Why Creepage and Partial Discharge Still Occur After High-Voltage Module Potting: Full Filling Does Not Equal Reliable Insulation

Even fully potted high-voltage modules may suffer creepage, partial discharge or even dielectric breakdown. Adhesive coverage alone does not guarantee a continuous, defect-free insulation path inside the assembly. Air gaps at pin roots, electric field concentration at sharp edges, interfacial delamination, residual contamination and insufficient effective insulation distance after potting can all initiate high-voltage failures. For 800 V and higher voltage platforms, potting reliability shall not be judged merely by whether the cavity is fully filled. Instead, evaluation should focus on the electric field distribution and insulation path formed between high-voltage potential points. 1. Distinguish Breakdown, Creepage and Partial Discharge First: Dielectric breakdown means the insulation medium loses its insulating capability. Under strong electric fields, a conductive channel forms within the originally insulating region, which may directly cause a short circuit between high voltage and low voltage. Second: Creepage refers to conductive paths developing along insulation surfaces. Moisture, contamination and ionic residues raise the creepage risk. Even if high-voltage terminals are covered by adhesive, unstable surface or interfacial conditions do not eliminate creepage hazards. Third: Partial discharge takes place locally within the insulation system. It may not trigger immediate complete breakdown. Nevertheless, repeated discharge over time progressively erodes local insulation and eventually leads to severe electrical failure. In short: No short circuit does not mean the insulation system is free from degradation. 2. Why Tiny Internal Voids Matter Greatly for High-Voltage Potting For high-voltage potting, the primary hazard is not limited to large bubbles visible to the naked eye. More risky defects often include: These locations form a discontinuous structure: solid insulation – air – solid insulation. Electric field redistribution occurs accordingly. The real goal of high-voltage potting is continuous insulation, rather than a visually full appearance. 3. Why Pin Tips and Sharp Corners on Busbars Are High-Risk Zones Electric…