Leakage Current Analysis of BESS Considering Transformer and Cable Impedance

This paper analyzes the magnitude of leakage current due to parasitic capacitance and cable impedance generated by structural characteristics in Battery energy storage systems(BESS). The cable was measured using an LCR meter and employed in simulations and experiments. A leakage current equivalent model was constructed and validated through comparison with experimental data. In the case with no cable impedance, the leakage current path in the IT grounding method includes paths through the LCL filter of the PCS, transformer impedance, and parasitic capacitance. However, when cable impedance is added, it was confirmed that the leakage current magnitude increases because an additional leakage current path through the cable is introduced. Therefore, the magnitude of the leakage current was 43.3 mArms before the cable was added, but after adding the cable impedance, it increased to 159.8 mArms, demonstrating a 3.7-fold increase.