The selection of suitable solar array fuse requires a comprehensive consideration from four dimensions: system protection requirements, electrical parameter matching, environmental adaptability and safety standards. Specific steps and principles are as follows:
I. Clarify Protection Requirements
Determine the need for fuses:
Single or low parallel: Fuses may be omitted if the rated current of the connection is sufficient (usually more than 1.5 times the short-circuit circuit current of the module) and the fault current does not exceed the safe range of the module or cable.
Multiple parallel strings (≥3 strings): Fuses must be installed. A short circuit in any module can lead to reverse currents flowing into other strings, which can lead to overheating or fire risks.
Locate Protection Locations
Serial protection: Fuses are installed at the positive and negative output terminals of each cell string to prevent a single string fault from affecting the system.
Combiner box protection: protect each parallel branch in the combination box to reduce the fault propagation range.
II. Matching Electrical Parameters
Rated current (%)
Calculation basis: The rated current of the fuse must include the maximum working current of the system and have a certain safety factor.
Effective maximum operating current (Total short-circuit current) x safety factor (generally 1.25 -1.56).
Selection principle: Fuse rating current should ≥ its calculated value, but ≤ the maximum fuse current loaded on the component nameplate (to avoid component damage).
If the calculated value is close to the nameplate value, a closer specification is preferred to avoid excessive derating.
Voltage rating: Fuse rating must ≥ 1000 V or 1500V systems to ensure reliable operation at high voltage.
Disconnection capacity: The disconnection capacity of a fuse (ability to interrupt current during a short circuit) must be greater than the maximum short-circuit current that may occur in the system to prevent secondary failure caused by an arc.
III. Environmental and installation considerations:
Temperature adaptability: Fuse rating current is based on ambient temperature of 25°C. If the actual temperature is higher (e.g., outdoor rooftop), a high-temperature tolerance model or an increase in rated current (10 to 15 per cent for every 20°C increase in rated current) should be selected.
In a low temperature environment (e.g., northern winters), low temperature start-up performance needs to be verified to avoid embrittlement or delay in operation of the fuse due to low temperature. Protective rating: For outdoor facilities, fuses of IP65 or higher should be selected to prevent dust and moisture from getting in and causing insulation to fail.
UV-resistant shell material to extend service life.
Installation Method: DC special: Solar system uses DC power, so it is necessary to choose DC fuse (DC arc is difficult to extinguish, AC fuse is not suitable).
Quick connection: Priority is given to fuses with pluggable terminals for maintenance and replacement.
