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Question
Give the advantage of AC in long distance power transmission with an illustration.
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Solution
- When power is transmitting for long-distance a fraction of power is lost due to joule heating (I2R).
- This power loss can be tackled either by reducing current i or by reducing resistance R of a transmission line.
- At the transmitting point, voltage is increased and the current is decreased by a step-up transformer.
- This reduced current at high voltage reaches the destination without applicable loss.
- At the receiving point, voltage is decreased and current is increased by step down transformer.
- Example 1:
2MW power is transmitted at 40Ω with 10 kV voltage
I = `"P"/"V" = (2 xx 10^6)/(10 xx 10^3)` = 200 A
Power loss = I2 R = (200)2 × 40 = 1.6 × 106 W
% of Power loss = `(1.6 xx 10^6)/(2 xx 10^6) xx 100 % = 80%` - Example 2:
When 2MW power at 40 Q is transmitted with 100 kV voltage.
I = `"P"/"V" = (2 xx 10^3)/(100 xx 10^3)` = 20 A
Power loss = I2 R = (200)2 × 40 = 0.016 × 106 W
% of power loss = `(0.016 xx 10^6)/(2 xx 10^6) xx 100%`
= 0.8 × 100% = 80%
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