The difference between a DC isolator switch and a DC circuit breaker

DC (Direct Current) isolator switches and DC circuit breakers are two important components in solar PV systems. Although they may look similar and both serve to disconnect the circuit, they have different functions and purposes. In this article, CHYT will elaborate on the differences between a DC isolator switch and a DC circuit breaker.

DC Isolator Switch

As its name implies, a DC isolator switch is designed to disconnect DC power in a solar PV system. It serves as a safety device that isolates the DC circuit from the rest of the system, making it safe to work on. The main function of a DC isolator switch is to provide disconnection and isolation of the power source. It is usually installed outside of the inverter, such as on the roof, and can be manually switched on or off.

A DC isolator switch typically has a high breaking capacity, which means it can handle high voltage and current levels without malfunctioning. This is crucial in case of a DC arc fault, where the switch needs to be able to withstand the high energy release and prevent further damage to the system. In addition, a DC isolator switch is designed to be weatherproof and durable, making it able to withstand various environmental conditions.

DC Circuit Breaker

Unlike a DC isolator switch, a DC circuit breaker is designed to protect the circuit from overload and short circuit currents. It acts as a switch that automatically trips when the current exceeds its limit, preventing any further current flow that can cause damage to the system or pose a safety hazard. A DC circuit breaker is usually installed within the inverter, or in a fused combiner box.

A DC circuit breaker has a lower breaking capacity compared to a DC isolator switch, since it is mainly designed to prevent damage caused by overcurrent and short circuits rather than disconnection and isolation of the power source. It also has a lower voltage capacity, typically in the range of 80-600V DC, depending on the rated current. In addition, a DC circuit breaker is more sensitive to temperature changes, and may require periodic maintenance to ensure proper function.

Conclusion

In summary, a DC isolator switch is a disconnection device designed to isolate the DC power source from the rest of the system, while a DC circuit breaker is a protection device designed to prevent damage caused by overcurrent and short circuits. Both devices are critical in ensuring the safety and proper function of a solar PV system, and should be selected and installed according to their respective functions and rated capacity.