Effect of transformer saturation on the DC distribution of AC power system

Aiming at the phenomenon that occurrence of half-wave saturation in transformer magnetizing current can be caused by magnetizing branch saturation under DC bias conditions, which will result in the DC component current emergence in magnetizing current, we researched the effect of the DC component on the distribution of the DC bias current in the transformer neutral point. The formation mechanism of DC current in the neutral point of three-phase transformer in the case of DC bias was analyzed. A transformer DC bias simulation model was established based on the PSCAD/EMTDC platform.Moreover, the compositions of DC currents in transformer neutral point with DC bias considering and regardless of the transformer saturation were studied, respectively. Furthermore, DC distributions in transformer neutral points of Y region, which was calculated on the basis of DC bias simulation model without taking the transformer saturation into account, could be amended. Simulation results show that transformer saturation has infeed effect on the DC bias in transformer neutral point. In addition, the prediction accuracy of DC distribution in the AC power system can be improved after taking transformer magnetizing branch saturation into account. © 2016, High Voltage Engineering Editorial Department of CEPRI. All right reserved.