問題一覧
1
ACSR means
Aluminum Conductor Steel Reinforced
2
In ACSR conductor, the function of steel is to
provide additional mechanical strength
3
The skin effect in coductors is due to nin uniform distribution of currrnt in it and major portion of the current is near the ___________
surface
4
The effective resistance of conductor is increased by
both A and B
5
When a conductor carries more current on the sirface as compared to core, it is due to
skin effect
6
If the specifec resistance of the conductor is inceased, what effect does it result on the skin effect?
decreasing
7
If the transmission voltage is increased, the percentage resistance drop will
decrease
8
The power transmission capacity of the transmission line is
proportional to the square of the voltage
9
For constant transmission efficiency, voltage is increased n times, the size of the conductor would be
reduced to (1/n^2) times of the original
10
To increase transmitted power over the line
any of these
11
Which of the following standard transmission system voltages is classified as High Voltage?
230 kV
12
The spacing between phase conductors of a 230 kV line is approximately
20 ft
13
An ACSR conductor has (n-1) layers around its single center strands the totak number of strands will be
3n^2 - 3n + 1
14
The transmission line inductance contributed by
the currebnt in order conductor
15
The valiu of inductance per conductor in three phase line is........ times the loop inductance for single phase lines
1/2
16
A three phase wye connected 20 MW load of 0.866 pf lagging is to be supplied by a transmission line is 138 kV. It is desired that line losses not to exceed 5 percent of the load. If the per phase resistance of the line is 0.7 ohm, what is the maxinum length of the line?
51
17
The per phase line loss in a 40 km transsmission line is not to exceed 60 KW while it is delivering 100 A per phase. If the resistivity of conductor material is 1.72×10^-8 ohm-meter. Determine the required conductor diameter
1.208 cm
18
A single phase two wore transmission line, 15 km long is made up of round conductor each of 0.8 cm in diameter, seperated from each other by 40 cm. Calculate the equivalent diameter od a fictitios hallow, thin walled copper conduxtor having the same inductance as in the original design.....
0.623 cm
19
A 155 kV line had a horizontal configuration. The distance between adjacent conductor is 9 ft. What is the goemetric meab distance of the line?
11.34 ft
20
What is the GMR of four starnds conductor with diamond formation in terms of r of individual strand?
1.692
21
A single phase transmission line is 35 km long consist of two solid round conductor, each of 0.9 cm in diameter, the conductor spacing is 2.5 m. Calculate tje inductance per conductor
46 mH
22
In practice the three phase conductor of a three phase line are seldon equilaterally. The usual unsymmetricsk spacing produces inductance in the three phases, leading to unequal voltage drop and unbalance in the line. To effect tjis imbalance the positions of the conductor are interchanged at regular intervals in the line. To effect this imlabance, the positions of the conductor are interchanged at regular inteevals in the line. This practice is known as___________
I. trasposition
Ii. Interchange
I
23
When the conductor of a three phase circuit are not spaced equilaterally, the trasposition is done to.
balance the three phases of the circuit
24
A 500 kV three ohase transposed line is composed of one ACSR 1272 MCM, 45/7 Bittern conductor per phase with horizontal conductor configuration, 35 ft spacing. The conductors have diamter if 1.345 in and GMR is 0.5328 in. Find inductance per km.
1.38 mH/km
25
The conductors are bundled primarily to
reduce reactance
26
* A 69 kV three phase transposed line is composed of one ACSR 336.4 MCM, 26/7 linnet conductor per phase with a horizontal configuration D12=D23==5ft. The conductors have a diamter of 0.721 onhes and gmr= 0.0243ft. Find the inductance per phase per kiloneter of the line
1.432 mH/km
27
A single circuit three phase transmission line is composed of four (4) ACSR, 1,272,000 cmil conductor per phase with horizotal configuration. The bundle spacing is 45 cm. and the adjacent phases are 14 m apart. Determine the inductance in millihenry per km. The GMR of the ACSR conductor is 0.0466ft
0.88929
28
The three phase untrasposed transmission line has 3.6 m horizontal spacing and a telepone line 1.2 m spacing is 4m below phase b and line are supported on the same tower. The power line carries a 60 Hz balanced current of 200 A. Find the voltage per km induced in the telepone line.
