Permanent PD monitoring for generators: Smart alarm management

Permanent Partial Discharge Monitoring (PDM) systems were installed in several generators in South America in the last 2 years, in the framework of a long term project aimed at monitoring a large number of machines placed in different powerplants. All PDM units send automatically data and alarms to a Central Unit (CU) placed in the Utility´s headquarter. The Partial Discharge (PD) detectors installed in each machine are characterized by an Ultra Wide Bandwidth (UWB), thus they are able to record the entire waveform of PD pulses. Separation on line of multiple sources is done through the Time-Frequency (TF) map. After multiple source separation, it is possible to tune proper alarm logics for each PD phenomenon without being affected by on-line noise and disturbances. In addition, different criteria can be used to evaluate the trend of PD phenomena depending on PD source nature, e.g., if they are relevant to microvoids, slot, stress grading, bar to bar, delamination or corona. Eventually, multiple PD activities occurring in the same phase can be dealt with separately, avoiding false alarms coming from the sum of the statistical parameters relevant of each PD source.