New insights in the use of the DC model for steady-state analysis of power systems

The DC model for the steady-state electrical power flow is evaluated from the double viewpoint of its modeling adequacy and its flexibility as an aid to analysis and planning in generation and transmission systems. Two new results are obtained: -The DC model is shown to be conservative with respect to the more accurate AC model (where losses are neglected) in checking for line overloads. -A formula is obtained for the derivative of the aggregate loss of load (or, more generally, the minimum cost of curtailment), as calculated with the DC model, with respect to any branch susceptance. It is felt that the first result adds credibility to the DC model, while the second one enhances its potential as a tool for decision-making.