Acoustic location of transformer PD under non-ideal conditions

Partial discharge activity in large power transformers being detected during acceptance testing, or with on-site testing triggered by alarming DGA results, must be located as precise as possible to start corrective actions. Here, acoustic location of the activity is a valuable tool and sources offering a direct oil path to the accessible tank wall are usually an easy find at high precision. However, often the location is deeper buried in the winding and, hence, acoustic transmission is hampered by attenuation, reflection, dispersion, and transmission following oil channels, spacer gaps, and other paths. Thus, "textbook solutions", such as solving the sphere functions produce misleading results and understanding the limitations as well as the remaining possibilities of acoustic location is…