Quartzelec, a leading independent engineering service provider with an ever‑extending global reach, offers permanent online partial discharge monitoring for high voltage (HV) generators and motors, adding to their existing offline monitoring service.

Partial discharge (PD) testing has become a standard diagnostic test, performed on HV electrical machines. There is, however, a difference between online PD monitoring and offline PD testing. Both are valuable diagnostic tools, but only online monitoring provides a real picture of the stator winding condition.

Only when the machine is online can the stresses of the operational environment be achieved:

  • The temperature is high
  • Each stator bar sees different voltage depending on its location in the stator phase
  • The stator bars vibrate under the influence of electromagnetic and mechanical forces

When the machine is offline:

  • The temperature is low (usually ambient)
  • Each stator bar sees the same voltage during the test
  • The stator bars are not subject to electromagnetic and mechanical forces, so they do not vibrate

With online PD monitoring, Quartzelec believe that the risk of stator winding failure can be vastly reduced and this, coupled with other monitoring devices that can be added to the same PDA II analyser package, helps achieve an excellent overall picture of generator stator and rotor health.

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