Thursday, March 1, 2012
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B.E./B.Tech. DEGREE EXAMINATION,APRIL/MAY 2010
VI - SEMESTER
B.E. ELECTRICAL AND ELECTRONICS ENGINEERING
EE339 - POWER SYSTEM ANALYSIS
Time: 3hrs Max Marks: 100
Answer all Questions
PART – A (10 x 2 = 20 Marks)
1. What is the need for system analysis in planning and operation of power system?
2. How are the base values chosen in per unit representation of a power system?
3. Draw the equivalent circuit of a transformer with off-nominal tap ratio and admittance .
4. Define bus incidence matrix.
5. Mention two objectives of short circuit analysis.
6. Draw the zero sequence network of a star connected generator with zero sequence impedance Zgo when the neutral is grounded through an impedance Zn.
7. What are the three classes of buses of a power system used in power flow analysis? What are the quantities to be specified and to be computed for each class during power flow solution?
8. Compare Gauss-Seidel method and Newton – Raphson method with respect to
number of iterations taken for convergence and memory requirement.
9. Define critical clearing time.
10. Write the power-angle equation of a synchronous machine connected to an infinite bus and also the expression for maximum power transferable to the bus.
PART B (5 x 16 = 80 Marks)
11. Obtain the per unit impedance (reactance) diagram of the power system
Generator No.1: 20 MVA, 10.5 KV, X'' = 1.4 ohms, Xn1= 0.5 ohm
Generator No.2: 10 MVA, 6.6 KV, X"= 1.2 ohms, Xn2 = 0.5 ohm
Transformer T1 (3 phase): 10 MVA, 33/11 kV, X = 15.2 ohms per phase on high tension side.
Transformer T2 (3 phase) : 10 MVA, 33/6.2 kV, X= 16 ohms per phase on high tension side.
Transmission line: 22.5 ohms / phase.
Choose a common base of 20 MVA
12.a) Determine Z bus using bus impedance matrix building algorithm by adding the lines as per increasing element number. The reactance diagram of the system is shown in
(OR)
12.b) Explain the modelling of Generator, Load and Transmission line for short circuit, power flow and stability studies.
13.a) Derive the formula for fault current, fault-bus voltages and current through the lines for a 3 phase symmetrical fault at a bus in a power system using Z bus. State the assumptions made in the derivation.
(OR)
13.b) A single line to ground fault occurs on bus 4 of the system shown in Figure. Q.13(b)
(i) Draw the sequence networks.
Generator 1 & 2 : 100 MVA, 20kV with X1 = X2 = 20%, X0 = 4%, Xn = 5%
Transformer 1 & 2 : 100 MVA, 20kV/345kV. X leakage = 8% on 100 MVA.
Transmission line: X1 = X2 =15% and X0 =50% on a base of 100 MVA, 20kV
14.a) Explain clearly the algorithmic steps for solving load flow equations using Newton – Raphson method (polar form) when the system contains all types of buses. Assume that the generators at the P-V buses have enormous Q limits and hence Q limits need not be checked.
(OR)
14.b) The system data for a load flow problem are given in Table 1 and Table 2.
(i) Compute Y bus
(ii) Determine bus voltages at the end of 1st iteration by Gauss-Seidel method. Take acceleration factor as 1.6.
Bus Code of Lines Admittance (p.u)
1-2 2-j8
1-3 1-j4
2-3 0.6-j2.6
TABLE – 1 Line Data
Bud Code P Demand in p.u Q Demand in p.u V, p.u Remarks
1 - - 1.06?0 Slack
2 0.5 0.2 - PQ
3 0.4 0.3 - PQ
TABLE – 2 Bus Data
15.a)i) Write the swing equation describing the rotor dynamics of a synchronous machine connected to infinite bus through a double circuit transmission line.
ii) Explain the step-wise procedure of determining the swing curve of the above system using Modified Euler's method.
(OR)
15.b) In the system shown in Fig, Q. 15(b) a 3 phase fault occurs at point P closer to bus 2.
Find the critical clearing angle for clearing the fault with simultaneous opening of the breakers 1 & 2. The reactance values of the various components are Xg = 0.15 p.u Xtr=0.1 p.u, XL1 = 0.5 p.u, XL2 = 0.4 p.u. The generator is delivering 1.0 p.u power at the instant preceding the fault.
