Abstract:With digital sampling in smart substation, sample data synchronization which is sent by the merging unit is necessary for the IEDs. For real-time tracking and measuring the operating frequency of the power system, the sampling data’s resampling is often required by using interpolation algorithm. In order to analyze the error caused by dual interpolation, this paper analyzes the theoretical error of Lagrange and Newton interpolation algorithm, and quantitative analyzes of impact for high order harmonic is provided. The compensation due to interpolation algorithm is calculated according to the analysis. In the end, the method of improving the accuracy of high order harmonic measurement based on interpolation algorithm is proposed.