R05410204-Power System Operation and Control

Code.No: 37026

R05

SET-1

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD IV .B.TECH – I SEM REGULAR EXAMINATIONS JANUARY- 2010 POWER SYSTEM OPERATION AND CONTROL (ELECTRICAL & ELECTRONICS ENGINEERING) Time: 3hours Max.Marks:80 Answer any FIVE questions All questions carry equal marks --1.a) Explain the various factors that affect optimum operation to be considered in allocating generators of different power stations, neglect line losses. b) Explain how the incremental production cost of a thermal power station can be determined. [8+8] 2. a) Assume any relevant data and notation, derive the transmission loss formula. b) Discuss about the optimum generator allocation without line losses. [8+8] 3. a) Explain about spinning reserve in hydro power plants. b) Explain about Co-ordination in hydro thermal system.

[8+8]

4. a) Derive the transfer function of speed governing system? b) Explain turbine model with block diagram?

[8+8]

5.a) What is flat frequency control? Explain its requirements. b) A 500 MW generator has speed regulation of 4%. If the frequency drops by 0.12Hz with unchanged reference, determine the increase in turbine power. Also find by how much the reference power setting be changed if the turbine power remain unchanged. [8+8] 6.a) Explain how the tie-line power deviation can be unincorporated in two-area system block diagram. b) What are the features of the dynamic response of a two area system for step load disturbances? [8+8] 7.a) Explain economic dispatch control problem in detail. b) Explain how the frequency error in the load frequency control problem is reduced to zero. [8+8] 8.a) Explain about the losses that occur due to VAR flow in power system. b) Explain how the generators act as VAR sources in a power network. [8+8]

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Code.No: 37026

R05

SET-2

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD IV .B.TECH – I SEM REGULAR EXAMINATIONS JANUARY- 2010 POWER SYSTEM OPERATION AND CONTROL (ELECTRICAL & ELECTRONICS ENGINEERING) Time: 3hours Max.Marks:80 Answer any FIVE questions All questions carry equal marks --1.a) Explain input – output characteristics of thermal power stations. b) Define in detail cost curve of thermal stations.

[8+8]

2.a) Explain with neat diagram the physical interpretation of Co-ordination equation. b) Explain various uses of general loss formula and state the assumptions made for the Calculations of Bm coefficients. [7+9] 3. In a two plant operation system, the hydro plant is operating for 8 hrs. During each day and the steam plant is operated all over the day. The characteristics of the steam and Hydro plants are. 2 CT = 0.04 PGT + 30 PGT + 20 Rs/hr 3 2 Wµ = 0.0012 PGH + 7.5 PGH m

Sec When both plants are running, the power flow from steam plant to load is 190MW and the total quantity of water is used for the hydro plant operation during 8hrs is 220 × 106 m 3 . Determine the generation of hydro plant and cost of water used. Neglect the transmission losses. [16]

4.a) Explain the necessity of maintaining a constant frequency in power system operation. b) Two generators rated 100MW and 400MW are operating in parallel. The drop characteristics of their governors are 2% and 4% respectively from no-load to full load, Assuming that the generators are operating at 50Hz at no-load, how would a load of 500MW be shared between them? What will be the system frequency at this load? Assume free governor operator. [6+10] 5.a) Explain in detail the importance of load frequency problem. b) A 100MVA synchronous generator operates on full load at a frequency of 50Hz. The load is suddenly reduced to 50 MW. Due to time log in governor system, the steam value begins to close after 0.4 seconds. Determine the change in frequency that occurs in this time. Given the initial constant H = 5 KW – Sec/KVA of generator rating. [8+8] 6. Two power stations A and B operate in parallel. They are inter connected by a short Transmission line. The station capacities are 100MW and 200MW respectively. The Generators ‘A’ and ‘B’ have speed regulations of 3% and 2% respectively. Calculate the output of each station and load on the interconnection, if

a) The load on each station is 125MW. b) The load on respective bus bars is 60MW and 190MW c) The load is 150MW at station a bus bar only

[16]

7.a) Obtain the dynamic response of lead frequency controller with integral control action in single area frequency control. b) Distinguish between load frequency control and economic dispatch control. [8+8] 8.a) Write short notes on compensated and un-compensated transmission lines. b) Explain briefly about the shunt and series compensation of transmission systems. [8+8]

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Code.No: 37026

R05

SET-3

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD IV .B.TECH – I SEM REGULAR EXAMINATIONS JANUARY- 2010 POWER SYSTEM OPERATION AND CONTROL (ELECTRICAL & ELECTRONICS ENGINEERING) Time: 3hours Max.Marks:80 Answer any FIVE questions All questions carry equal marks --1.a) Explain production cost and incremental fuel cost b) Explain hydro-thermal scheduling problem.

