Wet Leakage and Insulation Test on String Level Through IEC 61215

This study explores the adaptation of the IEC 61215 wet leakage and insulation resistance test to the string level in photovoltaic (PV) systems. Traditionally, insulation tests are conducted at the module level, but scaling up to large PV installations with interconnected strings presents new challenges. A mathematical model was developed to calculate the equivalent resistance of strings, considering the parallel connection of modules. Simulations involving 5 million strings of 30 modules were conducted, and new pass/fail criteria were defined based on failure thresholds and confidence limits. These criteria enable early detection of insulation failures, with three distinct zones—pass, uncertainty, and failure—established to provide a robust framework for evaluating insulation at the string level. Results show that string-level testing offers a more comprehensive assessment of insulation integrity, improving reliability and reducing testing time in large installations. Future work will involve validating the model through further field trials and experimental measurements under various conditions.