Uninterruptible power supply systems for railway with predictive diagnostic against power transformer failure

The paper addresses the problem of predictive diagnostic in uninterruptible power supply systems (UPS) for railway. A new UPS for railway applications is proposed. A FMECA (Failure Mode, Effects and Criticality Analysis) analysis carried out on it shows that key issues for the system reliability are the faults occurring in the 3-phase high power transformers and in the battery modules used for energy storage. While at state of art several works address the battery failure problem, for power transformers in known works only thermal and electrical faults are monitored. As a new feature vs. state of art to achieve predictive diagnostic of power transformer fault this work proposes a new electronic instrumentation allowing also for vibration-based mechanical stress diagnosis. Mechanical degradation is tracked through multi-channel vibration measures with sensitivity down to 0.5 mg and signal processing in the transformed frequency domain up to 1 kHz. Experimental measurements on real UPS for railway confirm the validity of the approach.