Power is usually transmitted over long distances as alternating current (AC). Th

Question

Power is usually transmitted over long distances as alternating current (AC). The reason for this is that AC transformers can easily be used to "step-up" the voltage for transmission, and then "step-down" to supply to residences, whereas DC transformers are complicated and costly. Why is it preferable to transmit at high voltage (typically the frequency used is 60 Hz)? For very long distances the conducting cables actually start to gain a significant capacitance (for example, a typical copper 5 mile long cable would have a capacitance of 2.4 microFarad), which adds to the total impedance. In order to minimize the reactance of the above transmission cable, what would you have to do?

Explanation / Answer

It is preferable to transmit at high voltage to minimize the high signal loss .

In order to minimize the reactance of the above transmission cable , signal is to be transmitted at high frequency .

As, Xc = 1/(2pi * f * C)

Thus, higher is the frequency of signal lower will be capacitive reactance .

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