What are the typical maintenance activities you conduct on OLTCs to ensure they function properly and their lifespan is prolonged? OLTC assessments are based on a DRM measurement and internal inspection of the diverter switch inserts. We adopt the appropriate diagnostic procedures depending on the number of OLTC switchings. First, we perform oscillographic measurements (DRM). Next, we set up an internal inspection for the tap-changer head, check the main and auxiliary contacts’ quality and the springs. Finally, we perform oscillographic measurements again to ensure the asset functions correctly. Thanks to these measurements, we can adjust the maintenance scope to increase the lifespan of the OLTC. How much experience do you have with dynamic resistance (DRM) and vibro-acoustic measurements (VAM) on OLTCs? We have performed oscillographic measurements for 20 years. In addition to that, we have been conducting OLTC vibro-acoustic measurements for a year now. We often used our MT3 device for this type of measurement. For some years now, we have only been using OMICRON measuring devices, and the recent addition of OLTC vibro-acoustics and our cooperation with OMICRON has enhanced our experience. What are the benefits and limitations of these methods? Measurements are the first step in assessing the technical condition of the on-load tap changer. The benefit of this is that it provides a quick and cost-effective initial assessment of the asset’s condition. However, correctly evaluating the on-load tap changer is only possible after the condition of the contacts and the OLTCs’ mechanism have undergone internal inspection and visual checks. What stages of the maintenance cycle do you apply these methods to, and how do you interpret and analyze the results? Typically, they are performed before and after maintenance work, but sometimes, they can be performed more frequently between inspection intervals and electrical measurements. We then compare our results with our customers’ standards, norms, similar switches, and experience. Does measuring OLTCs help facilitate the maintenance and maintenance schedule of the unit? Absolutely. OLTC measurements help predict the operation time and repairs for the tap changer, while the online vibro-acoustic measurement is a quick method for initial tap-changer diagnostics. These methods provide a quick and cost-effective initial assessment of the OLTCs’ condition, which can help prevent costly downtime and repairs in the future. In some cases, Diverter Switch Insert (DSI) defects can be diagnosed earlier between transformer inspections, and vibro-acoustics can help assess the OLTCs’ technical condition much earlier without taking the transformer out of service and conducting a costly inspection. If the method and analysis of the results are refined, online vibro-acoustic measurements offer excellent opportunities for scheduling the OLTC for maintenance in the future. Thanks for the interview. 8
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