Analysis of the results of on-line Partial Discharge Monitoring and the impact of the maintenance actions on a 30 MVA synchronous generator

Power utilities are lately investing in asset management systems and tools that provide them with analytical parameters from field data to properly evaluate the conditions of their electrical assets, in particular the ones connected into the generation and transmission networks. Any fault leading to an outage could result in huge monetary losses related not only to repair costs but also to lack of energy generation or availability. This is particularly true in the case of electrical assets such as power generators like the one hereafter described and analyzed. One of the tools available for the asset managers to perform such evaluation is the on-line monitoring of the Partial Discharge (PD) phenomena, a non-intrusive technique capable of evaluating in real-time the conditions of the electrical insulation system, commonly considered the weakest point of most electrical assets and the principal source of faults leading to electrical outages. In this paper, an example of the effectiveness in the usage of such technique is discussed about a 30 MVA synchronous generator. Data related to the PD phenomena detected in the insulation system are reported together with the relevant analysis and their behavior over monitoring sessions. Moreover, since during the monitoring period some maintenance actions have been carried out by the utility owning the power station, the relation with the detected PD phenomena will be shown and discussed. This allows performing some critical evaluation about the effectiveness of the maintenance actions carried out.