To overcome such challenges, the Italian Transmission System Operator (Terna S.p.A.) developed a new concept of on-line diagnostic system which could highlight malfunctions of its substation equipment (critical power components such as HVDC circuit breakers (DCCB) , current transformers, voltage transformers, surge arresters, power transformers, etc.), before these can cause an outage of the substation. This system combines a number of local sensor devices with an asset management DSS (decision support system) called MBI (Monitoring & Business Intelligence). Goal of the MBI-system asset management tool is better handling maintenance interventions, by fostering the use of standardized condition based maintenance.
As for power transformers, their monitoring has been carried out using commercially available sensors.
Dissolved gases are monitored through a gas-alarm device; temperatures are monitored via Pt100 resistance thermometer probes; currents are measured through the current transformers of the relevant bay (i.e., the set of local equipment whose signals are concentrated together via fiber optic). All signals are directly acquired in 4-20 mA or converted in such format and sent to the peripheral monitoring unit (UM). From the bay concentrator the measures and reports are transmitted to the peripheral system MRE (Electrical Grid Monitoring), if any. Then some warnings and indicators of degradation are transmitted to the Operation & Maintenance Support Platform (PSE) and MBI platforms by using the IEC 60870-5-101 or IEC 60870-5-104 protocols.
The remotization work (controls locally carried out) started in 2011 on transformers in service already equipped with sensors. The real-time parameters of nine transformers are now available on-line in the PSE platform.
The continuous analysis and collection of data will allow to improve the performance of the MBI decision support system as well as to better address the condition-based maintenance of the monitored transformers and, thus on-line diagnostic system.