The function of the actual circuit breaker - to interrupt current - is not different, although the mechanical construction changes quite a bit when you need to

The function of the actual circuit breaker - to interrupt current - is not different, although the mechanical construction changes quite a bit when you need to interrupt both very high currents and extinguish the high-voltage arc created when you interrupt the circuit. Inert gas (e.g. SF6) or vacuum are used as dielectric mediums due to the high voltage. What is different is how the breakers are controlled - rather than being its own stand-alone overcurrent protection device as in a home electrical panel, it's just a dumb device controlled by one or more multifunction microprocessor relays that are designed to detect a variety of power system fault conditions and clear them rapidly to avoid damage to expensive equipment.