Partial discharge early warning system in gas-insulated switchgear

Electrical, in particular VHF and UHF, and acoustical PD detection have shown to be very sensitive tools for on-line monitoring. To meet the requirements of after installation testing and diagnostics, a sensitivity of 5 pC has to be guaranteed. In particular, for proper diagnostics the signal attenuation has to be taken into account In practice, different GIS components, such as circuit breakers, disconnectors have an influence on the propagation of the VHF/UHF PD signals. Investigations show that the location of sensors can be optimized in order to obtain ensured sensitivity for the complete installation. For on-line purposes easy for use diagnosis support is needed. Thereto key-values of PD frequency spectrum are defined which are continuously analyzed during normal operation of the GIS in order to set-up an early-warning system for long term life-time management of gas-insulated material. Advanced PD analysis is applied to make a distinction between regular and irregular conditions of the insulation system. In this way statements are possible regarding the risk of an occurring defect for the lifetime performance.