EMO:How EMO models SFT constraints

Automatic SFT constraint generation in EMO

The aim of automatic SFT constraint modelling in EMO is to model the SFT constraints that are generated as part of the dispatch and pricing solution in SPD. These constraints are designed to avoid thermal overloading of a line in the event of the unexpected outage of any other line. SFT constraints appear in the dispatch and pricing optimisation model as linear constraints between two lines. For example:

 -0.902*OHK_WRK.1+1.274*THI_WKM1.1 <= 605.79

In this case THI_WKM1.1 is the line being protected from overload and OHK_WRK.1 is the line which may cause overload in THI_WKM1.1 if it has an outage. The general form of the SFT constraint is

 Equation 1.  \(A F_{M} + B F_{C} \leq C\)

Where \(F_{M}\) is the flow on the protected line and \(F_{C}\) is the flow on the contingent line. The physical nature of the SFT constraint depends on various characteristics of the line being protected, the thermal environment and the mitigating measures available if an outage occurs. The constraint can be expressed as a function of the loading on the line before an outage occurs (pre-contingent) and the loading after an outage occurs (post-contingent). The higher the line is loaded pre-contingency the greater its expected temperature, giving it less capacity to absorb extra power in the event of a contingency