Bar-to-bar discharge activity is also a common phenomenon
on high voltage generators. This type of activity
takes place in the end-arm portion of the winding between
two bars. It occurs when the air gap between the
bars is too small to support the electrical stress. This activity
will also cause insulation degradation leaving a white
powder on the surface of the bars, noticeable during visual
inspection. These discharges can occur between bars
from different phases, or between a high voltage and a
neutral-end bar of the same phase. It can also be observed
between bars of the same plane, or at the crossover
of the end-arm between top and bottom bars, as simulated
in our laboratory and illustrated in Figure 7.