A pole-mounted circuit breaker is a high-voltage switching device specifically installed on overhead utility poles and plays a vital role in protection and control within modern power distribution networks. As an outdoor high-voltage apparatus, it typically employs vacuum interruption technology, featuring a compact structure, high breaking capacity, long electrical life, and requires little to no maintenance. The core function of a pole-mounted circuit breaker is automatic fault isolation. When a serious fault such as a phase-to-phase short circuit or a single-phase ground fault occurs on the line, the breaker can quickly detect the large fault current and automatically trip within tens of milliseconds, accurately isolating the fault point. This prevents a fault on one line from causing an upstream substation to trip and resulting in a widespread blackout. In addition, the breaker is capable of load switching, allowing remote or local operation under normal conditions to connect or disconnect load current for routine maintenance or changes in system operation. Notably, when equipped with a Feeder Terminal Unit (FTU), the pole-mounted circuit breaker enables distribution automation, providing "telemetering, telesignaling, and telecontrol" functions. This allows the dispatch center to monitor line status in real time and remotely control the opening and closing of the breaker. Furthermore, its automatic reclosing feature, following a trip caused by transient faults such as lightning strikes or tree branch contact, automatically attempts to restore power; if the fault has cleared, the breaker re-energizes the line, greatly improving power supply reliability. In practical applications, pole-mounted circuit breakers are widely used as sectionalizing switches on 10kV or 20kV overhead distribution lines, dividing long lines into multiple sections. When a fault occurs in one section, only that section's breaker trips, ensuring continuous power supply to the healthy sections. They are also commonly installed at the point of connection between a customer (such as a factory or residential complex) and the main line, acting as a "watchdog." In the event of a fault within the customer's premises, the breaker automatically trips, preventing the fault from affecting the main line's operation. In summary, the pole-mounted circuit breaker is a key device supporting the construction of smart distribution grids, reducing the duration and scope of power outages, and improving overall power supply reliability.