Slack line flow sessions can appear in a long slope pipeline.
大落差管道在运动中，其下坡段可能出现不满流管段。
2
Firstly, the problem of reactive power constrains of generator at slack bus is studied, and a load margin algorithm of continuation power flow of reactive power constrain at slack bus is proposed.
So, the problem of reactive power constrains of generator at slack bus should be considered when calculating the load margin and critical voltage by using the method of continuation power flow.