Quick Answer
To ensure proper rating of lightning protection gear, a thorough analysis of the solar array's power and location is required, using relevant standards such as IEC 62305 and UL 1449. This involves calculating the maximum fault current and selecting a lightning arrester with a suitable discharge current rating. Regular maintenance and inspections are also crucial.
Calculating the Maximum Fault Current
The maximum fault current can be calculated using the solar array’s total power and the local electrical grid’s characteristics. For instance, if a 100 kW solar array is connected to a 480 V, 3-phase grid, and the grid’s short-circuit current is 10,000 A, the maximum fault current can be calculated as 100 kW / 480 V = 208 A (per phase) * √3 = 360 A (L-L). This value should be used to select a lightning arrester with a suitable discharge current rating.
Selecting a Suitable Lightning Arrester
According to IEC 62305, the discharge current rating of a lightning arrester should be at least 50% higher than the maximum fault current calculated earlier. For the example above, the discharge current rating of the lightning arrester should be at least 360 A * 1.5 = 540 A. Additionally, the arrester’s voltage rating should match the solar array’s DC voltage (typically up to 1000 V) and its power rating should be sufficient to handle the maximum fault current.
Installation and Maintenance Considerations
Proper installation of the lightning protection gear is crucial to ensure its effectiveness. The lightning arrester should be installed in close proximity to the solar combiner box, and the grounding system should be designed to handle the maximum fault current. Regular inspections and maintenance of the lightning protection gear are also essential to ensure it remains functional and effective in protecting the solar array from lightning strikes.
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