Influence of the structure dimension of GIS on the partial discharge

Partial discharge (PD) monitoring plays an important role in the online maintenance of the gas insulated switchgear (GIS). In recent years, the ultra high frequency (UHF) method for PD detection arouses great interest of many researchers because of the high sensitivity and anti-interference capability. The coupling of UHF signal is the key to the detection of partial discharge in GIS. The structure size of GIS has great impacts on the PD signal, because the cutoff frequency of the high order mode of the electromagnetic (EM) wave depends on the diameters of the inner conductor and enclosure. In this paper, the influence of the inner conductor diameter is investigated by varying the center conductor size. The inner coupler is adopted to receive the partial discharge signal, and two types of PD sources are tested in the experiment. Firstly, the amplitude and the duration of the time domain signal and the frequency spectrum are focused, and their variations with the size of inner conductor are analyzed. Besides that, In order to research the changes of the TEM mode component and the high order mode component, low pass (LP), band pass (BP) and high pass (HP) filters are applied to process the PD signals, and the cumulative energy rates are calculated to indicate the energy distribution. In addition, a simulation using the FDTD method is conducted for comparison with the experimental results, and it indicates that the results of experiment and simulation are almost consistent.