Code No: 25007
RR
Set No - 1
in
III B.Tech I Semester Supplimentary Examinations,Nov/Dec 2009 POWER SYSTEMS-II Electrical And Electronics Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. What is a synchronous phase shifter? How does a synchronous phase shifter helps a system to control the voltage? What are its limitations ? [16]
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2. (a) Derive the expression for the fault current and the terminal voltages for a line to ground fault which occurs at the terminals of an unloaded 3-φ alternator. Assume that the alternator has an isolated neutral. [8+8]
or
(b) A 20MVA, 11KV, 3-φ 50HZ generator has its neutral earthed through a 5% reactor .It is in parallel with another identical generator having neutral earthed through a 5% reactor. Each generator has a positive ,Negative, and Zero sequence reactances are 20%, 10%, and 15% respectively. If a line to ground short circuit occurs in the common bus bar , determine the fault current . 3. (a) What are the advantages and disadvantages of static capacitors used for power factor improvement.
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(b) Explain the effect of power factor on transmission line conductor size and KVA rating of the equipment. 4. (a) What is grading of a cable? Why it is done? List various method?
[6]
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(b) Single-core, lead sheathed cable joint has a conductor of 10mm diameter and two layers of different insulating materials, each 10mm thick. The relative permittivities are 3(inner) and 2.5(outer). Calculate the potential gradient at the surface of the conductor when the potential difference between the conductor and the lead sheathing is 60kV. [10]
[12]
(b) the string efficiency.
[4]
5. A string of suspension insulator consists of four units. The capacitance between each pin and earth is one tenth of the self capacitance of the unit. The voltage between the line conductor and earth is 100kV. Find
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(a) The voltage distribution across the each unit
6. An overhead line has the following data: span length 185m, difference in levels of supports 6.5m, conductor dia 1.82cm, weight per unit length of conductor 2.5kg/m, wind pressure 49kg/m2 of projected area. Maximum tensile stress of the conductor 4250kg/cm2 . Factor of safety 5. Calculate the allowable sag in meters at the lower support. [16] 7. (a) Derive the ABCD parameters of a nominal T represented medium length transmission line. [8+8] 1
Code No: 25007
RR
Set No - 1
(b) Define Voltage regulation of a transmission line and explain clearly the Ferranti effect with a phasor diagram. 8. (a) Define short circuit. Derive the expression for short circuit.
[8+8]
in
(b) A generating station has four bus bar sections .Each section is connected to tie bar through 20% reactors rated at 200MVA.Generators of total capacity 100MVA and 20% reactance are connected to each bus bar section. Calculate the MVA fed to a fault under short circuit condition on four bus bars.
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nt
uW
or
ld .
?????
2
Code No: 25007
RR
Set No - 2
in
III B.Tech I Semester Supplimentary Examinations,Nov/Dec 2009 POWER SYSTEMS-II Electrical And Electronics Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) What are the advantages and disadvantages of static capacitors used for power factor improvement.
ld .
(b) Explain the effect of power factor on transmission line conductor size and KVA rating of the equipment. 2. (a) Define short circuit. Derive the expression for short circuit.
[8+8]
or
(b) A generating station has four bus bar sections .Each section is connected to tie bar through 20% reactors rated at 200MVA.Generators of total capacity 100MVA and 20% reactance are connected to each bus bar section. Calculate the MVA fed to a fault under short circuit condition on four bus bars.
3. (a) Derive the ABCD parameters of a nominal T represented medium length transmission line. [8+8]
uW
(b) Define Voltage regulation of a transmission line and explain clearly the Ferranti effect with a phasor diagram. 4. (a) Derive the expression for the fault current and the terminal voltages for a line to ground fault which occurs at the terminals of an unloaded 3-φ alternator. Assume that the alternator has an isolated neutral. [8+8]
nt
(b) A 20MVA, 11KV, 3-φ 50HZ generator has its neutral earthed through a 5% reactor .It is in parallel with another identical generator having neutral earthed through a 5% reactor. Each generator has a positive ,Negative, and Zero sequence reactances are 20%, 10%, and 15% respectively. If a line to ground short circuit occurs in the common bus bar , determine the fault current .
Aj
5. An overhead line has the following data: span length 185m, difference in levels of supports 6.5m, conductor dia 1.82cm, weight per unit length of conductor 2.5kg/m, wind pressure 49kg/m2 of projected area. Maximum tensile stress of the conductor 4250kg/cm2 . Factor of safety 5. Calculate the allowable sag in meters at the lower support. [16] 6. (a) What is grading of a cable? Why it is done? List various method?
[6]
(b) Single-core, lead sheathed cable joint has a conductor of 10mm diameter and two layers of different insulating materials, each 10mm thick. The relative permittivities are 3(inner) and 2.5(outer). Calculate the potential gradient at the surface of the conductor when the potential difference between the conductor and the lead sheathing is 60kV. [10] 3
Code No: 25007
RR
Set No - 2
7. A string of suspension insulator consists of four units. The capacitance between each pin and earth is one tenth of the self capacitance of the unit. The voltage between the line conductor and earth is 100kV. Find (a) The voltage distribution across the each unit (b) the string efficiency.
[12] [4]
in
8. What is a synchronous phase shifter? How does a synchronous phase shifter helps a system to control the voltage? What are its limitations ? [16]
Aj
nt
uW
or
ld .
?????
