Studies on the section thermal limits based on security region

This paper proposes a method for calculating and analyzing section thermal limits under the condition of the security “N-1” criterion and forms the security region in multi-dimensional space. By calculating each generator´s power transfer distribution factor (PTDF) on section lines, using the DC load flow model, the sensitive generators to the section thermal limits can be identified. With sensitive generators output as the axes of multi-dimensional space, the thermal limit points can be obtained under the condition of the security “N-1” criterion. Then the thermal stability security boundary is formed when those thermal limit points are fitted in the multi-dimensional space. The thermal stability security boundary depicts the variation of section thermal limits with each sensitive factor output change and reflects the specific impact of sensitive factors to section thermal limits. The proposed method has been applied in a real power grid in the south of China.