Utvärdering av riskbaserat underhåll för transformatorer via CNAIM-modellen : En analys av olje- och gasanalys påverkan på hälsobedömningen av transformatorer

Sammanfattning

Transformers play a vital and critical role in the electricity grid and their performance and condition is essential for maintaining high quality of supply to the network. Within Ellevio’s maintenance operation there is oil and gas analysis conducted periodically in order to assess the condition of transformers. However, the resources for these analyses involve both in-house efforts and third-party laboratory testing making them a high operational cost. The ability to implement risk based maintenance utilizing existing network and asset data would enable a more cost-effective maintenance planning. The goal of this study is to implement and evaluate the Common Network Indices Methodology (CNAIM) model for condition based maintenance of transformers. CNAIM can be used to evaluate a Health Score, Probability of Failure and Consequence of Failure for an electrical componenet. In order to do this one specific station and transformer were chosen. This was done since the same station has recently installed sensors that measure the same parameters as the manual oil and gas analysis. One of the goals of this study was to also compare the costs of manual testing versus sensor measurements and through this come up with a recommendation for new maintenance intervals for transformers. Conclusions of this study are that it is possible to implement the CNAIM-model but with some assumptions regarding the chosen transformer component. The main limitations arose from the fact that the studied transformer was not an established component in the CNAIM-package. The results of the study show that with the CNAIM-model a transformers Health Score, Probability of Failure and Consequence of Failure can be evaluated. The conclusion regarding a recommendation for new maintenance intervals integrated both manual testing and sensor measurements.