Typically, in a quiet factory-type environment, discharges in a large power transformer
can be located to within a volume the size of a football within a couple of hours
and to within the size of a fist within a working day. That said, there is some variation
in the estimated success rate using this technique according to manufacturer. Some
claim total success whereas others are more circumspect admitting that they would
be unlikely to detect a source, using this technique, embedded deep in a winding.