B.E./B.Tech. DEGREE EXAMINATION,APRIL/MAY 2010
VI - SEMESTER
B.E. ELECTRICAL AND ELECTRONICS ENGINEERING
EE339 - POWER SYSTEM ANALYSIS
Time: 3hrs Max Marks: 100
Answer all Questions
PART – A (10 x 2 = 20 Marks)
1. What is the need for system analysis in planning and operation of power system?
2. How are the base values chosen in per unit representation of a power system?
3. Draw the equivalent circuit of a transformer with off-nominal tap ratio and admittance .
4. Define bus incidence matrix.
5. Mention two objectives of short circuit analysis.
6. Draw the zero sequence network of a star connected generator with zero sequence impedance Zgo when the neutral is grounded through an impedance Zn.
7. What are the three classes of buses of a power system used in power flow analysis? What are the quantities to be specified and to be computed for each class during power flow solution?
8. Compare Gauss-Seidel method and Newton – Raphson method with respect to
number of iterations taken for convergence and memory requirement.
9. Define critical clearing time.
10. Write the power-angle equation of a synchronous machine connected to an infinite bus and also the expression for maximum power transferable to the bus.
PART B (5 x 16 = 80 Marks)
11. Obtain the per unit impedance (reactance) diagram of the power system
Generator No.1: 20 MVA, 10.5 KV, X'' = 1.4 ohms, Xn1= 0.5 ohm
Generator No.2: 10 MVA, 6.6 KV, X"= 1.2 ohms, Xn2 = 0.5 ohm
Transformer T1 (3 phase): 10 MVA, 33/11 kV, X = 15.2 ohms per phase on high tension side.
Transformer T2 (3 phase) : 10 MVA, 33/6.2 kV, X= 16 ohms per phase on high tension side.
Transmission line: 22.5 ohms / phase.
Choose a common base of 20 MVA
12.a) Determine Z bus using bus impedance matrix building algorithm by adding the lines as per increasing element number. The reactance diagram of the system is shown in
(OR)
12.b) Explain the modelling of Generator, Load and Transmission line for short circuit, power flow and stability studies.
13.a) Derive the formula for fault current, fault-bus voltages and current through the lines for a 3 phase symmetrical fault at a bus in a power system using Z bus. State the assumptions made in the derivation.
(OR)
13.b) A single line to ground fault occurs on bus 4 of the system shown in Figure. Q.13(b)
(i) Draw the sequence networks.
Generator 1 & 2 : 100 MVA, 20kV with X1 = X2 = 20%, X0 = 4%, Xn = 5%
Transformer 1 & 2 : 100 MVA, 20kV/345kV. X leakage = 8% on 100 MVA.
Transmission line: X1 = X2 =15% and X0 =50% on a base of 100 MVA, 20kV
14.a) Explain clearly the algorithmic steps for solving load flow equations using Newton – Raphson method (polar form) when the system contains all types of buses. Assume that the generators at the P-V buses have enormous Q limits and hence Q limits need not be checked.
(OR)
14.b) The system data for a load flow problem are given in Table 1 and Table 2.
(i) Compute Y bus
(ii) Determine bus voltages at the end of 1st iteration by Gauss-Seidel method. Take acceleration factor as 1.6.
Bus Code of Lines Admittance (p.u)
1-2 2-j8
1-3 1-j4
2-3 0.6-j2.6
TABLE – 1 Line Data
Bud Code P Demand in p.u Q Demand in p.u V, p.u Remarks
1 - - 1.06?0 Slack
2 0.5 0.2 - PQ
3 0.4 0.3 - PQ
TABLE – 2 Bus Data
15.a)i) Write the swing equation describing the rotor dynamics of a synchronous machine connected to infinite bus through a double circuit transmission line.
ii) Explain the step-wise procedure of determining the swing curve of the above system using Modified Euler's method.
(OR)
15.b) In the system shown in Fig, Q. 15(b) a 3 phase fault occurs at point P closer to bus 2.
Find the critical clearing angle for clearing the fault with simultaneous opening of the breakers 1 & 2. The reactance values of the various components are Xg = 0.15 p.u Xtr=0.1 p.u, XL1 = 0.5 p.u, XL2 = 0.4 p.u. The generator is delivering 1.0 p.u power at the instant preceding the fault.
