Can CAT 6 be used to connect two switches at a distance of 550 meters?

CAT 5/6 cables are tested to 100 meters. Distances beyond that length are possible, but you must be aware of the amount of signal attenuation. The Gigabit cable standard states, "1 Gb/s data transfer over distances of up to 100 meters using four pairs of CAT-5 balanced copper cabling and a 5-level coding scheme." Have you considered fiber?