Power System Operation and Control (1)

Code No: R41024

Set No. 1

R10

IV B.Tech I Semester Supplementary Examinations, Feb/Mar - 2015 ( Electrical and Electronics Engineering) Time: 3 hours

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POWER SYSTEM OPERATION AND CONTROL

Max. Marks: 75

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Answer any FIVE Questions All Questions carry equal marks ***** 1. a) Sketch the heat rate curve and cost curve of thermal power plants and explain the significance of them. b) Explain the procedure for optimal generation allocation between the thermal generators in a thermal plant.

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2. a) Derive the transmission line loss formula and explain its importance. b) Discuss the merits and demerits of a method in which optimal generation allocation of a thermal plant including losses are considered. 3. a) Discuss the procedure for optimal allocation of generation among the hydrothermal systems. b) Discuss the demerits of hydrothermal coordination in optimal generation scheduling. 4. What is dynamic programming approach? Solve the unit commitment problem using dynamic programming with a suitable example. 5. a) Develop the mathematical modelling of speed governing system. b) What is single area system? Explain its significance.

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6. Explain the load frequency control of a two area system and develop its block diagram. 7. Explain the role of proportional plus integral control of single area system with neat block diagram. 8. a) Discuss the merits and demerits associated with series compensators. b) Prove that the reactive power flow in a line is more dependent on the bus voltage.

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Set No. 2

R10

Code No: R41024

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IV B.Tech I Semester Supplementary Examinations, Feb/Mar - 2015

POWER SYSTEM OPERATION AND CONTROL ( Electrical and Electronics Engineering)

Max. Marks: 75

W or

Time : 3 hours

Answer any FIVE Questions All Questions carry equal marks ***** 1. a) What is incremental fuel cost? Explain how it is plotted and explain its inference. b) Derive the conditions for optimal power allocation between the generators in a thermal power plant neglecting losses.

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2. a) Derive the conditions for optimal allocation of generation among the generators in a thermal plant including transmission losses. b) Consider the two bus system as shown in below figure. The incremental production costs at the two generating stations are

dc1 dc2  0.005 p1  5 and  0.004 p2  7 dp1 dp2

The B - Coefficien ts are given in matrix form as

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 0.0002 B - 0.00005

2

1

P2

Pd2

Pd1

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P1

- 0.00005 0.0003 

Determine the penalty factors at both the buses and also the approximate penalty factors. Given λ = 8 Rs/MWh.

3. a) What type of hydro plants are considered for optimal operation of hydro thermal system? Explain. b) Explain the advantages of hydrothermal coordination in generation allocation.

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Code No: R41024

R10

Set No. 2

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4. a)What is unit commitment? Explain how it can be done when hydro thermal generators are available. b) Discuss the importance of spinning reserve requirements in the solution of unit commitment problem.

5. a) With neat diagram, explain the different parts of a speed governing system. b) Determine the area frequency response characteristics and the static frequency error for a system with the following data, when 1% load change occurs. B = 0.01 P.u MW/Hz R = 2.5 Hz/P.u MW Tp = 16 sec Kp = 100Hz/p.u MW

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6. a) Explain how the tie line power deviation can be incorporated in two area system block diagram. b) Two control areas having the following characteristics R1 = 0.011 p.u B1 = 0.85 p.u Base MVA = 1000 Area-2 R2 = 0.018 p.u B2 = 0.95 p.u Base MVA = 1000 A load change of 200 MW occurs in area -1. Find the new steady state frequency.

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Area-1

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7. Discuss the importance of combined load frequency control and economic dispatch control with a neat block diagram. 8. a) Explain the objectives of reactive power compensation in a transmission system. b) Explain the behaviour of an uncompensated transmission line under load.

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R10

Code No: R41024

Set No. 3

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IV B.Tech I Semester Supplementary Examinations, Feb/Mar - 2015

POWER SYSTEM OPERATION AND CONTROL ( Electrical and Electronics Engineering)

Max. Marks: 75

W or

Time: 3 hours

Answer any FIVE Questions All Questions carry equal marks ***** 1. a) Sketch the input and output characteristic of a thermal plant and explain its significance. b) Write an algorithm for optimal power generation in a thermal power plant neglecting transmission losses.

