The type of voltage sag is an important feature of sag events

which provides decision-making information for fault type identification at grid side

withstand capability test of sensitive equipment of sensitive equipment at user side and formulation of voltage sag control scheme etc. In this paper

five kinds of typical methods for calculating voltage sag types are analyzed and different algorithms are applied to simulation data and 216 sets of measured data. Based on the calculation results

the problem existed in the algorithms is raised. It is shown by the calculation results of simulation and measured data that larger phase jump and shallower drop depth are important factors affecting the results of the algorithm. When different algorithms are applied to the actually measured data

the results have big difference and have not yet reached the practical requirements of the power system. It is also necessary to develop new methods for calculating the sag type so to apply them to power quality monitoring systems.