Monitoring of Dielectric Losses and Use of Ferrofluids for Bushing Cooling

At present, the tendency to implement the conditionbased maintenance (CBM), which allows the optimization of the expenses for equipment monitoring, is more and more evident; also, the transformer substations with remote monitoring are increasingly used. This paper reviews all the advantages of the on-line monitoring and presents an equipment for on-line monitoring of bushings, which is the own contribution of specialists who are the authors of this paper. The paper presents a study of the temperature field, using the finite element method. For carrying out this study, the 3D modelling of the above mentioned bushing was performed. The analysis study is done taking into account the extreme thermal stresses, focusing at the level of the first cooling wing section of the ceramic insulator. This fact enables to justify the tanδ variation in time, depending on the transformer loading and the environmental conditions. With a view to reducing the variation of dielectric losses in bushing insulation, the use of ferrofuids instead of mineral oils is proposed.

Authors:

• S. D. Nedelcut
• V. Proca
• D. M. Purcaru

Keywords:

• Monitoring
• dielectric losses
• ferrofluids
• bushing.

References:

[1] Arshad M., Islam S.M., Power transformer condition monitoring and
assessment for strategic benefits, Curtin University of Technology
Department of Electrical & Computer Engineering, Perth, Australia.
[2] Nedelcuţ D., Popa D., Monitoring, Control and Protection Equipment for
Power Transformers, Workshop "Technic Qualification and Transient
Behaviour of Components of High Voltage Substation", Karlsruhe-
Germania, 2002.
[3] Nedelcuţ D., Marinescu A., Sacerdoţianu D., Pâtru I., Purcaru I.,
Equipment for HV Capacitor-Type Bushings (DPD) monitoring, ÔÇ×The
7th International Conference on Live Maintenance - ICOLIM - 2004",
Bucureşti, România, 2004.
[4] Nedelcuţ D., Bicâ M., Ţâlu M., Monitoring of Capacitor-Type Bushings
Considerations Regarding the Influence on Thermal Field Distribution
on Dielectric Losses, IASTED Conference - Power and Energy Systems
EuroPES 2005, Benalmadena, Spain.
[5] Nedelcuţ D., Marinescu A., Sacerdoţianu D., Pâtru I., Purcaru I. -
Equipment for on-line monitoring of capacitor-type bushings, CIGRE
Working Group D1.02 Meeting, Romania, Eforie,2005.
[6] Roth, A., Hochspannungstechnik, IV edition, Wien, 1959.
[7] Wang N., Lu F.C., Li H.M., Analytical Processing of On-Line
Monitored Dissipation Factor Based on Morphological Filter, IEEE,
2004.
[8] Ifrim A., Notinger P., Electrotechnical Materials, EDP, Bucureşti, 1979.
[9] Kuchler A., Neumann C., Koch N., Loppach K., Krause C., Alff J.J.,
Condition Assessment of Aged Transformer Bushing Insulations,
CIGRE 2006.
[10] Bica, M., Thermotechnics and heat engines, Universitaria Publishing
House, Craiova, 2000.
[11] Zalewcki, J., Izolacja przekladnikov pradowych na napiecia 220 i 400
kV, PET (1962), no 7, pages 273-281.
[12] *** Cosmos M.2.6. User guide, Structural Research and Analysis
Corporation, Los Angeles, California, 2000.
[13] *** SolidWorks. User guide, Structural Research and Analysis
Corporation, Los Angeles, California, 2004.
[14] Arnim Nethe, Thomas Scholz, Hanns-Dietrich Stahlmann, Ferrofluid
driven electric motors - heat budget and experimental verification,
Workshop for ferrofluids, Benediktbeuern, 2000.
[15] M.Timko, P.Kopcansky, K.Marton, L.Tomco, Dielectric properties of
magnetic fluid, Institute of Experimental Physics Slovak Academy of
Sciences- Kosice, Faculty of Electrical Engineering and Informatics -
Kosice, Faculty of Aviation - Kosice.