International Journal of Energy Engineering          
International Journal of Energy Engineering(IJEE)
Frequency: Yearly
Editor-in-Chief: Prof. Sri Bandyopadhyay(Australia)
TNB Experiences Using Dielectric Response Technique to Assess Insulation Condition of High Voltage Current Transformers
Full Paper(PDF, 505KB)
Tenaga Nasional Berhad (TNB) has experienced over 40 cases of high voltage Current Transformers (CT) failures since 2001 to 2011. Post failure analysis indicated that these failures are suspected highly due to deterioration and contamination of the main insulation system. To reduce premature failures and improve the reliability of the asset, TNB has embarked on a trial study on the use of dielectric response technique known as Frequency Dielectric Spectroscopy (FDS) to assess the insulation condition of in-service high voltage CTs. Field measurements were conducted on selected 137 units CT of voltage class 132 kV and 275 kV in TNB Transmission system. Analysis guideline and flow-chart was developed based on typical value of measured parameters for accurate assessment. To reduce premature failures on CTs, strategic decisions were made based on measured CT conditions and its assessment results.
Keywords:Current Transformer; Assessment; Dielectric Response Technique; Analysis Guideline
Author: Gobi Kannan Supramaniam1, Aizam Talib2, P. Eng,C.Eng.1
1.Tenaga Nasional Berhad, Transmission Division, Malaysia
2.TNB Research, Kajang, Malaysia
  1. CIGRÉ Study Committee A3, "State of the Art of Instrument Transformers," Technical Brochure 394, Paris, 2009.
  2. TNB Maintenance Policy, Transmission Division, 2008.
  3. John Lapworth & Richard Heywood, “The Determination of the Dryness of Transformer Insulation: Recent NGC Experience with Polarization Tests,” Proceedings of the International Conference of DOBLE Clients Sec 8-11, 2001.
  4. Tapan Kumar Saha, “Review of Time Domain Polarisation Measurement for Assessing Insulation Condition in Aged Transformer,” IEEE Transaction on Power Delivery, Vol.18, No.4, Oct 2003, pp 1293-1301.
  5. Jorgen Blennow, Chandima Ekanayake, Kzysztof Walezak, Belen Garcia and Stainslaw M.Gubanski, April 2006; IEEE Transaction on Power Delivery Vol 21, No 2: Field Experience with Measurement of Dielectric Response in Frequency Domain for Power Transformer Diagnostics.
  6. Walter S.Zaengl (Swiss Federal Institute of Technology), Nov/Dec 2003; IEEE Electrical Insulation Magazine Vol 19, No.6: Application of Dielectric Spectroscopy in Time and Frequency Domain for HV Power Equipment.
  7. T.Leibfried, A.J.Kachle,D.Pollaro (Siemens AG): Power Transformer Ageing Assessment in Service By Means of The Polarisation and Depolarisation Current (PDC) Analysis.
  8. Maik Koch, Stefan Tenbohlen (University of Stuggart), August 2005; Publication in Tsinghua University, Beijing, China: Diagnostics of Oil-Paper Using Relaxation Current.
  9. Küchler, T.Leibfried, B.Breitenbauch, JJ.Alff, V.Der Houhanessian and W.S Zaengl, Sept 2003; 48th International Colloquium – Illmenau Technical University: Transformer Insulation Diagnosis by Polarization and Depolarization Current Analysis.
  10. Tapan Kumar Saha, October 2003; IEEE Transactions on Power Delivery Vol 18, No. 4: Review of Time Domain Polarisation Measurements for Assessing Insulation Condition in Aged Transformers.
  11. Walter S.Zaengl, “Dielectric spectroscopy in time and frequency domain for HV power equipment,” 12th Intenational Symposium on High Voltage Engineering, Bangalore, India, August 20-24, 2001.
  12. S.M.Gubanski, P.Guinninc, J.Lapworth, P.Werelius, “Dielectric response methods for diagnostics of power transformers,” IEEE Electrical Magazine, Vol. 19, pp 12-18, 2003.
  13. M. Koch, M. Krueger: “A Fast and Reliable Dielectric Diagnostic Method to Determine Moisture in Power Transformers,” International Conference on Condition Monitoring and Diagnosis CMD, Peking, China, 21 - 24 April 2008.
  14. Stephanie Raetzke, Alan McGuigan. “Measuring and Analysing the Dielectric Response of Current Transformer,” OMICRON Product Manual, August 2011, v1.0.
  15. IEC 60422, “Standards Mineral Insulating Oils in electrical equipment- Supervision and maintenance guidance.” pp. 1-78, 2005-10.
  16. IEEE Std62-1995, “IEEE Guide for Diagnostic Field Testing of Electric Apparatus – Part 1: Oil Filled Power Transformers, Regulators, and Reactors”, pp. 5-57, 1995.
  17. OMICRON Application Guide. “Measuring and Analyzing the Dielectric Response of Current Transformer,” August 2011.
  18. S. Raetzke, M. Koch and M. Krueger, “New approach to assess the insulation condition of instrument transformers,” OMICRON Publication, 2011.
  19. CIGRE WG A2.20, Guide on Economics of Transformer Management, pp 21-22, June 2004.
  20. TNB Transmission Condition Monitoring Guideline, 2010.