Thursday, March 1, 2012 by Vinoth · 0
click here to download
B.E/B.TECH DEGREE EXAMINATION,APRIL/MAY 2011
sixth semester
(electrical and electronics engineering)
EE2355 DESIGN OF ELECTRICAL MACHINES
(Regulation 2008) Time:3hours Max.marks:100
sixth semester
(electrical and electronics engineering)
EE2355 DESIGN OF ELECTRICAL MACHINES
(Regulation 2008) Time:3hours Max.marks:100
Answer All Questions
PART A (10*2=20)
1.What is specific electric loading?
2.How materials are classified according to their degree of magnetism?
3.Name any two methods to reduce armature reaction.
4.What is slot loading?
5.Give the relationship between emf per turn and kva rating in a transformer .
6.What are the factors affecting the choice of flux density of core in a transformer?
7.How crawling can be prevented by design in an induction motor?
8.Define dispersion coefficient of an induction motor?
9.What is runaway speed of synchronous machine?
10.Give the need for damper winding in a synchronous machine?
PART B (16*5=80)
11.(a).Discuss about various duties and ratings of rotating machines and give their respective temperature -time curves? (16)
(OR)
(b).A field coil has a heat dissipation surface of 0.15m^2 and length of mean turn 1 m.it dissipates loss of 150W ,the emissivity being 34W/m^2_*c.Estimate the final steady temperature rise of the coil and its time constant if the cross section of the coil is 100*50mm^2,specific heat of copper is 390J/kg*c.The space factor is 0.56.Copper weighs 8900kg/m^3. (16)
12.(a) (i)Explain the effects of choice of no.of poles in a DC machine on (1)Frequency of flux reversals (2)Weight of iron(3) Weight of copper and(4) length of commutator.
(ii) A 5kw,250 v,4 pole,1500 rpm DC shunt generator is designed to have a square pole face. The specific electric loadings are 0.42Wb/m^2 and 15000AC/m respectively.Find the main dimensions of the machine.Assume full load efficiency =0.87 and pole arc to pole pitch ratio is 0.66. (8)
(OR)
(b)(i) Discuss various methods to determine the mmf required for teeth of an Electric machine.
(ii)Determine the apparent flux density in teeth of a DC machine if the real flux density in teeth is 2.15Wb/m^2,slot pitch is 28mm,slot width is 10mm,gross core length is 0.35m,no.of ventilating ducts is 4 each 10mm wide.Magnetizing force corresponding to flux density of 2.15Wb/m^2 is 55000AT/m and iron stacking factor is 0.9 (8)
13.(a)(i) Derive the output equation of a three phase transformer.(8)
(ii)The ratio of full load mmf in a 400kva,50Hz single phase core type transformer is 2.4*10^-6.Calculate the net iron area of the transformer if the maximum flux density in the core is 1.3Wb/m^2,current density in the core is 1.3 Wb/mm^2 and window space factor is 0.26.also calculate the lad mmf. (8)
(OR)
(b) A 2500 kva,6600/400v three phase core type transformer has a total loss of 4800W at full load, The transformer tank is 1.25 m in height and 1m*0.5m in plan. design a suitable scheme for tubes if the average temperature rise is to be limited to 35*c.The diameter of each tube is 50mm and are spaced 75 mm from each other. the average height of tubes is 1.05 mm.Specific heat dissipation due to radiation due to radiation and convection is respectively 6 and 6.5Wb/m^2-*c.assume that convection is improved due to the provision of tubes. (16)
14. (a) Determine the main dimensions,number of radial ventilating ducts,number of stator slots and turns per phase of a 3.7 kw,three phase,400v4 pole,50Hz squirrel cage induction motor t be started by a star delta starter.Given that the average flux density in the air gap =0.45Wb/m^2;ampere conductors per metre of armature periphery=23000 full load efficiency =0.85,full load power factor=0.84 and Kw=0.9555.tale L/r=1.5. (16)
(OR)
(b).(i)Discuss the factors to be considered in estimating the length of air gap of Induction motor. (8)
(ii)Discuss the step by step procedure to design the rotor of a squirrel cage Induction motor. (8)
15.(a) Define short circuit ratio.Explain how it is determined for an alternator.Also discuss its effects on the performance of alternator. (16)
(OR)
(b)(i) Derive the output equation of an AC machine.
