Recurrent Plot Analysis Of Leakage Current For Evaluating And Monitoring Outdoor Insulator Performance

Generally, the flashover accidents of outdoor insulators can cause serious influence on the operation stability of power system and its equipments. Therefore, it is significant to evaluate and monitor the insulator performance for the prevention of the flashover accidents and the improvement of the power system reliability. In this paper, based on the present investigation of leakage current for evaluating and monitoring outdoor insulators, the recurrent plot technique is proposed to analyze the characteristics of leakage current through the artificial contamination experiments. In accordance with dynamic behaviors and flashover process on the insulator surface, the results obtained aim to investigate the effective methods for performance evaluation and flashover protection of outdoor insulators.In order to determine whether the leakage current during the flashover process has chaotic characteristics, the experiments simulating the insulator flashover in heavy fog were carried out and the chaotic analysis method of time series was selected to analyze the non-linear properties of leakage current in accordance with the flashover process. Lyapunov exponent, fractal dimension, power spectral density, chaos attractor, as well as Poincare map were calculated to reveal that the variation of leakage current during the flashover process has chaotic characteristics. The results demonstrate the feasibility of using the recurrent plot technique for the non-linear characteristic analysis of leakage current.Based on the corresponding relationship between the leakage current and the flashover process in heavy-fog conditions, the wavelet transform technique was applied to decompose the leakage current into different frequency components. The temporal series of the extracted components are extended to m-dimensional phase space by using a phase-space reconstructed method. The recurrent plot is obtained to show that the topological structure of the high-frequency components is prominent to identify non-linear properties of discharge activities. The dynamic behaviors on the insulator surface are graphically illustrated on the rectangular block structures with higher density of points. Based on the analysis of the high-frequency components, the quantitative indicators of recurrent plot are obtained to reflect the underlying mechanism of flashover process. The results obtained indicate that the recurrent plot technique is helpful to improve the accuracy of insulator evaluation. Considering the effect of wet-contaminated environment on the insulator performance, the artificial contamination experiments were conducted to investigate the performance evaluation in multi-environmental factors including contamination degree, ambient temperature and relative humidity. The characteristics of leakage current were extracted to reflect dynamic behaviors on the insulator surface. Based on the limitation of the present analysis method, the topological structure and quantitative indicator of recurrent plot of the leakage current were obtained to reflect the influence mechanism of environmental factors on the outdoor insulation. The recurrent plot method was established for the relationship between the leakage current and the insulator performance.Finally, the phenomena of the rime flashover were observed and the non-linear characteristics of leakage current were analyzed. The experiments are helpful to monitor and reveal the process and mechanism of insulator flashover in rime conditions. The results show that the recurrent plot of leakage current can qualitatively reveal the discharge characteristics during the rime flashover process, and the further quantitative analysis enhances the monitoring and the understanding of the flashover mechanism.In conclusion, the recurrent plot technique gives a visible monitoring method for outdoor insulators to monitor the flashover process and evaluate the operating performance. The topological structure of recurrent plot and its quantification indicators can effectively represent the surface performance and further reveal the characteristics and state transition of surface discharges during the flashover process. Therefore, the recurrent plot analysis of leakage current is an effective method for the insulator monitoring system.