A numerical method is presented to calculate the current and potential of impressed current cathodic protection system for the buried steel pipeline protected by two cathodic protection stations jointly. A resistance circuit with DC supplies is usd to simulate the system through the discretization scheme. Impressed potential and current along the pipeline are found out by mesh-current method. The numerical results have a good agreement with the analytic results and measured ones from Tianjin to Beijing aviation kerosene pipeline. The numerical results show that the coating damage causes increase in protective current and decrease in absolute value of potential along pipeline. The coating damage has less effect on the position where absolute value of potential is minimal, while the output voltage of DC supplies has more on the position. The nearer the location of coating damage is to a cathodic protection station, the bigger the difference of protective currents of the two stations is.

Under condition of the possible locations of the pump station were determined. And    applied directed edge-weight graph to describe the optimization problem of the products pipeline, and graph theory was used to analyze the problem. The candidate pump station locations were taken as the vertices and the total cost of the pipeline system between the two vertices were looked as the edge-weighted. Then algorithm recursively calling the Dijkstra algorithm was designed and analyzed to obtain N shortest paths, so the optimal alternative and the quasi-optimal alternatives were obtained at the same time, these alternatives can be used to compare by the designer. Moreover, the algorithm was tested by a real example; it can meet the need of real application. Applied this method can avoid adjustment the locations of the pump station, and more fit the need of the engineering. It also can be extended to the other long-distance oil or gas pipeline optimal design.