January 2020, by Estefania Ruiz
Every year, there are certain solar events that take place. While we all back here on Earth have probably never seen or heard about this phenomenon, these events are the result of the Sun changing its magnetic polarity every 11 years, which is known as a “Solar Cycle”.
Solar flares are a huge burst of energy that usually comes hand in hand with the release of huge streams of charged plasma that travels at millions of miles per hour. These are called CMEs (Coronal Mass Ejections). Depending on the magnitude and direction of the CMEs, these might cause a Geomagnetic Disturbance hitting Earth with tons of electrical charges and magnetic fields at a speed of approximately three million miles per hour. Geomagnetic Disturbances can affect the power grid, interfere with GPS, or even satellite- based communications systems.
GMD (Geomagnetic Disturbances) happens when the charged particles expelled by the Sun affect the geomagnetic field. The most critical GMDs are associated with Coronal Mass Ejections (CMEs). Variations in the geomagnetic field cause large scale electric currents to appear in the ionosphere2, near the Earth magnetic poles. These currents are also known as “Electrojets.” Geomagnetic field variations, caused by solar activity, create electrojets, which in turn induce electric fields onto the surface of the Earth, generating what is called GICs or Geomagnetically Induced Currents. These GICs can ultimately cause blackouts.
Prolec GE developed a GIC Resistant Transformer that meets the guidelines described on the C57.163 IEEE Guide. In order to ensure the capability of transformers while under a GMD event stays intact. Transient models have made possible to design transformers able to withstand GIC pulses while complying with the recommended thermal limits and guaranteeing transformer reliability. Prolec GE has developed mathematical models designed to comply with IEEE C57.163 and provide information required to conduct a power system stability assessment as required by Reliability Standard TPL-007-1.
Prolec GE has developed magnetic models for different core topologies, being able to determine the following with these models:
These results have been used as a baseline on how GIC may impact the integrity of transformers during their life cycle. Finite Element and thermal models are used to analyze losses in metallic components. This analysis provides us with temperature profiles, which, based on the results obtained, help us decide what changes need to be implemented during the Design Process.