Inverters that functionally ground the array through an intentional resistance integral to the inverter, shall meet the requirements in a) and c), or b) and c) below:NOTE System designers using resistance between the array and ground that is not integral to the inverter, must consider whether a shock hazard on the array is created or made worse by the addition of the resistance, based on the array design, resistance value, protection against direct contact with the array, etc. Requirements for such considerations are not included here because if the inverter does not provide the resistance, it is neither the cause of, nor capable of protecting against, the hazard.a) The value of the total resistance, including the intentional resistance for array functional grounding, the expected insulation resistance of the array to ground, and the resistance of any other networks connected to ground (for example measurement networks) must not be lower than R = (VMAX PV/30 mA) ohms. The expected insulation resistance of the array to ground shall be calculated based on an array insulation resistance of 40 MΩ per m2, with the surface area of the panels either known, or calculated based on the inverter power rating and the efficiency of the worst-case panels that the inverter is designed to be used with.NOTE Designers should consider adding design margin, based on considerations such as panel aging which will reduce the array insulation resistance over time and any AC component of the leakage current caused by array capacitance to ground. The array insulation resistance measurement in c) below will ensure that total resistance is not too low and the system remains safe, but if the design margin is not adequate, the system will refuse to connect following the array insulation resistance check.