Geomagnetic Disturbances (GMD) Impacts on Protection Systems

This report discusses the impacts of Geomagnetic Disturbance (GMD) phenomena on protection systems. GMDs create low frequency primary currents which circulate between the transmission lines, high-side Y-grounded transformers and the ground. GMD events may cause unanticipated damage to high voltage equipment such as transformer, generator, shunt capacitor and SVC, and may have significant impacts on radio or satellite communications. GMD events may also impact the performance of protection and control systems, depending on the severity of the GMD in the area. The low frequency (quasi-DC) current created by GMD events is referred to as the Geomagnetically Induced Current (GIC). GIC may cause elevated levels of harmonics. GIC flow in Y-grounded transformers may cause high magnetic flux which could cause severe damage through overheating.