Prof. V.G. Parhate ELECTRICAL DRIVES AND CONTROL [Time: 3 Hrs] [Max. Marks: 80] Instructions: Solve any six questions from Q.No (1 or 2), Q.No (3 or 4), Q.No (5 or 6), Q.No (7 or 8), Q.No (9 or 10), Q.No (11 or 12). Use of Nonprogrammable calculator is permissible. Assume suitable data wherever necessary. Q 1. a) What is The Factors That Decide the Power Handling Capacity of AC Transmission Lines? b) Power of 1500 MW Is To Be Transferred From Chandrapur Power Station to Mumbai Over a Distance Of 800 Km At A Voltage Level Of 400Kv AC. Determine: 1) No. of EHVAC Line Required. 2) Total Line Losses. 3) Percentage Power Loss. The value or r = 0.3 Ω/Km and x = 0.33Ω/Km Q 2. a) Derive an Equation for Maxwell s Potential Co-Efficient of A Single Phase Line Considering the Effect of Ground? b) Describe In Brief The Effect Of Surface Voltage Gradient On Bundled Conductors? Q 3. a) State The Standard Transmission Voltage of EHVAC Transmission In India? Prove That Power Loss In Transmission Is Independent Of Line Length? b) Power Of 1500 MW Is To Be Transferred From Chandrapur Power Station To Mumbai Over A Distance Of 800 Km At A Voltage Level Of 400Kv AC. Determine: A) No. Of EHVAC Line Required B) Total Line Losses. C) Percentage Power Loss. (8) Q 4. a) Describe The Effect Of High Electrostatic Fields On Humans, Animals And Plants? b) A Single Conductor of 525 Kv Line Having Radius Of M Is Strung 13 M Above The Ground. Calculate: a) Corona Inception Voltage.

3 b) The Effective Radius of Conductor to Ground at an Over Voltage of 2.5 P.U. c) Capacitance of Conductor to Ground with and Without Corona. d) Corona Power Loss. Q 5. a) Explain The Effects Of Corona? What Are The Preventive Measures Against Corona? b) Write Short Note On Measuring Equipments For Electrostatic Field? Q 6. a) Write short notes on Insulation coordination of HVDC system. b) Write short notes on Cost consideration of AC harmonics? Q 7. a) Define detuning factor of filters? Give the designing criteria for single tuned filters? b) State the harmful effects of AC harmonics and DC harmonics produced in HVDC system? Q 8. a) Describe the function of MRTB and its switching sequence? b) Justify HVDC converter consumes large amount of reactive power for satisfactory operation? Q 9. a) With the help of neat diagram explain the energy equation and principle of HVDC circuit breaker? b) Explain over- voltage protection of HVDC system? Q 10. a) Describe the function of metallic return transfer breaker? b) State various methods of reactive power compensation used for HVDC system. Explain any two methods in detail? Q 11. Write Short note on (any Two): (14) 1) Configuration of AC Harmonic filters 2) Overvoltage protection of HVDC system 3) Factor to be considering the site of earth electrodes Q 12. a) A pole to earth fault occurs near the rectifier terminal of a 500kv HVDC pole. The DC Smoothing reactor has an inductance of 0.8 H. Calculate the rated switching energy required for an HVDC breaker in the DC pole. Assume the fault resistance to be 0.5 Ω. (8) b) How the commutation principle is used for HVDC CB Explain. Prof. A Kamadi Prof.P.K.Jangle Prof.V.G.Parhate Subject Teacher HOD [EE] Principal SWITCHGEAR AND PROTECTION [Time: 3 Hrs] [Max. Marks: 80] Instructions: Solve any six questions from Q.No (1 or 2), Q.No (3 or 4), Q.No (5 or 6), Q.No (7 or 8), Q.No (9 or 10), Q.No (11 or 12). Use of Nonprogrammable calculator is permissible.

4 Assume suitable data wherever necessary. Q. l a). What do you mean by primary and back up protection? Explain the types of back up protection. b). Explain the terms sensitivity and selectivity with respect to their use in the protective relaying field. or Q. 2 a). Discuss the fundamental requirements of the protective relaying. b). Explain in short: What is meant by an external and internal fault? Why are adjacent zones made to overlap? Why speed of protection is important. Q. 3 a). Explain briefly the role of protection in power system. Explain the nature and causes of fault. (5) b). what do you mean by TSM and PSM? The rating of an over current relay is 5 A. PSM = 1.5, TSM = 0.4, CT ratio = 400/5, Fault current = 6000 A. Determine the operating time of the relay. At TSM = 1, operating times at various PSM are: (8) PSM Operating time in Sec Q. 4 a). A radial feeder is shown in fig. is protected by IDMT relays. The maximum and minimum ` fault 0.14( TSM) Top = sec 0.02 current is indicated in the diagram. The relay characteristic is given by the equation PSM - 1 allowing overload of 35% compute the settings of all the relays. b). Compare the time current characteristics of inverse, very inverse and extremely inverse over Current relays. Discuss their area of applications. (4) Q. 5 a) Define directional relay angle. Draw the phasor diagram and circuit to achieve quadrature connection of directional over current relay. b) What is carrier aided distance protection scheme? Explain its principle and carrier blocking distance protection scheme. (9) Q. 6 a) Draw the impedance, reactance and MHO characteristics to protect 100% of the line having (3 + j7) Ω impedance. A fault may occur at any point on the line through a resistance of 2.2 ohms. Determine the maximum percentage of line section which can be protected by each type of relay. b) Explain three step distance protection scheme using mho relay with the help of suitable example and contact diagram. Q. 7.(a) A star-connected 3-phase 10 MVA, 6.6 kv alternator is protected by Merz - price circulating current principle using 1000/5 amperes current transformers. The star point of the alternator is earthed through a resistance of 7.5 Ω. If the minimum operating current for the relay is 0.5 A, calculate the percentage of each phase of the stator winding which is unprotected against earth-faults when the machine is operating at normal voltage.

