Power transformers, a key element of the electrical grid, are subjected to different levels of electrical, thermal, mechanical, and chemical stress during service. To ensure reliable and safe operation, it is key to assess the continuously aging insulation of the system during a transformer’s life cycle.
Partial discharge (PD) measurements are a highly effective, non-destructive tool for the measurement, assessment, and localization of weak spots in complex insulation systems.
In our Paper of the Month, OMICRON application engineer Udo Ranninger und asset expert Michael Krüger, present a detailed case study based on their experience performing PD measurement, localization and monitoring on a 300 MVA oil-filled transformer. The transformer had been in service before, but was moved to a new substation. The tests were performed after on-site installation to ensure proper re-filling of the horizontal-oriented bushings.
The authors demonstrate in this article how electrical PD measurements and trending can be more sensitive and instantaneous compared to the analysis of dissolved gases in oil. Analysis of the PD signals and performing acoustical PD localization can provide operators with valuable information when it comes to defect localization, interpretation and risk assessment.