Time domain PD-detection vs. dielectric spectroscopy

A theoretically developed relationship between partial discharges and the response from a system for dielectric spectroscopy was experimentally confirmed. The losses caused by the discharges were highest at test voltages with low frequencies. At 0.1 Hz, tan/spl delta/ tip-up at discharge inception was very difficult to observe. A very clear tip-up could be seen by detection of the third harmonic in the current through the test object. This is much more sensitive to the detection of internal partial discharges than traditional loss measurements, in particular when using low frequency test voltages.