Modelling and Analysis of Delta-connected Power Transformers Grounded Using Zig-Zag Transformer

Since some grounding transformers seem to be damaged due to the failure of the medium voltage cables in Turkey’s 1st region, it is necessary to investigate the system behavior, thoroughly. The main substation is modeled in detail, as well as the high voltage and medium voltage equipment connected to this. The Wye-delta transformer is grounded by a Zig-Zag transformer on the delta side. However, records indicate that the grounding Zig-Zag transformer was damaged by high fault currents on the medium voltage side. An appropriate and feasible solution is proposed by simulating and analyzing the possible scenarios. PSCAD software is used to simulate the event and examine the proposed solution. The final step of the analysis is to validate the results related to fault currents using the real-time simulation tool, RTDS through RSCAD software.