An ECT(Electronic Current Transducer) calibration system is designed based on virtual instrument technology to test the analog output of high-precision ECT. Its overall structure is introduced and the influence of frequency variation on signal extraction is analyzed for the normal working frequency range of ECT measurement channel,i.e. 49.5～50.5 Hz,stipulated by IEC. The fourth-order triangle convolution window algorithm is used to extract the signal detected. Compared with FFT(Fast Fourier Transform) recommended by IEC60044-8(ECT),it reduces the leakage effect error of non-integer-period sampling,resulting in higher accuracy. Experiment shows that,when the frequency deviation is within 50±0.5 Hz,the ratio error reaches the order of 10-4 and the phase error reaches the order of 10-2 minutes,meeting the calibration demand of 0.2 S class ECT.%根据测量用电子式电流互感器(ECT)的校验要求,研制了一种基于虚拟仪器的ECT模拟输出校验系统.介绍了该校验系统的整体构成,针对IEC标准规定的ECT测量通道正常工作频率范围即49.5～50.5 Hz,研究了工作频率变化对信号提取的影响.采用4阶三角卷积窗的FFT算法来提取被校验的信号,与IEC60044-8(ECT)中推荐的FFT算法相比,该算法可以有效减少因非整周期采样造成的频谱泄漏误差,具有更高的准确度.实验表明:当频率波动范围为50±0.5 Hz以内时,校验系统比差可达到10-4,角差可达到10-2分,满足0.2 S级ECT的校验要求.
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