The distribution system security region(DSSR)is a new method of distribution network security evaluation

but this method has not given all the information obtainable from N-1 simulation. The DSSR method is enhanced and compared with N-1 simulation. Firstly

the principles of two methods are analyzed: the N-1 method simulates the components one by one to check whether they satisfy the static security constraints

and the power cut range and residual capacity is used to measure safety degree. The DSSR method calculates N-1 security boundary in terms of network structure and parameters in advance

and judges whether it is secure or not without simulation by judging whether it is inside or outside the DSSR boundary. Then

the safety degree is measured by the security distance. Secondly

an enhanced DSSR method is proposed to obtain all the results of N-1 simulation

including the sorted contingency set

overload element set and the degree of the overload. Finally

a numerical example comparing the two methods is given to illustrate that the enhanced DSSR method is correct and highly efficient. The proposed work not only extends the function of DSSR

but also reveals the relationship between the two methods while explaining why the enhanced DSSR method has made it possible to obtain all the results from the simulation method. This paper helps to use the DSSR method in practical applications.This work is supported by National Natural Science Foundation of China(No. 51477112)and Program for New Century Excellent Talents in University(No. NCET-10-0624).