3.88 cis 60°
29
To increase the capacity of a transmission line or transmitting power, which of the following must be decreased?
Line inductance
30
The ratio of capacitance of the line to neutral and line to line capacitance of a transmission line having two conductor is
2.0
31
Charging current due to capacitance C when a single phase line is transmitting power at a voltage v and frequency w is
jwcv
32
The presence of earth alters the
Both A and B
33
If the height of transmission tower is increased
the line capacitance will decrease but line inductance will remain uncharged
34
If the height of transmission tower increased, which of the following paramaters is likely to change?
Capacitance
35
A 115 kV line has vertical configuration with 9 ft spacing. diameter of the 336.4 MCM ACSR is 0.721 inch. If the length of the line is 20 km what is the total capacitance?
0.187 uf
36
A 500 kV three phase transposed line is composed of two ACSR 636 MCM, 24/7 rook conductor per phase with horizontal conductor configuratiin, 35 ft spacing. Bundle spacingis 18 inches. The conductor have diamter of 0.977 in and GMR is 0.3924 in. Find capacitance per km
0.0107 uF/km
37
In the analysis of which the following lines shunt capacitance is neglected?
Short transmission lines
38
A 138 kV, three phase shirt ttansmission line has a per phase impedance of line 25MW load at 0?8 power factor lagging per phase. Calculate the sending end line voltage.
140.5 kV
39
A three phase 13 kV transmission line delivers 8 MVA of load. The per phase impedance of the line (0.01+j0.05) pu referred to a 13 kV, 8 MVA base. What is the voltage drop across the line?
130+j650 volts
40
If |Vs| = |Vr| = kV (three phase) and x=13 ohm per phase, What will be the maximum power transmission per phase?
28 MW
41
A 3 phase 115 kV, 60 Hz 120 km medium transmission line an impedance of Z=0.05 + j 0.45 ohms per km and shunt admittance of j3.4×10^-6 seimens per km. What is the trnasmission line equivalent constant D?
0.989+j0.001224
42
When thenload at the receiving end of a long transmission lineis removed, the sending end voltage is less than the receiving end voltage. This effect is known as
Ferranti effect
43
Shunt conductance in power transmission lines is due to leakage over the
insulators
44
The surge impedance of a transmission line differs from its characteristics impedance as surge impedance consider line
resistance of finite value
45
In the design of a distributor, which the following is the major consideration?
Voltage drop
46
The effect of corona can be detected by
all of the above
47
The square root of the ratio of line impedance and shuntbadmittance is called
surge impedance of the line
48
The rise of temperature in transmission line
decrease the stress and increase the length
49
Guy wire is used in the contruction of distribution lines fro what purpose?
Support the pole
50
The effect of wind pressure is more predominant on
supporting towers
51
Which of the following insulator will selected for high voltage application?
strain type
52
The strain type insulators used when
A and B
53
Causes of faults in power system
all of these
54
Three phase short circuit of an alternator will be ___________
maximum
55
By which of the following methods voltage of transmission can be regulated?
any of the above methods
56
by which of the following methods the protection against direct lighting strokes and high voltage sweep and waves is provided?
lighting arrester and ground wires
57
The top most conductor in a high trnasmission line is
earth conductor
58
What can usually be assumed as the driving of source voltage for fault and voltage calculations in per unit method?
1 p.u
59
Which of the following type of fault that used only the equivalent positive impedance of the circuit in the short circuit calculation?
Three phase fault
60
The hazards exists only during the period of the tine the ___________ is there
Fault
61
In a certain circuit analyses the bases chosen are 34.5 kV and 100 MVA. What is the impedance base?
