On the significance of recent EHV transformer failures involving winding resonance

The recent failures of four EHV auto-transformer no load tap changers is interpreted. The failures were a direct and immediate consequence of transmission line faults as far as 340 miles away. The related system transient behavior is analyzed, and the transformer response to these transients is presented on a quantitative basis. It is demonstrated for these transformers that the ANSI standard dielectric surges offer an inadequate test of winding insulation remote from the line terminals where significant winding resonance is known to occur. The extent of these test limitations to other transformers is discussed.

[1]  A. M. Sletten,et al.  Electric Breakdown of Long Gaps in Transformer Oil , 1964 .

[2]  A.J. McElroy,et al.  Experience with part-winding resonance in EHV auto-transformers: Diagnosis and corrective measures , 1975, IEEE Transactions on Power Apparatus and Systems.

[3]  J. W. Kalb,et al.  How the switching-surge family affects line insulation , 1963, Electrical Engineering.

[4]  Harold A. Peterson,et al.  A Dynamic Surge Arrester Model for Use in Power System Transient Studies , 1972 .

[5]  L. V. Bewley,et al.  Traveling Waves on Transmission Systems , 1931, Transactions of the American Institute of Electrical Engineers.

[6]  P. A. Abetti.  Correlation of Forced and Free Oscillations of Coils and Windings , 1959, Transactions of the American Institute of Electrical Engineers. Part III: Power Apparatus and Systems.

[7]  D. F. Shankle,et al.  Field Measurement or Switching Surges as Modified by Unloaded 345-Kv Transformers , 1963 .

[8]  D. F. Shankle,et al.  Field Measurement of Switching Surges on Unterminated 345-Kv Transmisson Lines , 1963 .

[9]  J. Murray Weed,et al.  Abnormal Voltages in Transformers , 1915, Transactions of the American Institute of Electrical Engineers.

[10]  Frank W. Smith,et al.  Staged Tests on the TVA - SCEC 500-kV Interconnection Between Johnsonville and West Memphis , 1967 .

[11]  S. B. Griscom,et al.  The Apple Grove 750-kV Project- Equipment Design and Instrumentation , 1965 .

[12]  L. V. Bewley,et al.  Methods of determining natural frequencies in coils and windings , 1941, Electrical Engineering.