An AC power generator produces 50 A (rms) at 3600 V. The voltage is stepped up to 100 000 V by an ideal transformer and the energy is transmitted through a long-distance power line which has a resistance of 100 ohms. What percentage of the power delivered by the generator is dissipated as heat in the long-distance power line?

Respuesta :

Given:

[tex]I_{rms} = 50 A[/tex]

voltage, V = 3600V

step-up voltage, V' = 100000 V

Resistance of line, [tex]R = 100\ohm[/tex]

Solution:

To calculate % heat loss in long distance power line:

Power produced by AC generator, P = [tex]50\times 3600[/tex] W

P = 180000 W = 180 kW

At step-up voltage, V = 100000V or 100 kV

current, I = [tex]\frac{P}{V'}[/tex]

I = [tex]\frac{1800000}{100000}[/tex]

I = 1.8 A

Power line voltage drop is given by:

[tex]V_{drop} = I\times R[/tex]

[tex]V_{drop} = 1.8\times 100[/tex]

[tex]V_{drop} = 180 V[/tex]

Power dissipated in long transmission line [tex]P_{dissipated} = V_{drop}\times I[/tex]

Power dissipated in long transmission line [tex]P_{dissipated} = 180\times 1.8[/tex] = 324 W

% Heat loss in power line, [tex]P_{loss} = \frac{P_{dissipated}}{P}\times 100[/tex]

% Heat loss in power line, [tex]P_{loss} = \frac{324}{180000}\times 100[/tex]

[tex]P_{loss} = 0.18%[/tex]

 

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