11.9 ohms
62
A 345 kV transmission line has a series impedance of 4+j60 ohms and a shunt admittance of j2×10^-3 S. Using 100 MVA and 345 kV as base values, calculate the per unit admittance of the line
2.38
63
A three phase transformer is rated 8 MVA , 69/13.4 kV has series impedance of 7%, What is the new per unit impedance if the system study requires a 100 MVA base and 67 kV base.
0.928
64
at a 34.5 kV substation the available fault current is 10 p.u. What is the available fault MVA if the base MVA is 50?
500
65
The protection against overvoltage due to lighting is/are provided by________
I. used of overheated ground wires
II. used of surge arresters
II only
66
Which of the following short circuits most dangerous?
Dead short circuits
67
Which if the following equipment is used to limit short circuit current level in substation?
Series reactor
68
The interrupting current capacity of a circuit breaker is depends on
symmetrical short circuit current
69
What arrester nominal rating shall be used in a 34.5 kV grounded system?
27 kV
70
A three phase wye delta connected, 345/34.5 kV transformer has an emergency ratingn of 60 MVA. Determine the CT ratio and CT connections required fro the protection of the transformer primary & secondary
200:5 ∆ -con & 1000:5 Y-con
71
In a two port network , the circuit representation is/are
I. T-Network
II. π-Network
I only
72
For y bus system shown find Y11
3-j9
73
The protection against over voltage due to lighting is proveded by
any if the above
74
An automatic device that operates at present values is known as
relay
75
Which if the following protective device operates on the principle of Kirchoff's Current law?
Differential Protective Relay
76
What is the IEEE standard device number for Distance Relay?
21
77
Two bus system has: Z11 = j0.11565 pu, Z12 = Z21= j0.04580 and Z22 = j0.13893 pu. If an impedance Zb= j0 4 pu is connected between buses 1 and 2. Find the new value of Z22
j0.10698 pu
78
A symmetrical positive-sequence four-bus Z matrix Z11 = j0.27, Z12 = j0.24, Z13 = j0 17, Z14 = j0.20, Z22= j0.29, Z23 = j 0.20, Z24 = j0.24, Z33 = j3.0, Z34 = j0.26, and Z44 = j0.38, all in pu, what is the three-phase fault at Bus 3?
-j 3.33 p.u
79
The positive, negative and zero sequence reactance of a 20 MVA 13.2 KV synchronous generator are 0.3 pu, 0.2 pu and 0.1 pu, respectively. The generator is solidly grounded and is not loaded. A double line to ground fault occurs at the generator terminals, determine the fault current
4750 A
80
A generator having a solidly grounded neutral and rated 50 MVA, 30 kV nas X₁=25% X=15% and Xo=5% What reactance must be placed in the generator neutral to limit the fault current for a bolted line to ground fault to that for a bolted 3-phase fault?
1.8 ohms
81
At a certain point of the system network the positive, negative and zero sequence impedances are 0.25, 0.25 0.3 pu respectively. The base MVA is 100. The voltage level at that point is 34.5 kV. Determine the fault current for a line to line fault.
5797 A
82
A small factory is tapped at 13.8 kV line where the available fault MVA is 150, the line from the tapping point to the 3-333 kva transformer has an impedance of 0 5 ohm The impedance of each transformer is 4% and the secondary voltage is 230 volts what is the approximate three phase fault current at the secondary side of the transformer bank?
50,000 Amperes
83
A synchronous generator having a subtransient reactance of 0 15 pu and operating 5% above its rated voltage supplies a synchronous motor having 0.2 pu subtransient reactance The motor is connected to the generator by a transmission line and a transformer of total reactance 0 305 pu. A sudden three phase short circuit occurs at the generator terminals Determine the per unit subtransient fault current
9.079 pu
84
A Generator rated 500 MVA, 20 kv has an impedance of 0 20 per unit if the generator is supplying 425 kW load at 20 kV, unity power factor and a fault occurs at the load What will be the per unit value of the fault current with respect to the bases, 500 MVA and 20 kV
5.0
85
A certain point of 34.5 kV 3-phase system has 3-phase short circuit of 4000 with X/R ratio is 25. and line to ground short circuit MVA of 3.800 with X/R ratio of 15 What is the impedance at the utility connection point in ohms?
