A 250 kV power transmission line carrying 5.00 ✕ 102 A is hung from grounded metal towers by ceramic insulators, each having a 2.00 ✕ 109 Ω resistance. (a) What is the resistance to ground in ohms of 145 of these insulators? (Assume the insulators are connected in parallel.) Ω (b) Calculate the power in watts dissipated by 145 of them. W (c) What fraction of the power carried by the line is this? P Ptot =
a)
Resistance to the ground when 145 insulators are connected in
parallel is,
Reff = R/145
Where Reff is the combined resistance of 145 insulators with
resistance R.
Reff = (2 x 109) / 145
= 1.38 x 107 Ohm
b)
Power dissipated, P = V2/Reff
= (250 x 103)2 / (1.38 x
107)
4531.25 W
c)
Total power carried by the lines, Ptot = VI
= 250 x 103 x 5 x 102
= 1250 x 105 W
Fraction of total power carried by insulators = P/Ptot
= 4531.25 W / (1250 x 105 W)
= 3.63 x 10-5
A 250 kV power transmission line carrying 5.00 ✕ 102 A is hung from grounded metal...
1. A power transmission line is hung from metal towers with glass insulators having a resistance of 2.55 ✕ 109 Ω. What current (in mA) flows through the insulator if the voltage is 280 kV? (Some high-voltage lines are DC.) 2. A charge of 6.50 C passes through a pocket calculator's solar cells in 2.00 h. What is the power output (in W), given the calculator's voltage output is 4.50 V?
(1) A large lightning bolt had a 20,500 A current and moved 32.5 C of charge. What was its duration (in ms)? (2) A power transmission line is hung from metal towers with glass insulators having a resistance of 2.55 ✕ 109 Ω. What current (in mA) flows through the insulator if the voltage is 280 kV? (Some high-voltage lines are DC.)
A thee-phase short transmission line is supplying a load of 250 MW at 0.8 power factor lagging. The voltage at the receiving end is kept constant at 230 kV. The resistance and reactance per phase of the line are 5Ω and 15 Ω respectively. (i) Calculate the voltage regulation. (ii) At what value of the power factor is the voltage regulation zero? Derive the expression used