Tillståndsövervakning av fjärrstyrda distribuerade frånskiljare i mellanspänningsnätet / Condition Monitoring of Remote Controlled Distributed MV DisconnectorsEriksson, William January 2019 (has links)
This thesis studied the possibilities to monitor disconnectors’ operating times to indicate when maintenance needs to be performed. The main hypothesis of this study was that the operational time in a disconnector manoeuvre, open or close, correlates with the resistance in the mechanical components. If the operational time deviates too much from the baseline duration, then this may indicate that the disconnector needs to be maintained. Five substudies were conducted to study if it was possible to monitor the operating time and if the logged operating times had been affected by external conditions. Together they illustrated it might be possible to monitor operating times, but this study cannot state it with certainty based on the available data. From the results, it was possible to see that normal operating times for disconnectors varied within a group of disconnectors of the same type and manufacturer. Why it differed within groups of the same type and manufacturer might be explained by the effects of external conditions. It was shown that a varying transfer time occurred when logging the operation times in the front end processor. Furthermore, the year of production of the disconnector affected the median operating time, but it did not affect the operating time in an intuitive way, that is the operating time did not get longer for older disconnectors. Also, the geographical position of the disconnector may affect the operating time. When these external conditions were considered, disconnectors were concluded necessary to be studied individually. If disconnectors would be studied individually condition monitoring might be possible, although, it is not possible at the moment because of the lack of observations per disconnector.
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