Drying transformer cellulose insulation by means of synthetic ester

The article concerns the drying of power transformer cellulose insulation by means of synthetic ester. The introduction describes the negative influence of cellulose insulation moisture on transformer operation reliability. It presents the operation limitations resulting from high water content in cellulose insulation. The article presents currently applied methods of drying of cellulose insulation and a new proposed method which makes possible effective and safe water reduction in the transformer. This method consists in replacing mineral oil by synthetic ester during the drying time of cellulose. This electro-insulating liquid is being more widely applied as liquid insulation in transformers mainly due to its fire safety properties and biodegradability. Synthetic ester is characterized by high water solubility, which was used by the author of this article to dry cellulose insulation. The article presents the research results which confirmed the possibility of using synthetic ester for effective drying of cellulose insulation. The author compared the effectiveness of cellulose insulation drying by means of synthetic ester and mineral oil.

[1]  R. Jeffries.  25—THE SORPTION OF WATER BY CELLULOSE AND EIGHT OTHER TEXTILE POLYMERS , 1960 .

[2]  B. García,et al.  Assessing the Use of Natural Esters for Transformer Field Drying , 2014, IEEE Transactions on Power Delivery.

[3]  P. Przybylek,et al.  Water saturation limit of insulating liquids and hygroscopicity of cellulose in aspect of moisture determination in oil-paper insulation , 2016, IEEE Transactions on Dielectrics and Electrical Insulation.

[4]  T. Prevost,et al.  Water Absorption of Cellulosic Insulating Materials used in Power Transformers , 2007, 2007 IEEE International Conference on Solid Dielectrics.

[5]  Z. Nadolny,et al.  Bubble effect as a consequence of dielectric losses in cellulose insulation , 2010, IEEE Transactions on Dielectrics and Electrical Insulation.

[6]  S. R. Lindgren,et al.  Bubble evolution from transformer overload , 2001, 2001 IEEE/PES Transmission and Distribution Conference and Exposition. Developing New Perspectives (Cat. No.01CH37294).

[7]  H. Borsi,et al.  Initiation and formation of partial discharges in mineral-based insulating oil , 1994 .

[8]  H. Borsi,et al.  Drying of transformer insulation using zeolite , 2004, IEEE Electrical Insulation Magazine.

[9]  Grzegorz Dombek,et al.  Thermal properties of a mixture of mineral oil and synthetic ester in terms of its application in the transformer , 2016, 2016 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP).

[10]  Hossein Borsi,et al.  A new method for drying the paper insulation of power transformers during service , 2000, Conference Record of the 2000 IEEE International Symposium on Electrical Insulation (Cat. No.00CH37075).

[11]  A. Graczkowski,et al.  Moisture in cellulose insulation of power transformers - statistics , 2013, IEEE Transactions on Dielectrics and Electrical Insulation.

[12]  I. Fofana,et al.  Water in Oil-Filled, High-Voltage Equipment, Part I: States, Solubility, and Equilibrium in Insulating Materials , 2007, IEEE Electrical Insulation Magazine.

[13]  Piotr Przybylek.  A comparison of bubble evolution temperature in aramid and cellulose paper , 2013, 2013 IEEE International Conference on Solid Dielectrics (ICSD).

[15]  K. Rapp,et al.  Transformer insulation dry out as a result of retrofilling with natural ester fluid , 2012, PES T&D 2012.

[16]  Oleg Roizman,et al.  Moisture equilibrium and moisture migration within transformer insulation systems , 2008 .

[17]  I. Fofana,et al.  Water in oil-filled high-voltage equipment part II: water content as physicochemical tools for insulation condition diagnostic , 2007, IEEE Electrical Insulation Magazine.

[18]  B. Garcia,et al.  A review of moisture diffusion coefficients in transformer solid insulation - Part 2: Experimental validation of the coefficients , 2013, IEEE Electrical Insulation Magazine.

[19]  Hanna Moscicka-Grzesiak,et al.  The influence of water content and ageing degree of paper insulation on its mechanical strength , 2010, 2010 10th IEEE International Conference on Solid Dielectrics.

[20]  J. C. Burgos,et al.  Diffusion coefficient in transformer pressboard insulation part 2: mineral oil impregnated , 2014, IEEE Transactions on Dielectrics and Electrical Insulation.

[21]  A. W. Stannett,et al.  A review of paper aging in power transformers , 1985 .

[22]  T. Leibfried,et al.  The electrical strength of transformer oil in a transformerboard-oil system during moisture non-equilibrium , 2003, 2003 Annual Report Conference on Electrical Insulation and Dielectric Phenomena.