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2. a) Describe the strategy for generation allocation in a thermal power plant optimally when including the line losses. b) A two bus system with load at bus 2 only. If 50MW is transmitted from plant 1 to load at bus 2 over the line, the loss is 2.5MW. The incremental production costs at both the plants are dc1 dc2  0.03P1  15 and  0.05P2  20 dp1 dp2

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The value of λ is 23 Rs/MWh. Find the generation schedule for economy with losses coordinated. What will be the generation schedule if the losses are not coordinated but considered.

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3. a) What is short term hydro thermal scheduling? Explain the difficulties present in the short term hydro thermal scheduling. b) Explain the effect of line losses on the optimal hydro thermal scheduling. 4. a) What is unit commitment? Explain how it can be done when only thermal power generators are available. b) Discuss briefly various constraints imposed while solving unit commitment problem.

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Set No. 3

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Code No: R41024

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5. a) Draw the block diagram representation of an isolated power system and explain each block. b) Explain the steady state analysis of an isolated power system.

6. a) Represent the two area system in block diagram form and explain its control under load disturbances. b) Two control areas having the following characteristics Area-1 R1 = 0.01 p.u B1 = 0.8 p.u

Base MVA = 1000 Area-2

R2 = 0.015 p.u B2 = 0.9 p.u

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Base MVA = 1000

A load change of 150 MW occurs in area -2. Find the tie line power deviation. 7. Explain clearly about proportional plus integral load frequency control with a block diagram and also prove that the steady state change in frequency deviation is zero.

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8. a) Derive the relation between reactive power flow and the voltage of bus. b) Explain the effect of shunt compensation on the transmission line performance.

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R10

Code No: R41024

Set No. 4

ld

IV B.Tech I Semester Supplementary Examinations, Feb/Mar - 2015

POWER SYSTEM OPERATION AND CONTROL ( Electrical and Electronics Engineering)

Max. Marks: 75

W or

Time: 3 hours

Answer any FIVE Questions All Questions carry equal marks ***** 1. a) Discuss the various factors which will decide the production cost of a thermal plant. b) Explain the effect of neglecting the transmission losses on the optimal generation allocation of a thermal plant.

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2. a) What is a penalty factor in economic scheduling? Explain its significance. b) The fuel inputs to two plants are given by F1 = 0.015+16P1+50 and F2 = 0.02+12P2+30 The loss coefficients of the system are B11 = 0.005, B12 = 0.0012 and B22 = 0.002 MW-1. The load to be met is 200 MW. Determine the economic operating schedule and the corresponding cost of generation if the line losses are coordinated.

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3. a) Why hydrothermal coordination is required? Explain its need briefly. b) Using Legrangian multiplier develop mathematical expressions for the solution of economic hydrothermal scheduling problem.

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4. Using dynamic programming method to determine the most economical units to be committed to supply a load of 6MW. There are three units with the following data. 1 2 C1 = 0.9 P1  23P1 2 1 2 C1 = 0.5P2  22 P2 2 1 2 C1 = 0.6 P3  21P3 2 The maximum and minimum limits for each unit are 5MW and 1 MW respectively.

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Code No: R41024

R10

Set No. 4

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5. a) Derive the model of a speed governing system and represent it by a block diagram. b) Two generators with rating 100 MW and 300MW operate at 50Hz frequency. The system load increases by 100 MW when both the generators are operating at about half of their capacity. The frequency then falls to 49.5 Hz. If the generators are to share the increased load is proportion to their ratings. What should be the individual regulations expressed in actual as well as per unit. 6. a) What is area frequency response characteristic? Discuss it in the context of two area system. b) Two interconnected areas A and B have capacities 2000 MW and 750 MW respectively. The speed regulation coefficients are 0.1 p.u for both the areas on their own area ratings. The damping torque coefficient are 1.0 p.u also on their own base. Determine the steady state change in system frequency when a load increment of 50MW occurs in area A. System frequency is 50Hz.

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7. a) Explain the effect of proportional controller on a single area system. b) Discuss the requirements of the control strategies in LFC

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8. a) What are the specifications of a load compensator? b) Explain the effect of series compensation on the transmission line performance.

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