Influence of tertiary stabilizing windings on zero-sequence performance of three-phase three-legged YNynd transformers. Part II: Tank overheating hazard and short-circuit duty

Abstract This paper analyzes the influence of stabilizing windings in three-phase three-legged YNynd transformers on tank overheating hazard and on the short-circuit performance of such transformers in the event of unbalanced conditions involving zero-sequence currents as asymmetrical faults. It complements a previous companion paper that presented experimental zero-sequence measurements and equivalent circuit calculations for three power transformers. Those previously calculated zero-sequence equivalent circuit parameters are used here to evaluate the comparative performance of YNynd power transformers when the delta stabilizing winding is closed and when it is open. Additionally, it analyzes the effects of other variables, such as relative position of the stabilizing winding, presence of magnetic shunts in the tank walls, and system grounding.

[1]  X. M. Lopez-Fernandez,et al.  Transformer Tertiary Stabilizing Windings. Part I: Apparent power rating , 2012, 2012 XXth International Conference on Electrical Machines.

[2]  J. Peters.  Harmonics in transformer magnetizing currents , 1915, Proceedings of the American Institute of Electrical Engineers.

[3]  O. T. Farry.  Tertiary Windings in Autotransformers , 1961, Transactions of the American Institute of Electrical Engineers. Part III: Power Apparatus and Systems.

[4]  A. Munar,et al.  Zero phase sequence impedance and tank heating model for three phase three leg core type power transformers coupling magnetic field and electric circuit equations in a finite element software , 1995 .

[5]  R. M. Charley,et al.  Recent progress in large transformers , 1931 .

[6]  J. Mini,et al.  Performance of auto transformers with tertiaries under short-circuit conditions , 1923, Journal of the American Institute of Electrical Engineers.

[7]  B. A. Cogbill.  Are Stabilizing Windings Necessary in All Y-Connected Transformers? , 1959, Transactions of the American Institute of Electrical Engineers. Part III: Power Apparatus and Systems.

[8]  King E. Gould.  Instability in Transformer Banks , 1927, Transactions of the American Institute of Electrical Engineers.

[9]  Angel Ramos,et al.  Influence of tertiary stabilizing windings on zero-sequence performance of three-phase three-legged YNynd transformers. Part I: Equivalent circuit models , 2017 .

[10]  Patricia Penabad-Duran,et al.  Transformer Tertiary Stabilizing Windings. Part II: Overheating hazard on tank walls , 2012, 2012 XXth International Conference on Electrical Machines.

[11]  M. E. Skinner,et al.  Transformers for Interconnecting High-Voltage Transmission Systems For Feeding Synchronous Condensers from a Tertiary Winding , 1921, Transactions of the American Institute of Electrical Engineers.

[12]  A. Boyajian.  Inversion Currents and Voltages in Auto-Transformers , 1930, Transactions of the American Institute of Electrical Engineers.

[13]  Lloyd N. Robinson.  Phenomena accompanying transmission with some types of star transformer connections — II , 1917, Proceedings of the American Institute of Electrical Engineers.