Feature Analysis of Numerical Calculated Data from Sweep Frequency Analysis (SFRA) Traces Using Self Organizing Maps

This paper presents a comprehensive investigation of the Self Organizing Map (SOM) classification process of good and defective power distribution transformers. Three main features were extracted from the numerical calculation method of the Sweep Frequency Response Analysis (SFRA) signals acquired from the transformers. These features are the input vectors for the SOM classification. Analysis of the results has shown the capability of the features and the SOM classification method to differentiate between good and defective transformers

Comparing Simulation Results and Experimental Measurements of Electroluminescence Phenomenon in Dielectric Materials

Under continuous application of high electrical stresses, the insulation system of an underground power cable is subjected to long-term degradation that can eventually cause premature breakdown of the cable. This is as a result of electronic charges being injected into the dielectric material when intense electric field is applied. These charges will then interact with polymer molecules; causing even more charges to accumulate within the vicinity of the material and thus further deterioration. The interaction of the charges can lead to the dissipation of energy in the form of photons; a process known as electroluminescence (EL). In addition to space charge probing, the measurement of EL has becoming increasingly prominent in understanding the mechanisms that contribute to the early electrical ageing of an insulating material. This paper attempts to simulate EL behaviour based on the underlying hypotheses of charge injection and bipolar recombination processes that take place within a polymer. A detailed comparison between the computation results and the experimental measurements carried out by different researchers will be discussed in order to evaluate the mechanisms responsible for this phenomenon

Feature Analysis Of Numerical Calculated Data From Sweep Frequency Analysis (Sfra) Traces Using Self Organizing Maps

This paper presents a comprehensive investigation of the Self Organizing Map (SOM) classification process of good and defective power distribution transformers. Three main features were extracted from the numerical calculation method of the Sweep Frequency Response Analysis (SFRA) signals acquired from the transformers. These features are the input vectors for the SOM classification. Analysis of the results has shown the capability of the features and the SOM classification method to differentiate between good and defective transformers

Modeling electroluminescence in insulating polymers under ac stress: effect of excitation waveform

A charge transport model allowing the description of electroluminescence in polyethylene films under ac stress is proposed. The fluid model incorporates bipolar charge injection/extraction, transport and recombination. The physics is based on hopping mobility of electronic carriers between traps with an exponential distribution in which trap filling controls the mobility. The computation mesh is very tight close to the electrodes, of the order of 0.4 nm, allowing mapping of the density of positive and negative carriers during sinusoidal, triangular and square 50Hz voltage waveforms. Experiment and simulation fit nicely and the time dependence of the electroluminescence intensity is accounted for by the charge behaviour. Light emission scales with the injection current. It is shown that space charge affects a layer 10 nm away from the electrode where the mobility is increased as compared with the bulk mobility due to the high density of charge. The approach is very encouraging and opens the way to model space charge under time-varying voltages