Introduction
Photovoltaic systems introduce unique electrical protection challenges compared to conventional AC installations. DC arc faults are harder to extinguish than AC faults, and string currents can be superimposed in unexpected ways.
Key Selection Criteria
1. DC Voltage Rating
PV systems may operate at 1000V DC or 1500V DC. Always select breakers rated at or above the maximum open-circuit system voltage (Voc at lowest temperature).
2. DC Current Rating
The breaker must handle the maximum short-circuit current (Isc) of all paralleled strings. Apply a safety factor of 1.25 as per IEC 62548.
3. Breaking Capacity
DC arc energy is higher than equivalent AC. Ensure the breaker's DC breaking capacity exceeds the prospective fault current at the installation point.
4. Trip Curve
For solar string protection, B-curve or dedicated PV fuses are typically preferred to avoid nuisance tripping from morning ramp-up currents.
Conclusion
Always consult product datasheets and IEC 62548 / IEC 60364-7-712 when designing protection for PV systems. Cnsoltree application engineers are available to assist with system-specific selection.
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