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Conditional Based Maintenance with Online Partial Discharge Measurements of HV and MV Switchgear Systems R.G.A. Zoetmulder, S. Meijer and J.J. Smit Presented by J.J. Smit Question number 8 Introduction and Goal Insulation test: 1: Detection 2: Defect identification 3: Defect localization 4: Risk assessment Goal: To apply the UHF measuring technique used for High Voltage Switchgear (HV GIS) also for : - Medium Voltage Gas Insulated Systems (MV-GIS) - Medium Voltage Air Insulated Systems (MV-AIS) - Medium Voltage Oil Insulated Systems (MV-OIS) The measuring system * Hard-ware • Broadband detection > UHF (till several GHz) • With this method noises can be suppressed by measuring at a frequency band with a low noise-level Components: 1 a: Internal UHF coupler 1 b: external UHF coupler 2 : Pre-amplifier 3 : Spectrum analyzer 4 : Computer 10 kV Air Insulated Switchgear system-1 - 10 kV Air Insulated - Measuring locations are small inspection windows - Vacuum Circuit-Breaker - UHF signals can propagate through these inspection windows and can than be detected Front-side Back-side Begin stadium (less affected) Advanced stadium (More affected) Surface discharge at one of the phase connectors of the circuit-breaker 10 kV Air Insulated Switchgear system-2 Conclusions Measurements with the external UHF coupler are applicable to medium voltage switchgear installations, e.g. air insulated switchgear, as well as to HV switchgear systems. Using advanced PD analysis techniques distinction can be made between the different patterns detected by the external UHF coupler. UHF PD measurements can contribute to CBM procedures. With UHF PD measurements one can also determine the position of system design errors, which then can be corrected.