This white paper presents an overview of the state of the science in methodologies and approaches to predicting and reducing the impact of geomagnetic disturbances (GMDs) on the electric grid. It starts by presenting the background and context of the issue and concludes with the identification of the related open research areas.

What Is a Geomagnetic Disturbance?
A geomagnetic disturbance (GMD) begins as a large solar flare on the surface of the sun. The resulting ejection of charged particles can impact earth and create rapid changes in the configuration of Earth’s magnetic field—called a geomagnetic disturbance (GMD). These GMDs induce slowly varying electric fields at the Earth’s surface that cause currents, known as Geomagnetically Induced Currents (GICs), to flow on man-made conducting paths such as transmission lines. From an electric grid perspective, the most important GIC impacts are to the power transformers connected to these transmission lines. The GICs can result in transformer damage and disruption of the proper operation of the electric grid through increased harmonic generation and reactive power consumption. In the rare extreme, a large GMD could have the potential to simultaneously damage a significant number of transformers on the bulk transmission system and to interrupt electric service for many customers for extended periods. Given the high impact, but low probability of such an event, typical risk mitigation strategies are difficult to apply and there is a need for a well-researched risk assessment and mitigation methodology...(go to EPRI download page...)