Transformer design considerations for mitigating geomagnetic induced saturation

This paper shows that the placement of an auxiliary winding, used to compensate for GIC, significantly influences its rating and that of the associated DC power supply. This paper considers stresses in a banked step-up transformer under system fault conditions. Finite element simulations using the commercially available software package Magnet 5.2 are used to calculate the magnetic flux density distribution and the induced winding voltage per turn under the worst case condition of a short circuited high voltage winding. The variation in the induced voltage is greater if the winding is moved up from its optimal position and less if the auxiliary winding is moved towards the geometric centre of the transformer.