S-Transform Based Time-Frequency Analysis of Leakage Current Signals of Transmission Line Insulators under Polluted Conditions

  • Natarajan, A. ;
  • Narayanan, Suthanthiravanitha
  • Received : 2014.05.16
  • Accepted : 2014.10.13
  • Published : 2015.03.01


Flashover of power transmission line insulators due to contamination is a major threat to the reliable operation of power system. This paper deals with the analysis of leakage current characteristics of polymeric insulator using S-Transform technique in order to develop a better diagnostic tool to identify the surface condition of outdoor polymeric insulators. In this work, experiments were carried out on 11 kV silicone rubber insulator under AC voltage at different pollution levels. Moving average technique was adopted to find the trend followed by LC peak at different relative humidity conditions. S-Transform was used to find the relationship between energy and frequency content of the leakage current signal with respect to increase in pollution level over a period of time. From the S-Transform time-frequency contour analysis, point of transition to severe arcing due to increase in pollution and its thershold limit were evaluated. Reported results show that the surface condition of insulators could be easily identified from the S-Transform time-frequency analysis of leakage current signals.


Silicone rubber;Insulator;Flashover;S-Transform;Pollution;Time-frequency map


  1. M. Ugur, D.W. Auckland, B.R. Varlow, and Z. Emin, “Neural Networks to Analyze Surface Tracking on Solid Insulators ”, IEEE Trans. Dielectrics and Electr. Insul., vol. 4, no. 6, pp. 763-766, Dec 1997.
  2. S. Chandrasekar, C. Kalaivanan, Andrea Cavallini and Gian Carlo Montanari, “Investigations on Leakage Current and Phase Angle Characteristics of Porcelain and Polymeric Insulator under Contaminated Conditions”, IEEE Trans. Dielectr. Electr. Insul., vol. 16, no. 2, pp. 574-583, Apr. 2009.
  3. I.W.C. Lee and P.K. Dash, “S-Transform Based Intelligent System for Classification of Power Quality Disturbance Signals”, IEEE Trans. Industrial Electronics, vol. 50, no. 4, pp. 800-805, Aug 2003.
  4. S. Mishra, C.N. Bhende and B.K. Panigrahi, “Detection and Classification of Power Quality Disturbances Using S-Transform and Probabilistic Neural Network”, IEEE Trans. on Power Delivery, vol. 23, no. 1, pp. 280-287, Jan 2008.
  5. IEC 60507, Artificial Pollution tests on high voltage insulators to be used on AC systems, 1991.
  6. T.Suda, “Frequency characteristics of leakage current waveforms of an artificially polluted suspension insulator”, IEEE Trans. Dielectrics and Electr. Insul., vol. 8, no. 4, pp. 705-709, Aug 2001.
  7. V. Jayaprakash Narayanan, M. Sivakumar, K. Karpagavani and S. Chandrasekar, “Prediction of Flashover andd Pollution Severity of High Voltage Transmission Line Insulators Using Wavelet Transform and Fuzzy C-Means Approach”, Journal of Electrical Engineering & Technology, vol. 9, no. 5, pp. 1677-1685, 2014.
  8. R. Sarathi, S. Chandrasekar and N. Yoshimura, “Investigations into the Surface Condition of the Silicone Rubber Insulation Material using Multiresolution Signal Decomposition”, IEEE Trans. Power Delivery, vol. 21, pp. 243-252, 2006.
  9. Shihua Zhao, Xingliang Jiang, Zhijing Zhang, Jianlin Hu, And Lichun Shu, “Flashover voltage prediction of composite insulators based on the characteristics of leakage current”, IEEE Trans. Power Delivery, vol. 28, no. 3, pp. 1699-1708, 2013.
  10. R.Sarathi and S.Chandrasekar, “Diagnostic study of the surface condition of the insulation structure using wavelet transform and neural networks”, Electric Power Systems Research, Elsevier, vol. 68, pp. 137-147, 2004.
  11. S. Kumagai, B. Marungsri, H. Shinokubo, R. Matsuoka and N. Yoshimura, “Comparison of Leakage Current and Aging of Silicone Rubbers and Porcelain in both Field and Salt-fog Tests”, IEEE Trans. Dielectrics and Electr. Insul., vol. 13, no. 6, pp. 1286-1302, Dec 2006.
  12. L. H. Meyer, S. H. Jayaram and E. A. Cherney, “Correlation of damage, dry band arcing energy, and temperature in inclined plane testing of silicone rubber for outdoor insulation”, IEEE Trans. Dielectrics and Electr. Insul., vol. 11, no. 3, pp. 424-432, 2004.
  13. Suwarno, “Leakage Current Waveforms of Outdoor Polymeric Insulators and Possibility of Application for Diagnostics of Insulator Conditions”, Journal of Electrical Engineering & Technology, vol. 1, no. 1, pp. 114-119, 2006.
  14. R.S. Gorur, E.A. Cherney and J.T. Burnham, Outdoor Insulators, Ravi S. Gorur Inc Phoenix, Arizona 85044, USA, 1999.
  15. Looms J.S.T., Insulators for high voltages, IEE series, 1990.
  16. S.H. Kim, E.A. Cherney and R. Hackam, “Hydrophobic behaviour of Insulators Coated with RTV Silicone Rubber”, IEEE Trans. on Electr. Insul., vol. 27, no. 3, pp. 610-622, 1992.
  17. G. Montoya, I. Ramirez, J. I. Montoya, “Correlation among ESDD, NSDD and leakage current in distribution insulators”, IEE Proc. of Generation, Transmission and Distribution, vol. 151, no. 3, pp. 334-340, 2004.
  18. A. Cavallini, S. Chandrasekar and G. C. Montanari, “Inferring Ceramic Insulator Pollution by an innovative Approach Resorting to PD Detection”, IEEE Trans. Dielectrics and Electr. Insul., vol. 14, no. 1, pp. 23-29, 2007.
  19. V. Jayaprakash Narayanan, B. Karthik and S. Chandrasekar, “Flashover Prediction of Polymeric Insulators Using PD Signal Time-Frequency Analysis and BPA Neural Network Technique”, Journal of Electrical Engineering & Technology, vol. 9, no. 4, pp. 1375-1384, 2014.
  20. R. S. Gorur and H. M. Schneider, “Surface resistance measurements on non-ceramic insulators”, IEEE Trans. Power Delivery, vol. 16, pp. 801-805, 2001.