Partial discharge characteristics of long-term operated 550kV GCB epoxy spacer

We developed partial discharge current pulse waveform analysis (PD-CPWA) method in order to estimate insulation degradation of solid insulators. Focusing on the time transition of sequential PD pulses from their inception to breakdown (BD), PD-CPWA was applied to epoxy samples cut from an actual 550kV GCB spacer which had been used in a substation for 25 years. PD parameters such as peak value I, rise time tr, di/dt in a single PD current pulse waveform and time interval /spl Delta/t of sequential PD pulses were analyzed. Experimental results revealed that PD generation until BD was not continuous, but disappeared frequently. tr increased drastically and /spl Delta/t shorter than 1 msec appeared at about 0.4 sec before BD, which might be prediction parameters of BD.