4
Code No: 25007
RR
Set No - 3
in
III B.Tech I Semester Supplimentary Examinations,Nov/Dec 2009 POWER SYSTEMS-II Electrical And Electronics Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) What is grading of a cable? Why it is done? List various method?
[6]
ld .
(b) Single-core, lead sheathed cable joint has a conductor of 10mm diameter and two layers of different insulating materials, each 10mm thick. The relative permittivities are 3(inner) and 2.5(outer). Calculate the potential gradient at the surface of the conductor when the potential difference between the conductor and the lead sheathing is 60kV. [10]
or
2. (a) What are the advantages and disadvantages of static capacitors used for power factor improvement. (b) Explain the effect of power factor on transmission line conductor size and KVA rating of the equipment. 3. (a) Define short circuit. Derive the expression for short circuit.
[8+8]
uW
(b) A generating station has four bus bar sections .Each section is connected to tie bar through 20% reactors rated at 200MVA.Generators of total capacity 100MVA and 20% reactance are connected to each bus bar section. Calculate the MVA fed to a fault under short circuit condition on four bus bars. 4. (a) Derive the ABCD parameters of a nominal T represented medium length transmission line. [8+8] (b) Define Voltage regulation of a transmission line and explain clearly the Ferranti effect with a phasor diagram.
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5. (a) Derive the expression for the fault current and the terminal voltages for a line to ground fault which occurs at the terminals of an unloaded 3-φ alternator. Assume that the alternator has an isolated neutral. [8+8]
Aj
(b) A 20MVA, 11KV, 3-φ 50HZ generator has its neutral earthed through a 5% reactor .It is in parallel with another identical generator having neutral earthed through a 5% reactor. Each generator has a positive ,Negative, and Zero sequence reactances are 20%, 10%, and 15% respectively. If a line to ground short circuit occurs in the common bus bar , determine the fault current .
6. A string of suspension insulator consists of four units. The capacitance between each pin and earth is one tenth of the self capacitance of the unit. The voltage between the line conductor and earth is 100kV. Find (a) The voltage distribution across the each unit (b) the string efficiency.
[12] [4]
5
Code No: 25007
RR
Set No - 3
7. An overhead line has the following data: span length 185m, difference in levels of supports 6.5m, conductor dia 1.82cm, weight per unit length of conductor 2.5kg/m, wind pressure 49kg/m2 of projected area. Maximum tensile stress of the conductor 4250kg/cm2 . Factor of safety 5. Calculate the allowable sag in meters at the lower support. [16]
in
8. What is a synchronous phase shifter? How does a synchronous phase shifter helps a system to control the voltage? What are its limitations ? [16]
Aj
nt
uW
or
ld .
?????
6
Code No: 25007
RR
Set No - 4
1. (a) Define short circuit. Derive the expression for short circuit.
in
III B.Tech I Semester Supplimentary Examinations,Nov/Dec 2009 POWER SYSTEMS-II Electrical And Electronics Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? [8+8]
ld .
(b) A generating station has four bus bar sections .Each section is connected to tie bar through 20% reactors rated at 200MVA.Generators of total capacity 100MVA and 20% reactance are connected to each bus bar section. Calculate the MVA fed to a fault under short circuit condition on four bus bars.
2. What is a synchronous phase shifter? How does a synchronous phase shifter helps a system to control the voltage? What are its limitations ? [16]
or
3. (a) Derive the ABCD parameters of a nominal T represented medium length transmission line. [8+8] (b) Define Voltage regulation of a transmission line and explain clearly the Ferranti effect with a phasor diagram.
uW
4. A string of suspension insulator consists of four units. The capacitance between each pin and earth is one tenth of the self capacitance of the unit. The voltage between the line conductor and earth is 100kV. Find (a) The voltage distribution across the each unit (b) the string efficiency.
[12] [4]
nt
5. (a) What are the advantages and disadvantages of static capacitors used for power factor improvement. (b) Explain the effect of power factor on transmission line conductor size and KVA rating of the equipment.
6. (a) What is grading of a cable? Why it is done? List various method?
[6]
Aj
(b) Single-core, lead sheathed cable joint has a conductor of 10mm diameter and two layers of different insulating materials, each 10mm thick. The relative permittivities are 3(inner) and 2.5(outer). Calculate the potential gradient at the surface of the conductor when the potential difference between the conductor and the lead sheathing is 60kV. [10]
7. An overhead line has the following data: span length 185m, difference in levels of supports 6.5m, conductor dia 1.82cm, weight per unit length of conductor 2.5kg/m, wind pressure 49kg/m2 of projected area. Maximum tensile stress of the conductor 4250kg/cm2 . Factor of safety 5. Calculate the allowable sag in meters at the lower support. [16] 7
Code No: 25007
RR
Set No - 4
8. (a) Derive the expression for the fault current and the terminal voltages for a line to ground fault which occurs at the terminals of an unloaded 3-φ alternator. Assume that the alternator has an isolated neutral. [8+8]
in
(b) A 20MVA, 11KV, 3-φ 50HZ generator has its neutral earthed through a 5% reactor .It is in parallel with another identical generator having neutral earthed through a 5% reactor. Each generator has a positive ,Negative, and Zero sequence reactances are 20%, 10%, and 15% respectively. If a line to ground short circuit occurs in the common bus bar , determine the fault current .
Aj
nt
uW
or
ld .
?????
8
