Power supply via 10 kV lines is generally achieved in a radial branch structure, and low voltage problems are prone to occur at the end of the branch lines. The analysis of typical areas with safe power supply via 10 kV lines is the basis for the study of distribution network expansion and planning methods. The voltage drop characteristics of 10 kV lines are analyzed, and a simplified calculation method for the voltage drop along the line is derived. The power supply areas of the 10 kV distribution network are decomposed into four typical supply area models: rectangular, diamond-shaped, front-triangular, and rear-triangular. Each model uses the main lines as the central axis, with the branch lines bearing balanced loads. The boundary voltage drop of each typical area is analyzed, and the relationship among the total load, line type, and boundary voltage drop is established, thereby determining the maximum area of each type of typical power supply area under boundary voltage safety constraints. The analysis of typical power supply areas and their corresponding safe power supply capacities via 10 kV lines provides a theoretical basis for substation siting, grid layout, and line type selection in newly developed distribution areas, with both theoretical significance and engineering value.