As a starting point with the provisions of the international standard, this paper interprets the impact test of DC and even harmonics. Through the measurement mechanism of watt-hour meter in harmonic environment, and com-bining with the definition of RMS, it sums up the component current which participates in the calculation as for full wave voltage waveform and current waveform of half wave. The overall grasp of test and further summary of the mean-ing of the trial provide theoretical basis for the person of measurement test.%解读国家标准中直流偶次谐波影响试验的规定，通过电能表在谐波环境下的计量机理，结合有效值的定义，总结出当电压波形为全波、电流波形为半波时，参与计算的电流分量，推导出直流偶次谐波试验中的参考电流的大小。本试验的整体把握与深入总结，为计量检测人员提供理论依据。
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