From the relay protection perspective, there is little doubt that implementing a neutral grounded through a resistor (for example, via a zig-zag transformer) in PV, WTG, or BESS networks is essential for the selective operation of earth-fault protection.

However, I have tried to find clear requirements for this — primarily in IEC and IEEE standards — but without success. Common sense alone is not always sufficient; it is important to justify engineering decisions with references to official documents.

Has anyone encountered this issue and managed to trace it to a standard, or at least to an acceptable practical solution? Or perhaps you have some ideas on this matter?