The paper examines the development of partial discharge(PD)in gas-insulated switchgear(GIS)due to insulator gap defects.It analyzes the evolution of ultra-high frequency(UHF)PD signals through φ-u scatter plots and φ-n spectrograms at different stages and introduces nine characteristic parameters.The study reveals consistent discharge occurrence patterns during negative and positive half-cycles.Findings show that the frequency and magnitude of discharges during positive and negative half-cycles follow a consistent pattern.Maximum discharge pulse amplitudes and cumulative discharge volumes display exponential growth

while the average intervals between adjacent PD pulses decrease exponentially.Notably

the time intervals between pulses during negative half-cycles consistently exceed those in positive half-cycles

diminishing this difference as PD progresses.The maximum time intervals between discharges also decrease over time.The study provides insights into the physical mechanisms driving these observed changes

correlating them with the microphysical processes of PD evolution.