Transformer models and meters in MATLAB and PSCAD for GIC and leakage dc studies

Abstract

Geomagnetically induced currents (GIC) caused by abnormal space weather have traditionally been modelled as balanced dc in low-frequency transients studies. Existing transformer models can be used to investigate a power system with GIC but the extent to which these models are consistent is unclear. This paper investigated the differences between the three-phase five limb (3p5L) power transformer models in MATLAB Simulink and PSCAD/EMTDC when they were subjected to dc (dcGIC) and low-frequency GIC (acGIC). The simulation protocol used a simple 4-bus power system with a generator, two transformers, a line, and a PQ load. An IEEE 1459 power calculation block was developed in MATLAB for non-ideal conditions whereas waveform data was post-processed from the PSCAD simulations. The results showed that even though the transformer models were calibrated with the same magnetization characteristics, the 3p5L PSCAD models with inter-phase magnetic coupling yielded a slightly different magnetization curve for each phase. By contrast, the MATLAB model yielded the same magnetization curve for each phase under the same conditions. As a result, there were differences in the performance with dc or acGIC, with the PSCAD model being more responsive to phase unbalance, simulating greater distortion in the transmission line, and voltage drop at the end.