中文说明：利用逐步倒推法进行电网规划。分第一和第二两个阶段，第一阶段是通过编程获得最小经济网络；第二阶段是通过编程获得最后的最优网络。
English Description：
Backward stepwise method for network planning. First and 22 stages, first phase is obtained by programming with minimal economic networks; the second phase is obtained by programming the final optimal network.