The standard IEC61730 requires a lightning impulse test with the standard 1.2/50 µs impulse and the test must be within tolerances when the solar panel is connected.
This requires the impulse generator to operate across a wide load range of solar panel sizes. The physical dimensions and construction give a capacitance from 10 to 200 nF.
The MIG1203SOLAR instrument has been designed with seven ranges to enable solar panels from 30 cm to 2.5 m to be tested.