Transfer functions for UHF partial discharge signals in GIS

The principles of electromagnetic radiation by partial discharges (PD) in gas insulated substations (GIS) are described. Calculated transfer functions are presented, showing that transverse electric modes are predominant for radial PD currents in the coaxial geometry. By using actual PD current pulses from a free moving particle together with the measured sensitivity of a UHF coupler, the entire transfer function for the PD detection problem is modelled. The relationship between UHF signal energy at the coupler output and the electronic component of the PD pulse is investigated using the model, revealing a significant degree of correlation.