Empirical Study of the Influence of AC/DC Touch Fault on Transformer Differential Protection

In practical engineering, the cross and crossing of AC and DC lines are more common at present. The communication lines are complex, especially in the South. With many DC projects, the cross over phenomenon of AC and DC in the China Southern Power Grid is more obvious. This paper is based on the practical PSCAD simulation model of Jin-Zhong converter station, built a simulation model of AC and DC concomitant systems, and selecte 220 kV and 500 kV communication systems as typical scenarios for analysis by simulation of metal touch faults outside the AC transformer protection range. According to the simulation waveform, The characteristic analysis results of transformer differential protection are given in the end.