0.298cis 87.7°
86
Power system has receiving current of 1.2 pu or current at the receiving end 0.6 pu voltage at the receiving end and 05 pu receiving power. When the base current is 160 amp and base voltage is 20 kV what is power factor?
0.694
87
A 6000 volts line supplying three loads A, B & C. If the loads are located 4 6 and 10 km respectively away from the supply having a resistance of 0.05 ohm per km & currents la=50A, Ib=75A and Ic=100A. What is the voltage delivered in load C
5917.5 volts
88
A three phase power of 875 MVA,0.8 power factor is to be transmitted to a substation located 315 km from the source of power. For a preliminary design assume the following parameters Vs=1.0 pu, Vr=0.9 pu, wavelength of 5000 km, characteristic impedance of 320 ohms and a power angle of 36.87 degrees. Based on practical line loadability equation determine the line nominal voltage
400 kV
89
A 3-phase, 115 kV, 60 Hz 120 km medium transmission line has an impedance of Z= 0.05+j 0.45 ohm per km and shunt admittance of 13.4x10 siemens per km What is the transmission line equivalent constant D
0.989+j0.001224
90
A 69 KV, 16km, 3-phase transmission line has an impedance of 0.125 +10.4375 ohm per km Determine the transmission efficiency when the line delivers 70 MVA to a load at 64 KV with 80% pf lagging
95.90%
91
A 220 kV three phase transmission line is 40 km long. The resistance per phase is 6 ohms per phase and the inductance per phase is 20 ohms per phase. The shunt capacitance is negligible. Determine the sending end line voltage when supplying 381MVA at 0.8 power factor lagging at 220 kV
143.82+j12.4kV
92
The conductors are bundled primably to
reduce reactance
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32問 • 1年前問題一覧
1
ACSR means
Aluminum Conductor Steel Reinforced
2
In ACSR conductor, the function of steel is to
provide additional mechanical strength
3
The skin effect in coductors is due to nin uniform distribution of currrnt in it and major portion of the current is near the ___________
surface
4
The effective resistance of conductor is increased by
both A and B
5
When a conductor carries more current on the sirface as compared to core, it is due to
skin effect
6
If the specifec resistance of the conductor is inceased, what effect does it result on the skin effect?
decreasing
7
If the transmission voltage is increased, the percentage resistance drop will
decrease
8
The power transmission capacity of the transmission line is
proportional to the square of the voltage
9
For constant transmission efficiency, voltage is increased n times, the size of the conductor would be
reduced to (1/n^2) times of the original
10
To increase transmitted power over the line
any of these
11
Which of the following standard transmission system voltages is classified as High Voltage?
230 kV
12
The spacing between phase conductors of a 230 kV line is approximately
20 ft
13
An ACSR conductor has (n-1) layers around its single center strands the totak number of strands will be
3n^2 - 3n + 1
14
The transmission line inductance contributed by
the currebnt in order conductor
15
The valiu of inductance per conductor in three phase line is........ times the loop inductance for single phase lines
1/2
16
A three phase wye connected 20 MW load of 0.866 pf lagging is to be supplied by a transmission line is 138 kV. It is desired that line losses not to exceed 5 percent of the load. If the per phase resistance of the line is 0.7 ohm, what is the maxinum length of the line?
51
17
The per phase line loss in a 40 km transsmission line is not to exceed 60 KW while it is delivering 100 A per phase. If the resistivity of conductor material is 1.72×10^-8 ohm-meter. Determine the required conductor diameter
1.208 cm
18
A single phase two wore transmission line, 15 km long is made up of round conductor each of 0.8 cm in diameter, seperated from each other by 40 cm. Calculate the equivalent diameter od a fictitios hallow, thin walled copper conduxtor having the same inductance as in the original design.....
