scope:

This guide identifies appropriate voltage sag indices and characteristics on electrical power and supply systems as well as the methods for calculating them. Methods are provided for quantifying the severity of individual voltage sag events (single-event characteristics), for quantifying the performance of multiple events at a specific location (single-site indices), and for quantifying the performance of multiple events for the whole system (system indices). The methods are appropriate for use in 50/60 Hz transmission, distribution, and utilization electric power systems, though there may be applications to systems with other fundamental frequencies.

Purpose

This document identifies and defines different characteristics and indices associated with voltage sags. It does not recommend the use of a specific set of indices but instead recommends the method for calculating specific indices when such an index is used. The large variation in customer equipment's susceptibility to voltage sags and in power providers supply characteristics makes it impossible to prescribe a specific set of indices. Instead, this document aims to assist in the choice of index and to help ensure reproducibility of the results after a certain index has been chosen. The user of this document may decide to calculate the value for just one index or for a number of different indices, depending on the application.