Which type of power transformers are primarily affected by geomagnetic disturbances (GMDs)?

Wye connected transformers are primarily affected by geomagnetic disturbances (GMDs) due to their grounding and connection configuration. In a Wye connection, the neutral point is accessible and can be grounded. When GMDs occur, they induce geomagnetically induced currents (GICs) in the power grid. These currents can flow through the neutral point because it is grounded, leading to an increase in the magnetic field in the transformer. The induced currents can saturate the core of the transformer, which can cause overheating and potentially damage the transformer.

Additionally, Wye connected transformers are often more susceptible to GICs because they are typically used in high-voltage transmission systems where the introduction of these currents can have significant impacts. In contrast, Delta connected transformers do not have a neutral point and are less prone to GIC impacts. Other types mentioned, like open-loop and radial transformers, do not specifically relate to the effects of geomagnetic disturbances in the same way that Wye connected transformers do. Understanding the implications of transformer connections in relation to geomagnetic disturbances is vital for operators to protect equipment and ensure system reliability.