前推回代法已知配电网的始端电压和末端负荷，以馈线为基本计算单位。

最初假设全网电压都为额定电压，根据负荷功率由末端j向始端k逐段推算，仅计算各元件中的功率损耗而不计算节点电压，求得各支路上的电流和功率损耗，并据此获得始端功率，这是回代过程。

再根据给定的始端电压和求得的始端功率，由始端向末端逐段推算电压降落，求得各节点电压，这是前推过程。如此重复上述过程，直至各个节点的功率偏差满足允许条件为止。(The forward and backward substitution method is based on the feeder, which is used to calculate the initial voltage and terminal load of the distribution network.



Initially, assuming that the voltage of the whole network is rated voltage, the power loss of each component is calculated step by step from the end J to the beginning k, instead of the node voltage, and the current and power loss of each branch are calculated. Based on this, the starting power is obtained. This is a process of substitution.



Then, according to the given starting voltage and the calculated starting power, the voltage drop is calculated step by step from the beginning to the end, and the voltage of each node is obtained, which is the forward process. Repeat the above process until the power deviation of each node meets the allowable conditions.)