Question

4.21 A 138-kV, three-phase short transmission line has a per-phase impedance of (2 + j4) ?. If the line supplies a 25-MW load at 0.8 power factor lagging, calculate (a) the efficiency of transmission and (b) the sending-end voltage and power factor. Ans. (a) 98.78 percent; (b) 139.5 kV, 0.99 4.22 A three-phase short transmission line having a per-phase impedance of (2 + j4) ? has equal line-to-line receiving-end and sending-end voltages of 115 kV while supplying a load at 0.8 power factor leading. Calculate the power supplied by the line. Ans. 839.2 MW 4.23 A three-phase, wye-connected, 20-MW load of power factor 0.866 lagging is to be supplied by a transmission line at 138 kV. It is desired that the line losses not exceed 5 percent of the load. If the per-phase resistance of the line is 0.7 ?, what is the maximum length of the line? Ans. 51 km 4.24 The per-phase constants of a 345-kV, three-phase, 150-km-long transmission line are resistance = 0.1 ?/km, inductance = 1.1 mH/km, and capacitance = 0.02 ?F/km. The line supplies a 180-MW load at 0.9 power factor lagging. Using the nominal-? circuit, determine the sending-end voltage. Ans. 350.8 kV 4.25 Repeat Problem 4.24 using the nominal-T circuit. Ans. 359.3 kV

          4.21 A 138-kV, three-phase short transmission line has a per-phase impedance of (2 + j4) ?. If the line supplies a 25-MW load at 0.8 power factor lagging, calculate (a) the efficiency of transmission and (b) the sending-end voltage and power factor.
Ans. (a) 98.78 percent; (b) 139.5 kV, 0.99

4.22 A three-phase short transmission line having a per-phase impedance of (2 + j4) ? has equal line-to-line receiving-end and sending-end voltages of 115 kV while supplying a load at 0.8 power factor leading. Calculate the power supplied by the line.
Ans. 839.2 MW

4.23 A three-phase, wye-connected, 20-MW load of power factor 0.866 lagging is to be supplied by a transmission line at 138 kV. It is desired that the line losses not exceed 5 percent of the load. If the per-phase resistance of the line is 0.7 ?, what is the maximum length of the line?
Ans. 51 km

4.24 The per-phase constants of a 345-kV, three-phase, 150-km-long transmission line are resistance = 0.1 ?/km, inductance = 1.1 mH/km, and capacitance = 0.02 ?F/km. The line supplies a 180-MW load at 0.9 power factor lagging. Using the nominal-? circuit, determine the sending-end voltage.
Ans. 350.8 kV

4.25 Repeat Problem 4.24 using the nominal-T circuit.
Ans. 359.3 kV

4.21 A 138-kV, three-phase short transmission line has a per-phase impedance of (2 + j4) ?. If the line supplies a 25-MW load at 0.8 power factor lagging, calculate (a) the efficiency of transmission and (b) the sending-end voltage and power factor.
Ans. (a) 98.78 percent; (b) 139.5 kV, 0.99

4.22 A three-phase short transmission line having a per-phase impedance of (2 + j4) ? has equal line-to-line receiving-end and sending-end voltages of 115 kV while supplying a load at 0.8 power factor leading. Calculate the power supplied by the line.
Ans. 839.2 MW

4.23 A three-phase, wye-connected, 20-MW load of power factor 0.866 lagging is to be supplied by a transmission line at 138 kV. It is desired that the line losses not exceed 5 percent of the load. If the per-phase resistance of the line is 0.7 ?, what is the maximum length of the line?
Ans. 51 km

4.24 The per-phase constants of a 345-kV, three-phase, 150-km-long transmission line are resistance = 0.1 ?/km, inductance = 1.1 mH/km, and capacitance = 0.02 ?F/km. The line supplies a 180-MW load at 0.9 power factor lagging. Using the nominal-? circuit, determine the sending-end voltage.
Ans. 350.8 kV

4.25 Repeat Problem 4.24 using the nominal-T circuit.
Ans. 359.3 kV

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