Resistance To Tracking Of Polymer Materials And Nolinear Analysis

Tracking failure is a dielectric breakdown phenomena occurring on polymer surfaces comprising carbonized conductive path, resulting in a permanent loss of the surface dielectric performance. Because the resulting comparative tracking index (CTI) has wide variation, an attempt has been made to evaluate the resistance to tracking more consistently. Numerous studies have been conducted to characterize the properties of discharge currents by calculating the discharge quantity or analyzing the power spectrum. However, discharge is a complicated process and reproducible results of the indices mentioned above are difficult to obtain. Studying the non-linear characteristics of the discharge current can assist in understanding the underlying mechanism of the process because: 1)the surface discharge process is complex and irregular; 2) after the power frequency is filtered, the platform outlines of the discharge waveform as first discussed by Mandelbrot. In this paper, recurrence plots (RPs), recurrence quantification analysis (RQA), fractal dimensions, largest Lyapunov exponent, chaos attractors and Poincarémaps, which can provide quantitative, qualitative, visualization description of statistics characteristic of the discharge current in m-phase space, are reconstructed or calculated to extract information from the discharge currents.It is found that the largest Lyapunov exponent of the discharge is positive, the fractal dimensions as a function of embedding dimension will saturate at a value, the recurrence plots shows the chaotic frame-work patterns, and the he Poincarémaps will have the chaotic characteristics. The results show that the discharge currents of the tracking test do exhibit chaotic behavior.Due to the widespread use of polymeric insulating materials in radiation environments, there is an increasing demand to evaluate the radiation effects on the surface dielectric characteristics of polymeric insulating materials. The resistance to tracking of polymer materials can be changed by gamma-ray radiation through altering the molecular structure. Because the radiation has complex effect on the molecular structure of polymer materials through mechanism like chain scission, cross-linking and oxidation, it is hard to demonstrate the effect on resistance to tracking. This paper presents the recurrence plot (RP) and recurrence quantification analysis (RQA) approaches to analyze the surface discharge of gamma-ray irradiated polymeric insulating materials based on the tracking test described in IEC60112. Recurrence plots of the discharge currents are derived. It is found that the resistance to tracking could be projected on a map as a function of the dosage of irradiation. The recurrence plots and recurrence quantification analysis are sensitive and give visual and quantitative methods for identification of the dosage of irradiation effects on the resistance to tracking.In order to satisfy the safety of fireproofing, the flame retardants are used in almost all polymer insulating materials. Although the flame retardant can hinder the fire from spreading, it may have negative influence on the electrical insulation. However, the research about the effect of flame retardant on the electrical insulation is very few. Consequently it is important to investigate the influence of the flame retardant on the dielectric strength. In order to assess the performance of the insulation degradation, the non-linear analysis methods are adopted in this research. The recurrence plot topological structures and fractal dimensions are studied. It has been shown that the methods are valid. For varied discharging stages, the attractors of discharge current show different characteristics in evolutionary tracks, the topological structure and grain direction of recurrence plots show significant differences, and the fractal dimensions of discharge current change obviously.