0.623 cm
19
A 155 kV line had a horizontal configuration. The distance between adjacent conductor is 9 ft. What is the goemetric meab distance of the line?
11.34 ft
20
What is the GMR of four starnds conductor with diamond formation in terms of r of individual strand?
1.692
21
A single phase transmission line is 35 km long consist of two solid round conductor, each of 0.9 cm in diameter, the conductor spacing is 2.5 m. Calculate tje inductance per conductor
46 mH
22
In practice the three phase conductor of a three phase line are seldon equilaterally. The usual unsymmetricsk spacing produces inductance in the three phases, leading to unequal voltage drop and unbalance in the line. To effect tjis imbalance the positions of the conductor are interchanged at regular intervals in the line. To effect this imlabance, the positions of the conductor are interchanged at regular inteevals in the line. This practice is known as___________
I. trasposition
Ii. Interchange
I
23
When the conductor of a three phase circuit are not spaced equilaterally, the trasposition is done to.
balance the three phases of the circuit
24
A 500 kV three ohase transposed line is composed of one ACSR 1272 MCM, 45/7 Bittern conductor per phase with horizontal conductor configuration, 35 ft spacing. The conductors have diamter if 1.345 in and GMR is 0.5328 in. Find inductance per km.
1.38 mH/km
25
The conductors are bundled primarily to
reduce reactance
26
* A 69 kV three phase transposed line is composed of one ACSR 336.4 MCM, 26/7 linnet conductor per phase with a horizontal configuration D12=D23==5ft. The conductors have a diamter of 0.721 onhes and gmr= 0.0243ft. Find the inductance per phase per kiloneter of the line
1.432 mH/km
27
A single circuit three phase transmission line is composed of four (4) ACSR, 1,272,000 cmil conductor per phase with horizotal configuration. The bundle spacing is 45 cm. and the adjacent phases are 14 m apart. Determine the inductance in millihenry per km. The GMR of the ACSR conductor is 0.0466ft
0.88929
28
The three phase untrasposed transmission line has 3.6 m horizontal spacing and a telepone line 1.2 m spacing is 4m below phase b and line are supported on the same tower. The power line carries a 60 Hz balanced current of 200 A. Find the voltage per km induced in the telepone line.
3.88 cis 60°
29
To increase the capacity of a transmission line or transmitting power, which of the following must be decreased?
Line inductance
30
The ratio of capacitance of the line to neutral and line to line capacitance of a transmission line having two conductor is
2.0
31
Charging current due to capacitance C when a single phase line is transmitting power at a voltage v and frequency w is
jwcv
32
The presence of earth alters the
Both A and B
33
If the height of transmission tower is increased
the line capacitance will decrease but line inductance will remain uncharged
34
If the height of transmission tower increased, which of the following paramaters is likely to change?
Capacitance
35
A 115 kV line has vertical configuration with 9 ft spacing. diameter of the 336.4 MCM ACSR is 0.721 inch. If the length of the line is 20 km what is the total capacitance?
0.187 uf
36
A 500 kV three phase transposed line is composed of two ACSR 636 MCM, 24/7 rook conductor per phase with horizontal conductor configuratiin, 35 ft spacing. Bundle spacingis 18 inches. The conductor have diamter of 0.977 in and GMR is 0.3924 in. Find capacitance per km
0.0107 uF/km
37
In the analysis of which the following lines shunt capacitance is neglected?
Short transmission lines
38
A 138 kV, three phase shirt ttansmission line has a per phase impedance of line 25MW load at 0?8 power factor lagging per phase. Calculate the sending end line voltage.
140.5 kV
39
A three phase 13 kV transmission line delivers 8 MVA of load. The per phase impedance of the line (0.01+j0.05) pu referred to a 13 kV, 8 MVA base. What is the voltage drop across the line?
130+j650 volts
40
If |Vs| = |Vr| = kV (three phase) and x=13 ohm per phase, What will be the maximum power transmission per phase?
