Investigating the Transformer Operating Conditions for Evaluating the Dielectric Response

Authors: Jalal M. Abdallah

Abstract:

This paper presents an experimental investigation of transformer dielectric response and solid insulation water content. The dielectric response was carried out on the base of Hybrid Frequency Dielectric Spectroscopy and Polarization Current measurements method (FDS &PC). The calculation of the water content in paper is based on the water content in oil and the obtained equilibrium curves. A reference measurements were performed at equilibrium conditions for water content in oil and paper of transformer at different stable temperatures (25, 50, 60 and 70°C) to prepare references to evaluate the insulation behavior at the not equilibrium conditions. Some measurements performed at the different simulated normal working modes of transformer operation at the same temperature where the equilibrium conditions. The obtained results show that when transformer temperature is mach more than the its ambient temperature, the transformer temperature decreases immediately after disconnecting the transformer from the network and this temperature reduction influences the transformer insulation condition in the measuring process. In addition to the oil temperature at the near places to the sensors, the temperature uniformity in transformer which can be changed by a big change in the load of transformer before the measuring time will influence the result. The investigations have shown that the extremely influence of the time between disconnecting the transformer and beginning the measurements on the results. And the online monitoring for water content in paper measurements, on the basis of the oil water content on line monitoring and the obtained equilibrium curves. The measurements where performed continuously and for about 50 days without any disconnection in the prepared the adiabatic room.

Keywords: Conductivity, Moisture, Temperature, Oil-paperinsulation, Online monitoring, Water content in oil.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1075559

References:

[1] P. J. Griffin and J. Christie, "Effects of Water and Benzotriazole on Electrostatics Charge Generation in Mineral Oil/Cellulose Systems", Proceedings: Static Electrification in Power Transformers, EPRI TR- 102480, Project 1499-99, June 1993.
[2] O. Rouse, "Mineral Insulating Oil in Transformers", Electrical Insulation Magazine, Vol. 14, No. 3, pp. 6-16, May/June 1998.
[3] V. G. Arakelian, I. Fofana "Water in Oil-Filled High-Voltage Equipment Part II: Water Content as Physicochemical Tools for Insulation Condition Diagnostic", IEEE Trans. Dielectr. Electr. Insul.Vol. 23, No. 5, September/October 2007.
[4] IEEE Guide for Loading Mineral-Oil Immersed Power Transformers, IEEE Standard C57.91, Institute of Electrical and Electronic Engineers, New York NY, 1995.
[5] A. Setayeshmehr, J.Abdallah, A. Akbari, H. Borsi and E. Gockenbach, "Evaluation of water exchange between oil and paper in transformer under operating condition ", the 16th International Symposium on High Voltage Engineering Johannesburg ,ISH 2009.
[6] Y. Du, M. Zahn, B.C. Lesieutre and A.V. Mamishev and S.R. Lindgren "Moisture Equilibrium in Transformer paper-oil systems", IEEE Electr. Insul. Mag., Vol. 15, No. 1, 1999.
[7] T. K. Saha, "Review of Modern Diagnostic Techniques for Assessing Insulation Condition in Aged Transformers", IEEE Trans. Dielectr. Electr. Insul. Vol. 10, pp. 903-917, 2003.
[8] W.S. Zaengl, "Dielectric Spectroscopy in Time and Frequency Domain for HV Power Equipment, Part I: Theoretical Considerations", IEEE Elec. Insul Mag., Vol. 19, No. 5, pp. 5-19, 2003.
[9] W.S. Zaengl, "Application of Dielectric Spectroscopy in Time and Frequency Domain for HV Power Equipment", IEEE Elec. Insul. Mag., Vol. 19, No. 6, pp. 9-22, 2003.
[10] "Relative Humidity," Britannica Online1994-1997 Encyclopedia Britannica, Inc, URL: http://www.britannica.com/.
[11] Y. Du, A. V. Mamishev, B. C. Lesieutre, M. Zahn, and S. H. Kang, "Moisture solubility for differently conditioned transformer oils," IEEE Trans. Dielect. Elect. Insulation, vol. 8, pp. 805-811, Oct. 2001.
[12] B. Garcia, J. C. Burgos, "A Moisture-in-Oil Model for Power Transformer Monitoring- Part I: Theorical Foundation", IEEE Trans. Power Delivery. Vol. 20, NO. 2, pp. 1417-1422, 2005.
[13] B. Pahlavanpour, M. Martins, D. Eklund, "Study of moisture equilibrium in oil-paper system with temperature variation", 7th International Conference on Properties and Application of Dielectric Materials, Nagoya, Japan, 2003.
[14] P. J. Griffin, " Water in Transformers-so what!" in National Grid Condition Monitoring Conf., May 1996.
[15] A. Seytashmehr, I. Fofana, C. Eichler, A. Akbari, H. Borsi and E. Gockenbach, "Dielectric Spectroscopic Measurements on Transformer Oil- paper Insulation under Controlled Laboratory Conditions", IEEE Trans. on Diel and Elec. Insul. Vol. 15, pp. 1100-1111, 2008.
[16] T. K. Saha and P. Purkait, "Effects of Temperature on Time-Domain Dielectric Diagnostics of Transformers", Australasian Universities Power Engineering Conf., Christchurch, New Zealand, 2003.
[17] S. Zaengl, "Dielectric Spectroscopy in Time and Frequency Domain for HV Power Equipment, Part I: Theoretical Considerations", IEEE Elec. Insul Magazine, Vol. 19 No. 5, pp. 5-19 September/ October 2003.
[18] A. B. Supatra, "The Latest On-Site Non-Destructive Technique for Insulation Analysis of Electrical Power Apparatus", Weidmann-ACTI Annual Technical Conference, Sacramento, USA, 2004.
[19] A. Setayeshmehr, C. Eichler, A. Akbari, H. Borsi and E. Gockenbach, "Condition Evaluation of Oil-Pressboard Insulation by Fourier Transform Of Time Domain Dielectric Response", NORDIS 2007.
[20] A. Akbari, A. Setayeshmehr, M. Farahani, H. Borsi and E. Gockenbach, "A Software Technique for Transforming Dielectric Data from Time Domain to Frequency Domain for Insulation Diagnosis of Power Transformers", 15th International Symposium on High-Voltage Engineering (ISH), Ljubljana, Slovenia, 2007.
[21] H. Borsi, E. Gockenbach, M. Krueger, "Method and Device for Measuring a Dielectric Response of an Electrical Insulation System", European Patent EP 1729139.
[22] M. Koch, M. Krueger, "A Fast and Reliable Dielectric Diagnostic Method to Determine Moisture in Power Transformers" International Conference on Condition Monitoring and Diagnosis, Beijing, China, April, 2008.
[23] U. Gafvert, G. Frimpong, and J. Fuhr: "Modelling of dielectric measurements on power transformers", Proc. 37th Session "Large High Voltage Electric Systems" (CIGRE), paper 103, Paris, France, 1998