Geomagnetically induced currents: present knowledge and future research

The knowledge base regarding the production of geomagnetically induced currents (GIC) in power systems is briefly reviewed. The relationship between electric and magnetic fields for a layered earth is derived and used to calculate the electric fields produced in Quebec during the March 13, 1989, magnetic disturbance. Factors influencing the distribution of GIC throughout a system are also examined. The transfer functions of the earth and of power systems vary with frequency and so the relation between GIC and magnetic field variations is most appropriately examined in the frequency domain. Data collection requirements to allow this in future research are discussed