5 (b) What is magnetizing inrush current of transformer? Explain the protection against magnetizing inrush current of transformer. Q. 8.(a) A 5 MVA, 6.6 kv/400 V transformer is connected in /Y. It is protected by % differential relay. The continuous current carrying capacity of pilot wires is 1 amp. Compute C.T. ratio on both sides. (b) Define following with reference to percentage different relay: Operating coil setting Restraining coil setting Discrimination factor Through fault Through fault stability Stability ratio. Q. 9. (a) Explain with a circuit diagram and block diagram how Mho relay characteristics can developed using Amplitude comparator. (b) Explain the comparison between the amplitude and phase comparator. Q. 10. (a) What is current chopping? What are its effects on the system? (b) Explain what you understand by: Rated symmetrical braking current Making capacity (iii) Short time current rating Obtain their values for a 3-phase oil circuit breaker having the following data: Operating voltage = 11 kv, Breaking capacity = 500 MVA. Normal current A Q.11. Write short notes on (any TWO): (14) Buchholz relay SF6 circuit breaker Loss of excitation in generator. Q. 12. (a) Draw a neat sketch and explain construction and principal operation of minimum oil circuit breaker. (b) A circuit breaker is rated as 1500 a, 1000 MVA, 33 KV, 3 second, 3 Φ oil circuit breaker. Find rated symmetrical breaking current, rated making capacity, short time rating. Prof. P.K.Jangle Prof.P.K.Jangle Prof. V.G.Parhate Subject Teacher HOD [EE] Principal COMPUTER APPLICATIONS IN POWER SYSTEM [Time: 3 Hrs] [Max. Marks: 80] Instructions: Solve any six questions from Q.No (1 or 2), Q.No (3 or 4), Q.No (5 or 6), Q.No (7 or 8), Q.No (9 or 10), Q.No (11 or 12). Use of Nonprogrammable calculator is permissible. Assume suitable data wherever necessary. Q. 1. a) Explain in brief the following terms (1) Network graph (2) Tree of graph (3) Link (4) Cut set (5) Primitive Network. (10) b) A four bus sample system is shown in fig. Consider given ground as reference & the values mentioned as self impedances in pu. Find incidence matrices A, B &C and Zloop. (10)

6 Q. 2. a) Derive the equation for branch impedance matrix using singular transformation. (8) b) Single line diagram of a power system is shown. The positive sequence reactance of the components is marked on the diagram (12) Find: (1) The incidence matrices A, K & B (2) Verify (a) Ab Kt = U (3) YBUS by singular transformation (b) Bl = Al Kt Q. 3. The power system is represented by following single line diagram form ZBUS by algorithm. (Self impedance are in p.u are given). (20) Q. 4. For the system shown below, form the bus impedance matrix using an algorithm. Self impedances of different elements are given in the figure Select bus 3 as reference bus. Explain how the bus impedance matrix so formed can be modified if an element connected between bus 1-4 is removed from the above system.

7 (20) Q. 5. a) Show that the transformation matrix T is a unitary matrix. (4) b) Form impedance matrix in symmetrical components,, using 3 Φ algorithm for the sample system shown in fig. The reactance data for each element is given in table below. (10) Element X(1) X(2) X(0) Xg Generator A Generator B Transformer A - B Transmission Line B - C Q. 6. a) What are the different faults in a power system? Give representation of a 3 - Φ system for short circuit studies. (8) b) For a 3 - Φ to ground fault at bus P in a power system, derive an expression for (i) faulted bus voltage (2) Fault current (3) Voltages at other buses. (12) Q. 7. a) State the importance of load flow analysis in power system. List the different methods used for load flow analysis. (5) b) How are buses classified in load flow analysis? What is the significance of swing bus? (5) c) Draw the flow chart for Gauss - Seidel iterative method using YBUS for load flow studies. (10) Q. 8. a) State the assumptions made for transient stability studies. (4) b) With the help of flow chart discuss the algorithm to be used for transient study of power system which employs the modified Euler s method. c) The power transfer curve for certain power system is described the equation given below. If the pre fault power is 1pu compute the variation of δ & ω with time, assume that the fault is cleared at 0.12sec from its inception. Assume t = 0.05 sec and H = 4. Perform computations upto 0.15 sec by Modified Euler s method. Prefault power transfer equation = PeI = 2sinδ During fault power transfer equation = PeII = 0.5sinδ Post fault power transfer equation = PeIII = 1.5sinδ (10) Prof. A. C Dupare Prof.P.K.Jangle Prof. V.G.Parhate

8 Subject Teacher HOD [EE] Principal

B.E. / B.Tech. Degree Examination, April / May 2010 Sixth Semester. Electrical and Electronics Engineering. EE 1352 Power System Analysis

B.E. / B.Tech. Degree Examination, April / May 2010 Sixth Semester Electrical and Electronics Engineering EE 1352 Power System Analysis (Regulation 2008) Time: Three hours Answer all questions Part A (10