If you get down to the technical part, an ordinary extension cord is a transmission line. It's not normally thought of in this fashion but it could be. You see the high voltage power transmission lines going across country. There are power transmission lines going through your neighborhood. These may be on poles or underground. The wires in your house are also power transmission lines. This could include your extension cord. They allo transmit the household power to where it's needed. It's just semantics, but thinking of an extension cord as a transmission line is valid.