28 MW
41
A 3 phase 115 kV, 60 Hz 120 km medium transmission line an impedance of Z=0.05 + j 0.45 ohms per km and shunt admittance of j3.4×10^-6 seimens per km. What is the trnasmission line equivalent constant D?
0.989+j0.001224
42
When thenload at the receiving end of a long transmission lineis removed, the sending end voltage is less than the receiving end voltage. This effect is known as
Ferranti effect
43
Shunt conductance in power transmission lines is due to leakage over the
insulators
44
The surge impedance of a transmission line differs from its characteristics impedance as surge impedance consider line
resistance of finite value
45
In the design of a distributor, which the following is the major consideration?
Voltage drop
46
The effect of corona can be detected by
all of the above
47
The square root of the ratio of line impedance and shuntbadmittance is called
surge impedance of the line
48
The rise of temperature in transmission line
decrease the stress and increase the length
49
Guy wire is used in the contruction of distribution lines fro what purpose?
Support the pole
50
The effect of wind pressure is more predominant on
supporting towers
51
Which of the following insulator will selected for high voltage application?
strain type
52
The strain type insulators used when
A and B
53
Causes of faults in power system
all of these
54
Three phase short circuit of an alternator will be ___________
maximum
55
By which of the following methods voltage of transmission can be regulated?
any of the above methods
56
by which of the following methods the protection against direct lighting strokes and high voltage sweep and waves is provided?
lighting arrester and ground wires
57
The top most conductor in a high trnasmission line is
earth conductor
58
What can usually be assumed as the driving of source voltage for fault and voltage calculations in per unit method?
1 p.u
59
Which of the following type of fault that used only the equivalent positive impedance of the circuit in the short circuit calculation?
Three phase fault
60
The hazards exists only during the period of the tine the ___________ is there
Fault
61
In a certain circuit analyses the bases chosen are 34.5 kV and 100 MVA. What is the impedance base?
11.9 ohms
62
A 345 kV transmission line has a series impedance of 4+j60 ohms and a shunt admittance of j2×10^-3 S. Using 100 MVA and 345 kV as base values, calculate the per unit admittance of the line
2.38
63
A three phase transformer is rated 8 MVA , 69/13.4 kV has series impedance of 7%, What is the new per unit impedance if the system study requires a 100 MVA base and 67 kV base.
0.928
64
at a 34.5 kV substation the available fault current is 10 p.u. What is the available fault MVA if the base MVA is 50?
500
65
The protection against overvoltage due to lighting is/are provided by________
I. used of overheated ground wires
II. used of surge arresters
II only
66
Which of the following short circuits most dangerous?
Dead short circuits
67
Which if the following equipment is used to limit short circuit current level in substation?
Series reactor
68
The interrupting current capacity of a circuit breaker is depends on
symmetrical short circuit current
69
What arrester nominal rating shall be used in a 34.5 kV grounded system?
27 kV
70
A three phase wye delta connected, 345/34.5 kV transformer has an emergency ratingn of 60 MVA. Determine the CT ratio and CT connections required fro the protection of the transformer primary & secondary
200:5 ∆ -con & 1000:5 Y-con
71
In a two port network , the circuit representation is/are
I. T-Network
II. π-Network
I only
72
For y bus system shown find Y11
3-j9
73
The protection against over voltage due to lighting is proveded by
any if the above
74
An automatic device that operates at present values is known as
relay
75
Which if the following protective device operates on the principle of Kirchoff's Current law?
Differential Protective Relay
76
What is the IEEE standard device number for Distance Relay?
21
77
Two bus system has: Z11 = j0.11565 pu, Z12 = Z21= j0.04580 and Z22 = j0.13893 pu. If an impedance Zb= j0 4 pu is connected between buses 1 and 2. Find the new value of Z22
j0.10698 pu
78
A symmetrical positive-sequence four-bus Z matrix Z11 = j0.27, Z12 = j0.24, Z13 = j0 17, Z14 = j0.20, Z22= j0.29, Z23 = j 0.20, Z24 = j0.24, Z33 = j3.0, Z34 = j0.26, and Z44 = j0.38, all in pu, what is the three-phase fault at Bus 3?
