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Introduction

In the realm of residential photovoltaic (PV) system design, a recurring debate revolves around the necessity of installing a circuit breaker before the surge protector (SPD) within the PV combiner box. The decision to include or omit a circuit breaker hinges critically on the need for heightened system safety and uninterrupted power supply stability. SPDs serve the primary purpose of absorbing and mitigating voltage surges caused by lightning strikes or other overvoltage phenomena, safeguarding the PV system from potential damage.

The Importance of Circuit Breakers as Backup Protection:

When a voltage limiting SPD, such as Metal-Oxide Varistors (MOV), encounters a substantial current surge or experiences degradation leading to a short-circuit failure, a backup protective device becomes imperative to swiftly disconnect the faulty branch, precluding the risk of fire hazards or further system malfunctions. Installing a circuit breaker ahead of the SPD assumes this critical role effectively.

Firstly, in the event of an SPD short-circuit failure, a properly selected circuit breaker can detect excessive current flow almost instantaneously and promptly sever the circuit, mitigating the threat of a fire outbreak.

Secondly, circuit breakers offer versatility in selection, allowing for different types and ratings to be chosen based on practical needs. This ensures that while catering to the daily operational current requirements, the breaker’s breaking capacity adequately covers the maximum possible short-circuit current at that specific position in the electrical circuit.

However, the choice of circuit breaker is of utmost importance. It must remain unaffected by transient overvoltages under normal operating currents yet react reliably when the SPD fails due to a short circuit. Furthermore, considering the extremely brief duration of a lightning impulse—measured in nanoseconds—a circuit breaker’s contacts would not be significantly affected. Thus, the performance of the breaker remains unimpaired even during the passage of a lightning current.

Solar Combiner Boxes

Conclusion

While it is not an absolute requirement to incorporate a circuit breaker before every PV combiner box’s surge protector, doing so proves highly beneficial and often necessary in many scenarios, particularly in areas prone to lightning strikes or installations demanding elevated safety standards. By incorporating a circuit breaker, the PV system gains an additional layer of defense that ensures swift disconnection of faulty SPDs, thereby enhancing system safety and maintaining power continuity.

With advancements in technology, specialized backup protection devices tailored specifically for SPDs have emerged in the market, offering potentially superior performance. These alternatives are equally worthy of consideration in the quest for optimized system protection. Ultimately, the inclusion of a well-chosen circuit breaker—or alternative backup protection device—prior to the surge protector in a PV combiner box stands as a prudent measure to fortify the resilience and reliability of the overall solar power generation system.