To detect PD associated with these various defects, three approaches are possible,
namely chemical, acoustic and electrical detection.
In relation to chemical detection, as indicated above, under PD stressing SF6 will
degrade to produce characteristic byproducts [79]. By gas sampling, it is possible to
detect these and thereby infer the presence and, indeed, the nature of PD activity.
Unfortunately, the technique is not quantitative and its effectiveness can be compromised
by desiccants in the GIS chambers which absorb water – but also these
byproducts.