Study on Distribution Reliability Considering Voltage Sags and Acceptable Indices

In modern power systems, more sensitive loads appear. The impact of voltage sags on customers cannot be ignored. With the opening of electricity markets, it is necessary to modify and supplement the reliability indices to consider the influences of voltage sags. In this paper, three supplementary indices are proposed, that is: 1) event time; 2) sag energy; and 3) cost of events. Furthermore, we try to redefine the traditional reliability indices on service. These indices may be useful today and in the future as well. Computer simulation results show that voltage sags do affect reliability indices, which change the value of the third digit of the decimal part of reliability indices. The higher the reliability level is, the larger the impact of sags on reliability is