Final answer:
A long transmission line typically means lengths longer than 250 km for high voltage AC power lines, as capacitance and inductance effects become significant. Lines at 60 Hz can have long wavelength electromagnetic waves reaching 6000 km, which can lead to energy loss. High voltages, usually in the hundreds of kilovolts, minimize these losses.
Step-by-step explanation:
In the context of power transmission, a long transmission line typically refers to a length where capacitance and inductance of the line cannot be neglected in the transmission line model. While there is no definitive length at which a transmission line is considered 'long', generally lines of more than 250 kilometers (about 150 miles) could fall into this category. For 60 Hz AC transmission lines, they exhibit extremely long wavelength electromagnetic waves that can reach lengths of about 6000 km. These waves are one source of energy loss in long-distance power transmission, and it's important to note that high voltages are used to reduce these losses.
In dealing with long-distance transmission, it is crucial to maintain high voltages often in the range of hundreds of kilovolts. A voltage of 480 V would be considered unreasonably low for long-distance power transmission.