In order to understand the influence of partial discharge types on sensitivity of UHF sensing method

the floating type partial discharge was produced with a testing model

and detected via HF amplifiers in three frequency bands of 10～80 MHz

150～250 MHz and 300～800 MHz. The discharge gap was set at 0.2

0.8 and 1.4 mm

respectively. With the increasing discharge gap

the PD quantity increased

however the amplitude of the PD signals detected in 300～800 MHz frequency band decreased. This result indicates that the UHF PD signals can not be used to assess the severity of a PD effectively. It is suggested to make the assessment based on the relative amplitudes of the signals from different frequency bands.