Installation of such reactive power compensation devices as the STATCOM is one of the effective methods in solving the voltage fluctuation.The prerequisite for determining STATCOM compensation capacity is to calculate maximum voltage variation.The empirical formula for calculating the maximum voltage variation at the current project is neither accurate normeets the definition of voltage variation in China national standard.In order to get more accurate the maximum voltage variation calculation result complying with the national standard

a range traversal searching algorithm to calculate the maximum voltage changes is presented in this paper.The method firstly performs selective filtering of the original data sequence.Then the numerical differentiation principle is used to determine the sequence of voltage fluctuation extremes.The boundary point processing is performed on the extreme value sequence and all the extreme points of the voltage variation are calculated.Finally

the ratio of the 95% probability large value of the extreme difference to the nominal voltage is determined as the maximum voltage variation.It is verified by the simulation examples and field test data that the method in this paper not only meets the requirements of the national standard

but also the results are more accurate.