Question

HUIS ASR YOUR TEACHER A transmission line that has a resistance per unit length of 1200000.00 10-40/m is to be used to transmit 5.00 MW over 400 miles (6.44 x 105 m). The output voltage of the generator is 4.50 kv (rms). (a) What is the line loss if a transformer is used to step up the voltage to 101 kV (rms)? kW (b) What fraction of the input power is lost to the line under these circumstances? (c) What difficulties would be encountered on attempting to transmit the 5.00 MW at the generator voltage of 4.50 kV (rms)?

Answer 1

(a) The current is, P I = V 5.0x106 101x109 = 49.50 A The resistance in both transmission lines is, R= 20L =(2)(4.5x10+)(6.44x109) = 580 92 The loss in power is, Ploss = I²R = (49.50)’ (580) = 1421.287 kW =1421.3 kW (b) The fraction at the power is last to the line under these circumstances is, f= Ploss P 1421.287x103 5.0x10 = 0.284 (c) The current send at source voltage of 4.5 kV is, P I = V 5x10 4.5x10 =1111.11 A Hence high value of current is a big problem here. Sending such a watt power is not possible and might if the circuit is open at the other ends still the effect of current can clause damage.