The effect of humidity on space charge accumulation in XLPE

This paper investigates the effect of different humidity concentration in cross-linked polyethylene (XLPE) material, cut from HV cables, on space charge accumulation, through space charge measurements performed by the pulsed electroacoustic technique. Space charge measurements were carried out in a climatic chamber, at room temperature and humidity concentration from 5 to 95%. Tests were also performed in laboratory environment, with relative humidity close to 40%. Variation of the threshold for space charge accumulation and, in particular, for charge packet formation was detected as a consequence of relative humidity modification. In particular, a reduction of space charge amount and disappearance of charge packets increasing relative humidity concentration was observed at high fields. The results of conduction current measurements support the space charge results, showing significant variation of quasi steady-state charging current.