ADVANCED PARTIAL DISCHARGE DIAGNOSTICS AS EARLY WARNING SYSTEM TO RECOGNISE DEFECTS IN GAS-INSULATED SWITCHGEAR (GIS)

摘要

Since the early seventies SF6 gas insulated substationsrn(GIS) are in operation all over the world. As stated inrninternational CIGRé reports, GIS’s have proven to bernvery reliable. Therefore, GIS in all voltage ranges arernused at important nodes in the grid. However, a totalrnabsence of unexpected discontinuity in the operationrncannot be excluded. The main outage costs, althoughrndifficult to quantify, can be very high due to repair andrnmaintenance costs and costs of non-delivery. Thereforernthe detection, localisation and recognition of thoserninsulation defects at an early stage is of great importancernfor maintenance purposes.rnMost of these defects show partial discharge (PD) activityrnsome time before failure. Electrical, in particular VHFrnand UHF, and acoustical PD detection have shown to bernvery sensitive tools for on-line monitoring. Recently forrnon-site measurements a sensitivity check has beenrnproposed by CIGRé WG 15.03, which can be used torndetermine on-site the minimum sensitivity of thernmeasuring method. To meet the requirements of afterrnlaying testing and diagnostics, a sensitivity of 5 pC hasrnto be guaranteed. In particular, for proper diagnostics thernsignal attenuation has to be taken into account. Inrnpractice, different GIS components, such as circuitrnbreakers and disconnectors have influence on thernpropagation of the VHF/UHF PD signals.rnLaboratory investigations as well as field experiences inrnthe Netherlands are reported, in which PD patternrnanalysis is applied to make a distinction between regularrnand irregular conditions of the insulation system. In thisrnway statements can be done regarding the risk of anrnoccurring defect for an insulation failure.For on-line purposes easy for use diagnosis support isrnneeded. Thereto PD frequency spectrum are analysedrnduring normal operation of the GIS in order to set-up anrnearly-warning system for to prevent failures of gasinsulatedrnmaterial.rnField experiences in 150 kV and 420 kV GIS substationsrnin the Netherlands have proven the sensitivity of such PDrndiagnostics. The method is ready for implementation inrnthe maintenance process.