For multi-rate source, protection receives the digital signals with different sampling rates from communication interface, resulting in the different sampling rates on the two sides of differential protection and errors. This paper concentrates mainly on resampling method for input signal with different sampling rates in multi-rate source, and proposes the frequency domain transformation resampling method. Firstly, performs half-wave Fourier transformation on protection sampling signal. Secondly, processes the frequency domain resulting from the transformation based on the difference in sampling rates. Thirdly, changes the processed frequency spectrum to the time domain with inverse transformation, obtaining resampled signal. Comparing with the current method for resampling, this method can not only utilize the waiting time data of R times of continuous distinguishing of differential protection of sampled values efficiently and increase the precision of resampling, but also limit the error in resampling to a low level when signals contain a wealth of high-order harmonic, as well as archive zero-delay for resampling output. The average error rates of resampling precisions during the system normal and during external fault removal, showed by the simulation, are only 0.50% and 1.10% separately, both are better than traditional method of time domain resampling.%多数字源环境下，保护从通信接口中接收不同采样率的数字量，导致差动保护两侧采样率不一致，无法正常运行。针对此问题，该文研究多数字源不同采样率输入信号的重采样问题，提出频域变换重采样方法，先将保护采样信号进行半波傅里叶变换，再根据采样率的差异对变换后的频域进行处理，最后将处理过的频谱反变换到时域，得到重采样后的信号。该方法与现有重采样方法相比，不仅可以将采样值差动连续尺次判别所用等待时间中的数据很好地利用起来，增加重采样的精度；而且可以很好地在信号包含的高次谐波较丰富时，将重采样误差控制的很低；并相对于传统重采样算法，让重采样信号输出达到零延时。仿真验证了该方法在系统正常及外部故障切除时的重采样精度，平均误差率仅分别为0．50％和1．10％，均优于传统时域重采样方法。
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