Future Trends in Transformer Online Monitoring

The application of online monitoring systems has been intensified over the past two decades and they are now frequently installed with new transformers or retrofitted to the existing ones. A lack of standardization, different asset management strategies and practices between utilities, as well as certain economic factors resulted in systems made to the user’s specifications having different level of complexity: from basic units which monitor only a few parameters, to more comprehensive systems that are monitoring a wide range of parameters and are delivering various diagnostic information related to the transformer’s health. Nowadays data from monitoring systems is in most cases available only in the substation, where data is shown using a locally installed computer, or directly on monitoring devices installed on the transformer where the user can analyze the status of the transformer unit. This makes use of the data impractical and thus prevents the value of the systems to be utilized for a fleet wide asset management. In this paper, future trends in the transformer online monitoring will be presented, based on the previous development of such systems, and according to the concept of the condition-based maintenance of power transformers. As a key functionality, the status of the power transformer will be presented using either a numeric or graphical representation, which will represent the general status of the equipment (health index). This will give the user guidance on how to rank transformers in their network, in order to decide on the schedule and to pinpoint the transformer component which needs to be maintained. For this purpose, the system will need to consider other available information such as results from off-line diagnostic tests, transformer design data and history of known faults. Such approach will enable asset management strategy where the user can implement condition-based maintenance, which will lead to the cost reduction and improvement of reliability and safety with regard to power transformers.