Evaluation of the GIC module in PSS/E

Abstract

Geomagnetic Induced Current (GIC) is a known threat to power systems. Previously there has been no commercial software available to simulate the stress this causes on the power systems. With the increased demand of investigating GIC scenarios Siemens PTI has developed a GIC simulation module within its software PSS=E. This Master Thesis evaluates this GIC module. In order to perform simulations a fictive grid situated in the middle and south parts of Sweden was created with Oskarshamn as the main target of investigation. For this evaluation the student version of PSS=E was used which limited the power system to 50 buses. Therefore only the 400/135 kV transformers were evaluated together with the transformers from the generating units. The simulations were performed for three different cases with three storm scenarios. The cases represented the transforming units in the early 90's and the upgraded transformer units for today with and without a grounding resistance at Oskarshamn. The storm scenarios evaluated had an electric field strength at 5, 10 and 20 V=km at a storm direction between 0 360 stepped with 10. The results gathered from these simulations were compared with measured data to review the precision of the GIC module. From the simulations it was noted that the transformer types in the power system were subjected to the expected stress, that is that the reactive power losses at the transformers were highly dependent on the transformer core type. The simulated GIC at Oskarshamn differed from the measured peak value with 6%, however the precision in the resulting reactive power losses at each transformer type in the system could be questioned. That is because the GIC module uses a transformer model with a linear relationship between the subjected GIC and the reactive power loss. It is therefore recommended that the user, depending on the aim of precision, uses a more complex transformer model.