As the core protection component on the DC side of a PV system, 1500V PV fuses primarily face three types of failures: failure to blow, poor contact, and incorrect selection. The following is a fault analysis and solution based on operational and maintenance practices:
1. Fuse Failure
Symptom: After the fuse blows, the resistance becomes infinite, causing the string to short-circuit.
Cause:
Overload or Short Circuit: The string current exceeds the fuse rating (e.g., a 15A fuse carrying 20A current), or there is a short circuit on the DC side (e.g., a direct connection between the positive and negative terminals of a module).
Installation Error: The phase and neutral wires are swapped during wiring, causing the lightning protection module to break down and the fuse to blow.
Environmental Factors: Insufficient fuse derating in high-temperature environments, or prolonged exposure to humidity can degrade insulation performance.
Solution:
Troubleshooting Overload/Short Circuit:
Use a multimeter to measure the open-circuit voltage of the string. If the voltage is abnormal (e.g., below 350V or above 650V), check the module connections and bypass diodes. Check the DC switch, terminal blocks, and cable connectors for looseness or damage.
Replacing the fuse:
Select a fuse with a matching rated current (e.g., if the maximum string current is 12A, select a 15A fuse).
Preferably, use a model with temperature compensation (derating by 20% is recommended for high-temperature environments).
Proper installation:
Strictly distinguish between the phase and neutral wires during wiring and avoid swapping them.
Use specialized tools to crimp the fuse terminals, ensuring the contact resistance is ≤ 0.35mΩ.
II. Poor Contact
Symptom: Overheating of the fuse contacts, string current fluctuations, or intermittent shorting.
Cause:
Lack of firm terminal crimping: The fuse and connector are not tightly crimped, resulting in increased contact resistance.
Oxidation corrosion: Long-term exposure to humidity or salt spray can cause oxidation on the terminal surface.
Vbration loosening: Bracket vibration increases the gap between the fuse and connector.
Solution:
Tightening the terminals:
Use a torque wrench to tighten the fuse terminals to a standard torque (e.g., 2.5N·m). Check the terminal temperature regularly. If it exceeds 85°C, re-crimp.
Corrosion Protection:
Apply conductive paste to the terminals to reduce contact resistance.
Use stainless steel or tinned copper terminals for improved corrosion resistance.
Vibration Reduction Measures:
Install rubber pads at the connection between the bracket and the fuse to reduce vibration.
Regularly check the bracket mounting bolts to prevent loosening.
III. Faults with Incorrect Selection
Symptom: The fuse frequently blows or fails to protect the system.
Cause:
Rated current mismatch: Failure to consider factors such as ambient temperature and irradiance fluctuations during fuse selection can cause the fuse to blow under normal current.
Insufficient breaking capacity: The fuse is not selected based on the system's maximum short-circuit current (e.g., a 1500V system requires a breaking capacity of ≥50kA).
Fault current.