(ii)Determine the main dimensions of a 100kva,50Hz,3 phase 375rpm alternator. The average gap flux density is 0.55Wb/m^2 and ampere conductors per metre is 28000.Given that L/r must be between 1 to 5. The maximum permissible peripheral speed is 50m/sec.the run away speed is 1.8 times the synchronous speed. (16)
PART A (10*2=20)
1.What is specific electric loading?
2.How materials are classified according to their degree of magnetism?
3.Name any two methods to reduce armature reaction.
4.What is slot loading?
5.Give the relationship between emf per turn and kva rating in a transformer .
6.What are the factors affecting the choice of flux density of core in a transformer?
7.How crawling can be prevented by design in an induction motor?
8.Define dispersion coefficient of an induction motor?
9.What is runaway speed of synchronous machine?
10.Give the need for damper winding in a synchronous machine?
PART B (16*5=80)
11.(a).Discuss about various duties and ratings of rotating machines and give their respective temperature -time curves? (16)
(OR)
(b).A field coil has a heat dissipation surface of 0.15m^2 and length of mean turn 1 m.it dissipates loss of 150W ,the emissivity being 34W/m^2_*c.Estimate the final steady temperature rise of the coil and its time constant if the cross section of the coil is 100*50mm^2,specific heat of copper is 390J/kg*c.The space factor is 0.56.Copper weighs 8900kg/m^3. (16)
12.(a) (i)Explain the effects of choice of no.of poles in a DC machine on (1)Frequency of flux reversals (2)Weight of iron(3) Weight of copper and(4) length of commutator.
(ii) A 5kw,250 v,4 pole,1500 rpm DC shunt generator is designed to have a square pole face. The specific electric loadings are 0.42Wb/m^2 and 15000AC/m respectively.Find the main dimensions of the machine.Assume full load efficiency =0.87 and pole arc to pole pitch ratio is 0.66. (8)
(OR)
(b)(i) Discuss various methods to determine the mmf required for teeth of an Electric machine.
(ii)Determine the apparent flux density in teeth of a DC machine if the real flux density in teeth is 2.15Wb/m^2,slot pitch is 28mm,slot width is 10mm,gross core length is 0.35m,no.of ventilating ducts is 4 each 10mm wide.Magnetizing force corresponding to flux density of 2.15Wb/m^2 is 55000AT/m and iron stacking factor is 0.9 (8)
13.(a)(i) Derive the output equation of a three phase transformer.(8)
(ii)The ratio of full load mmf in a 400kva,50Hz single phase core type transformer is 2.4*10^-6.Calculate the net iron area of the transformer if the maximum flux density in the core is 1.3Wb/m^2,current density in the core is 1.3 Wb/mm^2 and window space factor is 0.26.also calculate the lad mmf. (8)
(OR)
(b) A 2500 kva,6600/400v three phase core type transformer has a total loss of 4800W at full load, The transformer tank is 1.25 m in height and 1m*0.5m in plan. design a suitable scheme for tubes if the average temperature rise is to be limited to 35*c.The diameter of each tube is 50mm and are spaced 75 mm from each other. the average height of tubes is 1.05 mm.Specific heat dissipation due to radiation due to radiation and convection is respectively 6 and 6.5Wb/m^2-*c.assume that convection is improved due to the provision of tubes. (16)
14. (a) Determine the main dimensions,number of radial ventilating ducts,number of stator slots and turns per phase of a 3.7 kw,three phase,400v4 pole,50Hz squirrel cage induction motor t be started by a star delta starter.Given that the average flux density in the air gap =0.45Wb/m^2;ampere conductors per metre of armature periphery=23000 full load efficiency =0.85,full load power factor=0.84 and Kw=0.9555.tale L/r=1.5. (16)
(OR)
(b).(i)Discuss the factors to be considered in estimating the length of air gap of Induction motor. (8)
(ii)Discuss the step by step procedure to design the rotor of a squirrel cage Induction motor. (8)
15.(a) Define short circuit ratio.Explain how it is determined for an alternator.Also discuss its effects on the performance of alternator. (16)
(OR)
(b)(i) Derive the output equation of an AC machine.
(ii)Determine the main dimensions of a 100kva,50Hz,3 phase 375rpm alternator. The average gap flux density is 0.55Wb/m^2 and ampere conductors per metre is 28000.Given that L/r must be between 1 to 5. The maximum permissible peripheral speed is 50m/sec.the run away speed is 1.8 times the synchronous speed. (16)
by Vinoth · 3
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