[8+8]

2.a) Discuss the general problem of economic operation of large inter connected area. b) What are the factors that can be taken into consideration for scheduling of generators in a plant? [8+8] 3. Using dynamic programming method, how do you find the most economical combination of the units to meet a particular load demand?

[16]

4. Draw the block diagram of a power system showing the governor, turbine and synchronous generator, indicating their transfer functions. For a step disturbance of ∆PD , obtain the response of “increment in frequency” making suitable assumptions. a) Without proportional plus integral controller and b) With proportional plus integral control [8+8] 5. a) Explain about control area and control area error. b) Two generators of rating 100MW and 200MW are operating with drop characteristic of 6% from no-load to full load. Determine the load shared by each generator, if a load of 270MW is connected across the parallel combination of these generators. [8+8] 6.a) What are the advantages of inter connected operation of power system? Explain. b) Two areas of a power system network are inter connected by a tie-line, whose capacity is 500MW, operating at a power angle of 350 . If each area has a capacity of 5000MW and the equal speed regulation of 3Hz/puMW, determine the frequency of oscillation of the power for step change in load. Assume that both areas have the same inertia constants of H = 4 Sec [8+8] 7. Explain the optional design of load frequency control problem. What are limitations of optional control theory in designing the load frequency control problem? [16] 8. a) Describe in detail off load and on load top changing transformers. b) Discuss in detail about the generation and absorption of reactive power in power system components. [8+8] -oOo-

Code.No: 37026

R05

SET-4

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD IV .B.TECH – I SEM REGULAR EXAMINATIONS JANUARY- 2010 POWER SYSTEM OPERATION AND CONTROL (ELECTRICAL & ELECTRONICS ENGINEERING) Time: 3hours Max.Marks:80 Answer any FIVE questions All questions carry equal marks --1. a) Explain in detail about incremental heat rate curve and cost curve b) Write the expression for hourly loss of economy resulting from error incremental cost representation. [8+8] 2. The incremental fuel cost for two plants are dC1 = 0.075 PG1 + 18 Rs./MWh dPG1 dC2 = 0.08 PG 2 + 16 Rs./MWh dPG 2 The loss coefficients are given as B11 = 0.0015/MW, B12 = -0.0004/MW and B22 = 0.0032/MW for λ = 25 Rs./MWh. Find the real power generator, total load demand and the transmission power.

[16]

3. Derive the co-ordination equation for the optimal scheduling of hydro thermal inter connected power plants. [16] 4. Explain the state-space model of synchronous machine.

[16]

5. A generator in single area load frequency control has the following parameters: Total generator capacity = 2500MW Normal operating load = 1500MW Inertia constant = 5KW – Seconds per KVA; load damping constant, B = 1%; frequency, f = 50Hz; and speed regulation, R = 2.5Hz/PU MW. If there is a 1.5% increase in the load, find the frequency drop a) Without governor control b) With governor control [8+8] 6. a) What are the features of the dynamic response of a two area system for step load disturbances? b) What are the considerations in selecting the frequency bias parameters? [8+8]

7. Show that the critical gain magnitude of integral controller of a load frequency control system in terms of system parameters is given by f0 Ki, Critical = 8H

⎡1 ⎤ ⎢⎣ R + B ⎥⎦

2

[16]

8. a) A single – phase motor connected to a 230V, 50Hz supply takes 30A at a Pf of 0.7 lag. A capacitor is shunted across the motor terminal to improve the Pf to 0.9 lag. Determine the capacitance of the capacitor to be shunted across the motor terminals. b) Explain the specifications of load compensation. [8+8]

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