Experience with Impact of GIC on Noise Performance of Large Power Transformers

Two large 3-phase 345 / 115 kV Autotransformers of the same design, located at two different locations in the Northeast region of USA, have been experiencing occasional high sound level excursions of short duration. Detailed analysis performed over several months has found a high degree of correlation between these sound level excursions and magnitudes of the Geomagnetically Induced Current (GIC) flowing into the windings of these transformers. This paper presents detailed measurements and analysis performed by the authors. Results obtained, and the conclusions reached, in regard to the nature of the relationship between transformer noise and magnitudes & signature of the GIC are also included.