Paragraph: A thermal power plant produces electric power of 600 ~kW at 4000 ~V , which is to be transported to a place 20 ~km away from the power plant for consumers' usage. It can be transported either directly with a cable of large current carrying capacity or by using a combination of step-up and step-down transformers at the two ends. The drawback of the direct transmission is the large energy dissipation. In the