It has long been established that PD (partial discharge) activity generally increases with humidity. In dry conditions PD can reduce to levels below detection, whereas, in humid conditions the same equipment will clearly show PD.

Is the apparent change in PD due to a change in the propagation path (PD source to sensor) or a genuine reduction in the actual PD?

Or, to put it another way, does the PD remain constant but become easier to detect in higher humidity conditions?