Abstract: The grid integration of distributed photovoltaics gives rise to bidirectional power flow in low-voltage station areas. Coupled with three-phase load imbalance and the time-series mismatch between photovoltaic output and power load, the variation pattern of line loss in station areas presents complex characteristics. To clarify the influence mechanism of multiple factors on line loss and construct an accurate deduction model, a 15-node joint simulation model for photovoltaic-station area systems is built based on MATLAB/Simulink, and comparative tests are conducted from four dimensions: grid-connected position, load penetration rate, load distribution and time-series operating conditions. The results indicate that 60% photovoltaic load penetration rate serves as the critical threshold for power flow reversal, and the overall error of the two-time-scale line loss deduction model proposed in this paper is below 2%. The research conclusions can provide quantitative support for photovoltaic layout planning and on-site line loss management of low-voltage station areas.