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Problem with electrical fault in UPS installation

Dear Pololu masters,
I have found this topic by making and analysis of a electrical fault happened in one installation. Basically, there are two main UPS providing redundant supply to equipment by using STS, each STS input connected to each UPS.
The maintenance staff explained that:

  • one UPS capacitors output stage were found destructed after the fault, EVEN the output fuses.
  • The STSs made switchover but somehow, there was a lack of supply to consumers provoking, in some cases shutdowns (equipments with single PS) or destruction of one PS in equipment with redundant PS.
    After checking your interesting article, which I found looking for articles explaining what happens in events like:
  • transient output in UPS if their output capacitors explode
  • transient output in UPS after shortcircuit of their output
  • possible damage in UPS in the event of shortcircuits in the output
  • output in the output in UPS if their input absorbs a mains perturbance
    I wonder if you can give me your opinion about:
  • may a shortcircuit in the output of the UPS could cause destruction of their capacitors, in the cause the fault was caused by a shortcircuit in the output (this hypothesis because the FUSES were found fused)
  • if the capacitors exploded by an unkwown origin rise of voltage or temperature, but not caused by the shortcircuit in the output, why downwards the STSs made switchover and even consumer equipment had damage in their PS
    thanks in advance by any idea or hint could be given
    best regards