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An analytical calculation method for the reliability sensitivity indexes of distribution systems is proposed to explicitly quantify the impact of various influence factors on system reliability. Firstly, the analytical calculation formulas for the reliability indexes of distribution systems are derived based on the fault incidence matrix (FIM). Secondly, the factors that affect system reliability are divided into two categories: quantifiable parameter factors and non-quantifiable network structure factors. The sensitivity indexes for the quantifiable parameter factors are derived using the direct partial derivation of the reliability calculation formulas. The sensitivity indexes for the nonquantifiable network structure factors are derived using the transformation of FIMs. Finally, the accuracy and efficiency of the proposed sensitivity calculation method are verified by applying them to an IEEE 6-bus RBTS system. This paper sums up the factors that influence system reliability in detail and gives the explicit analytical calculation method for the sensitivity of each factor. Repetitive calculation of the reliability index can be avoided during the sensitivity analysis. The bottleneck that affects the reliability level of distribution systems can be identified efficiently, and valuable information and guidance can be provided to enhance the reliability of distribution systems.

Situation awareness (SA) refers to the process of perception, comprehension, and state projection of the system, elements, and environmental factors within a volume of time and space. The security assessment is an important part of SA for distribution networks. In this paper, the distribution system security region (DSSR) is used for SA for the first time, and a security SA method based on security distance (SD) is proposed. First, based on the existing DSSR, which is defined as the set of all operating points (OPs) satisfying N − 1 security criterion, this paper supplements the N − 0 DSSR satisfying normal operating constraints. Second, calculate SDs between the OP and security boundaries to determine whether an OP is secure. If one is secure, its SDs can give the security margin; while if one is insecure, its SDs can give the degree of insecurity and the fault, or the overload components can be recognized via the cross security boundary analysis. The situation comprehension for the distribution network security is realized through the above-mentioned information. Third, the security level of distribution networks in the future can be predicted by the trends of SDs. Finally, the feasibility and effectiveness of the proposed method are verified by an actual distribution network case.

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