Linear interpolation process and its influence on the secondary equipment in substations

Linear interpolation algorithm is widely used to achieve data resampling function in the secondary equipment of digital substations. In order to analyze the transfer characteristics of linear interpolation, this paper presents an equivalent analysis process for the algorithm based on interpolation auxiliary signal. Results show that for sampling frequency conversion, the linear interpolation process performs as a fixed low pass filter. While for data synchronization whose sampling frequency stays unchanged, magnitude of the signal after interpolation depends on the position of the interpolating points. In addition, this paper discusses the influences of linear interpolation on the secondary equipment. It takes little effect on protection equipment. However, it has negative influences on the performance of measurement equipment and merging unit.