Effects of geomagnetically induced currents in the BC Hydro 500 kV system

Measurements are presented of increased harmonic currents in a 500 kV power system due to geomagnetically induced currents (GIC). The measurements were made of 60 Hz, 120 Hz, and 180 Hz currents and GIC in a 1200 MVA transformer. The recorded increases in the harmonic currents at times of GIC are consistent with computer model calculations made for a transformer operating under conditions of partial saturation. The computer model is used to determine transformer operation for GIC up to 100 A/phase, calculating magnetizing current an reactive power demand as well as the harmonic current levels. An assessment is made of the effect of these parameters on system operation.>