ROTOR HEATING EFFECTS FROM GEOMAGNETIC INDUCED CURRENTS

The heating effects at the end-ring connection areas of the rotor due to the harmonic current generation of a saturating unit transformer fr om geomagnetic induced 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 da mage 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 duri ng strong GIC storms through the use of appropriate negative- sequence current monitoring and alarms.