Partial discharge: overview and signal generation

It is shown how a partial discharge (PD) within a test sample generates a signal that can be measured outside the apparatus under test. Because the transfer function between the phenomenon within the apparatus under test and the signal that can be measured can vary widely, measured partial-discharge magnitudes rarely have absolute meaning and are often referred to as effective partial-discharge magnitude to acknowledge this uncertainty. The most common sources of PD are floating components, corona, and voids. Each of these is considered in turn, and the fundamentals of how the phenomenon generates a current in the external circuit are explained.>