Geometrical Observation Indexes of Distribution System Security Region

This paper proposes the geometrical observation indexes, including volume, surface area and volume to surface area ratio (VSR) and roundness of DSSR. Firstly, the two most basic geometrical indexes are proposed, that is the volume and surface area. Volume is defined as the size of DSSR and surface area is defined as the size of all security boundaries. Secondly, the algorithms of volume and surface area based on Monte-Carlo simulation sampling are proposed respectively. Thirdly, the relationship between DSSR volume and surface area is studied, and a new index, volume to surface area ratio (VSR), is proposed, which is the reciprocal of the surface area required to form a unit volume. By comparing the VSR of DSSR with geometrical figures, the roundness of DSSR is defined, that is, the degree of closeness from the DSSR is to the circle. Finally, different distribution networks are used to verify the proposed concepts and methods. We find that two distribution networks with the same total supply capability have great differences in DSSR. Therefore, the results show that the new indexes can distinguish planning schemes more effectively and have direct guiding significance to the evaluation and planning of secure and efficient distribution network.