Auto-recloser and medium-voltage circuit-breakers are key equipment for ensuring the stable operation of power lines. They can quickly detect and interrupt harmful fault currents, thereby preventing faults from escalating and improving power supply reliability. Although their functions overlap, they differ significantly in design principles and application scenarios. The following sections will systematically explain their differences from various perspectives.

Different Market Environments

Internationally, reclosers are extensively utilized in overhead power lines. In contrast, China has adopted an approach based on pole-mounted circuit breakers (medium-voltage circuit breakers) combined with FTUs, establishing a clear separation between primary and secondary equipment. Over time, this model has progressively evolved toward a deeper integration of primary and secondary systems. It is noteworthy that reclosers, which are widely used abroad, have already achieved a high level of primary-secondary integration.

Moreover, differing development paths have influenced product design. China’s power industry initially depended largely on imported technology, before transitioning toward independent R&D. This has led to the formation of a circuit breaker product system with distinct domestic characteristics. On the other hand, internationally renowned recloser manufacturers generally possess independent design capabilities, resulting in products that exhibit stronger brand identity and greater independence in both appearance and functionality.

Different Product Compositions

Reclosers are typically equipped with a controller by default, as they cannot function properly without one. In contrast, circuit breakers mostly employ spring mechanisms, which allow them to be combined with manual operating mechanisms and overcurrent coils.

Therefore, fundamentally, reclosers represent an integrated form of primary and secondary equipment, whereas circuit breakers and FTUs (Feeder Terminal Units) are two relatively independent product categories.

Different voltage sensors

Whereas early pole-mounted circuit breakers typically did not incorporate voltage sensors, reclosers were equipped with six as standard.

Different implementation standards

Reclosers and circuit breakers adhere to different implementation standards: reclosers are designed according to IEC 62271-111 (C37.60), while circuit breakers follow IEC 62271-100. These differences in standards result in numerous variations in parameter settings and type testing procedures.

The most critical distinction lies in the type testing phase: during short-circuit tripping tests, a recloser operates entirely under the control of its own integrated controller, without relying on external substation signals. This means that, unlike circuit breakers—which depend on external tripping signals and lack self-protection capabilities—reclosers are equipped with independent self-protection functionality.

Different operating mechanisms

Generally, reclosers use permanent magnet mechanisms, while circuit breakers use spring mechanisms.

Different Reclosing Sequences and Logic

Reclosers typically support fast reclosing sequences, such as “O-0.5s-CO-2s-CO-2s-CO,” achieving a “four-open, three-close” operation. In contrast, circuit breakers generally only support slow reclosing sequences, such as “O-0.3s-CO-180s-CO.”

The main functional difference lies in the software design of their controllers. Although both are protection devices, the controllers of European and American reclosers and domestic FTUs (Feeder Terminal Units) have increasingly diverged in their technological development, leading to significant differences in their software functions.

The reclosing logic of reclosers is derived from extensive long-term research by multiple international manufacturers. To accommodate diverse customer requirements, this logic is open and highly configurable—for instance, multiple protection parameters can be set for each opening operation (e.g., initial trip: instantaneous 600A, inverse time overcurrent 200A, etc.).

In comparison, the reclosing logic and protection parameters of FTUs are primarily customized according to the requirements of the domestic power grid, with limited openness. Their internal logic operates like a black box: most parameters and logic are fixed in the underlying code, and any modifications require adjustments at the program level. This type of software architecture is quite common within the domestic industry.

Different Communication Functions

DNP 3.0 is widely used abroad but less commonly adopted in China. This protocol requires an open configuration that allows users to customize point tables. Moreover, the system must be fully adaptable to user needs, which leads to a significant development workload. However, Strong Power can use the DNP3.0 communication protocol.