-j 3.33 p.u
79
The positive, negative and zero sequence reactance of a 20 MVA 13.2 KV synchronous generator are 0.3 pu, 0.2 pu and 0.1 pu, respectively. The generator is solidly grounded and is not loaded. A double line to ground fault occurs at the generator terminals, determine the fault current
4750 A
80
A generator having a solidly grounded neutral and rated 50 MVA, 30 kV nas X₁=25% X=15% and Xo=5% What reactance must be placed in the generator neutral to limit the fault current for a bolted line to ground fault to that for a bolted 3-phase fault?
1.8 ohms
81
At a certain point of the system network the positive, negative and zero sequence impedances are 0.25, 0.25 0.3 pu respectively. The base MVA is 100. The voltage level at that point is 34.5 kV. Determine the fault current for a line to line fault.
5797 A
82
A small factory is tapped at 13.8 kV line where the available fault MVA is 150, the line from the tapping point to the 3-333 kva transformer has an impedance of 0 5 ohm The impedance of each transformer is 4% and the secondary voltage is 230 volts what is the approximate three phase fault current at the secondary side of the transformer bank?
50,000 Amperes
83
A synchronous generator having a subtransient reactance of 0 15 pu and operating 5% above its rated voltage supplies a synchronous motor having 0.2 pu subtransient reactance The motor is connected to the generator by a transmission line and a transformer of total reactance 0 305 pu. A sudden three phase short circuit occurs at the generator terminals Determine the per unit subtransient fault current
9.079 pu
84
A Generator rated 500 MVA, 20 kv has an impedance of 0 20 per unit if the generator is supplying 425 kW load at 20 kV, unity power factor and a fault occurs at the load What will be the per unit value of the fault current with respect to the bases, 500 MVA and 20 kV
5.0
85
A certain point of 34.5 kV 3-phase system has 3-phase short circuit of 4000 with X/R ratio is 25. and line to ground short circuit MVA of 3.800 with X/R ratio of 15 What is the impedance at the utility connection point in ohms?
0.298cis 87.7°
86
Power system has receiving current of 1.2 pu or current at the receiving end 0.6 pu voltage at the receiving end and 05 pu receiving power. When the base current is 160 amp and base voltage is 20 kV what is power factor?
0.694
87
A 6000 volts line supplying three loads A, B & C. If the loads are located 4 6 and 10 km respectively away from the supply having a resistance of 0.05 ohm per km & currents la=50A, Ib=75A and Ic=100A. What is the voltage delivered in load C
5917.5 volts
88
A three phase power of 875 MVA,0.8 power factor is to be transmitted to a substation located 315 km from the source of power. For a preliminary design assume the following parameters Vs=1.0 pu, Vr=0.9 pu, wavelength of 5000 km, characteristic impedance of 320 ohms and a power angle of 36.87 degrees. Based on practical line loadability equation determine the line nominal voltage
400 kV
89
A 3-phase, 115 kV, 60 Hz 120 km medium transmission line has an impedance of Z= 0.05+j 0.45 ohm per km and shunt admittance of 13.4x10 siemens per km What is the transmission line equivalent constant D
0.989+j0.001224
90
A 69 KV, 16km, 3-phase transmission line has an impedance of 0.125 +10.4375 ohm per km Determine the transmission efficiency when the line delivers 70 MVA to a load at 64 KV with 80% pf lagging
95.90%
91
A 220 kV three phase transmission line is 40 km long. The resistance per phase is 6 ohms per phase and the inductance per phase is 20 ohms per phase. The shunt capacitance is negligible. Determine the sending end line voltage when supplying 381MVA at 0.8 power factor lagging at 220 kV
143.82+j12.4kV
92
The conductors are bundled primably to
reduce reactance