Diagnosis of insulation conditions : Interpretation of partial discharges from φ-q-n pattern, pulse-sequence and pulse waveform
Appearance of electrical discharges in high voltage apparatuses with reasonable magnitude and frequency can be interpreted as abnormal condition. The discharge may take place in several types. Firstly, corona discharges which represents abnormal electric stress on a conductor. Secondly, void discharge which represents discharge take place in a gas filled void in solid or liquid insulation. Thirdly, treeing discharge which takes place in tree channels inside a solid insulation. This paper reports experimental results on the three kinds of discharges. The analysis was focused on the phi-q-n pattern, the time sequence between consecutive pulses and the waveform of a discharge pulses. The difference among them maybe useful to diagnose of insulation condition.
- [Show abstract] [Hide abstract] ABSTRACT: The problem of identification of partial discharge (PD) phenomena occurring in an insulation system is addressed in this paper. PD distributions coming from different sources, such as internal voids, as well as surface and corona discharges, are compared. In particular, the investigation focuses on the Weibull probability function applied to pulse charge-height distribution. It is shown that the different discharge sources can be identified on the basis of the value of the shape parameter of the Weibull distribution and that identification holds even when two PD sources are combined, i.e. are active simultaneously. In this case, the application of the 5-parameter Weibull function permits separation of PD phenomena, and recognition by means of the shape parameter value associated to each phenomenon. Finally, the proposed procedure is applied to practical objects, i.e. insulation systems of rotating machines, with real insulation defects, showing promising on-field application prospective0Comments 62Citations
- [Show abstract] [Hide abstract] ABSTRACT: The amount of literature on partial discharge (PD) and partial discharge induced degradation is vast. In the past 10-20 years significant progress has been made on research within partial discharge induced aging of dielectrics. Researchers now agree on the main mechanisms pertaining to this topic. With the advent of a new generation of dielectrics of which many properties now can be affected by the introduction of small amounts of nano-sized particles it seems to be a good moment to review the progress on the understanding of PD induced aging. Focusing on internal partial discharge in solid polymeric insulation this paper tries to identify achievements and at the same time challenges still to be solved.0Comments 92Citations
- [Show abstract] [Hide abstract] ABSTRACT: Online partial discharge (PD) testing has become a powerful tool to plan the maintenance of stator windings of high voltage motors and generators. Interpretation of PD data is best done by monitoring the trend in PD over time. Unfortunately the trend in PD is sometimes difficult to ascertain, especially if the humidity within the stator is variable over time. This paper shows several examples of how PD is affected by humidity in operating machines. Laboratory experiments were also performed to duplicate this phenomenon. In most practical situations, it appears that the PD activity decreases as the humidity increases.0Comments 16Citations