First - understand what partial discharge (PD) is ... and is not. Partial discharge (PD) happens when a small area of insulation in a high voltage environment cannot cope with the electrical stress and breaks down. It doesn't span the whole distance between two insulated electrodes – that's why it's called 'partial'.
So - to ensure something stays "PD free" requires at least one of the following conditions: 1) an insulation with absolutely no imperfections that can well exceed the applied local voltage stress, or 2) a low enough voltage that the existing insulation (with or without imperfections) can withstand the stress.
Note that the severity of partial discharge can also be affected by environmental conditions such as altitude, humidity, presence of (external and/or internal) contaminants, proximity of conductors from different polarities/phases, etc.
Converting energy to motion for more than half a century
Please review my earlier response thoroughly - I DID answer your question.
To design for "PD free" - create an insulation system impervious to dielectric breakdown at any voltage up to the rated voltage of the component, AND create a system that successfully eliminates any material, manufacturing, and environmental effects that may influence the development and/or severity of PD. Oh yes - better also make the system cost-effective to manufacture.
Since there isn't an insulation system out there meeting the "PD free" criteria, you're on your own. Otherwise, you'd be re-inventing the wheel (or perhaps infringing on someone's patent).
The geometry for lead arrangement is pretty self-explanatory: keep appropriate physical spacing between conductors of different phases and/or polarities. How much is appropriate? Depends on the conductor insulation and surrounding medium.
Converting energy to motion for more than half a century
