The heating affects at the end-ring connection areas of the rotor due to the harmonic current generation of a saturating unit transformer from geomagnetic induces currents (GIC) on the transmission system have been calculated from observed data and from EMTP studies sponsored by the Electric Power Research Institute. These calculations show that damage may occur during strong GIC storm activity. This damage can occur from unit transformer saturation or other transformers in the system near the generator. The possibility of damage should be monitored during strong GIC storms through the use of appropriate negative-sequence current monitoring and alarms. >