Reduction of geomagnetically induced current impacts by optimized neutral point connections

Solar storms impact electrical power grids by causing quasi-DC neutral point currents in transformers. These currents lead to half-cycle saturation as well as other related and unwanted effects in the grid. To reduce the effect of these currents on the grid, DC-blocking devices can be installed or changes in the grid topology can be made. However, these counter measures often have unwanted side effects or cannot be applied to the grid due to operational restrictions. In this work, a novel mitigation approach, based on the distribution of currents on more transformers, is presented. The number and location of grounded transformer neutral points is optimized, taking grid related constraints such as the minimal number of transformer connections into account. It is shown that the algorithm can effectively reduce the stress on transformers without any additional assets and thus increase system security