Event Day Time OP Number of re-ignitions umax (ûL1–E) uext (kV) hh:mm:ss L1 L2 L3 L1 L2 L3 L1 L2 L3 1 1 10:42:26 open 0 0 0 1.85 0.91 1.02 –44.2 21.8 –24.4 2 1 19:53:07 close 13 21 8 2.11 1.18 2.12 –51.4 –28.7 –51.7 3 3 05:03:49 open 0 0 0 1.83 0.89 1.02 –44.2 21.5 –24.6 4 3 13:52:17 close 10 21 0 1.81 1.21 1.39 –44.0 –29.5 –33.8 5 5 06:03:53 open 0 0 0 0.91 1.02 1.83 21.8 –24.4 –43.9 6 5 14:55:56 close 14 20 8 1.32 1.12 1.18 –32.0 27.3 –28.7 Transient recordings and their evaluation parameters damping to minimize reflections, thereby reducing measurement errors. Selecting the right measuring system Measuring transient voltage and current signals requires a sophisticated transient recorder capable of capturing all fast-front transient events. Such a device should record at least two million voltage and current measurement points per second and phase. Since it’s located directly in the substation’s switching bay, it must also operate reliably and accurately 24/7 under harsh climate and EMC conditions. Additionally, it has to provide suitable interfaces for experts to analyze measurement data. Ideally, they should have remote access to measurement results and relevant information that’s easy to extract. Generating reports Time-frequency signals need to be analyzed using advanced tools such as wavelet transformation in order to create meaningful and easily interpretable reports. This analysis condenses relevant data; for instance, it extracts and presents the number of reignitions, the time intervals between them, and the maximum amplitudes of over-voltage occurrences in a wellstructured and easy-to-read report. A three-phase analysis is performed on all signals to determine if the circuit breaker pole is related to electrical stresses. Furthermore, the long-term behavior of the electrical stresses and the VCBs switching behavior (prestrike and re-ignition performance) are evaluated to detect potential changes over time. This allows assumptions to be made about the VCBs long-term performance and suitability for the application under investigation. Successful project implementation One of these projects was made possible by our collaboration with 50Hertz Transmission GmbH in Germany. Typical closing operation with pre-strikes in all phases. 0 100 90 80 70 60 50 t (ms) 40 30 20 10 u (kV) 30 20 10 0 –10 –20 –30 L1 L2 L3 26
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