Identification of PD sources in solids

It is of great importance not only to detect but also to localise and identify the source of partial discharges (PD). If the PD source type can be identified, it is possible to give a more reliable estimate of the potential damage. The authors present some general arguments for the acoustic mode density in cavities of different dimensionality: flat, hole or spherical. This knowledge may be utilised to identify the shape and size of a discharging cavity in solid insulators using the acoustic technique