Analysis of Voltage Distribution Characteristics in Urban Distribution Networks with High Cable Penetration Rates

Driven by environmental, spatial, and reliability constraints, the retrofitting of overhead distribution lines and the construction of new underground cables have been continuously advancing in urban areas, leading to an increasingly prominent trend of high cable penetration. Compared to overhead lines, distribution cables exhibit significantly higher ground capacitance, which generates charging power that can result in severe issues such as reactive power backfeeding and voltage rise at the feeder ends during light or no-load conditions. To address these challenges, this paper first establishes a power flow (PF) calculation model for distribution networks that incorporates the effect of ground capacitance. Considering the model's non-convex and nonlinear characteristics, reformulations using variable substitution and second-order cone relaxation are applied. Furthermore, taking into account operational constraints such as node voltage and line power limits, an approximate optimal power flow (OPF) algorithm is proposed for highly cabled distribution systems. Finally, the effectiveness of the proposed method is validated using a modified IEEE 33-bus distribution system.