Core Functions of Solar PV String Fuses
Solar photovoltaic (PV) string fuses is an important protection device on the DC side of PV system. Its core functions are:
Overload and Short-Circuit Protection: When a PV string overflows due to an internal fault (such as module damage or short circuit) or external factors (such as an adverse current caused by sun shade), the fuse fuses the circuit to prevent overheating, damage or even fire.
Multi-Level Protection Coordination:
In PV systems, fuses usually work together with protective devices in equipment such as combiner boxes and inverters to form multi-level protection systems. Serial fuzes, for example, can quickly isolate fault branches, prevent faults from spreading throughout the array, and ensure the proper functioning of other parts of the system.
Equipment Safety Isolation: After melting, there will be obvious breakpoints, easy to operate and maintenance personnel to carry out safety maintenance. At the same time, it prevents faulty currents from flowing back to other healthy strings or battery storage systems, reducing the risk of secondary damage.
Compared with conventional fuses, photovoltaic applications have unique requirements:
Due to its DC characteristics, high voltage environment and outdoor application conditions, PV systems have the following special requirements for fuses:
DC Arc Extinguishing Capability:
Zero crossover challenge: DC power supply lacks periodic zero crossover points, making arc extinguishing far more difficult than AC power. Photovoltaic fuses must be specially designed (e.g. elongating arc or using arc extinguishing materials such as quartz sand) to force arc extinguishing and to prevent continuous combustion that could lead to fire.
High rupture capacity: Fuses shall be capable of withstanding high DC voltage (e.g. 1000V, 1500V) and large short-circuit circuit currents from PV systems. Broken capacity is generally required above 20kA to ensure reliable fault isolation.
Environmental Adaptability:
Weatherability: Outdoor facilities must withstand high temperatures (e.g., desert areas), low temperatures (e.g. high latitudes), UV radiation and variations in humidity. The casing material must possess anti-aging and anti-corrosion properties.
Protection rating: IP65 or higher is required to prevent dust and rainwater from getting in and causing insulation to fail.
Precise parameter matching:
Rated Voltage: Maximum DC voltage must be ≥ system (e.g., a 1500V system requires a a 1500V or higher fuse) to prevent arc reignition during disconnection.
Rated current: The maximum working current of the string (taking into account short-circuit current Isc, temperature coefficient and number of parallel runs) shall be multiplied by the safety factor (usually 1.25-1.56) and shall not exceed the rated current of the protected component.
Time current characteristics: System protection requirements must be met, for example, by fusing at 1.35 times the rated current within an hour to ensure a rapid fault response while avoiding false tripping.
