【摘要】 对保护用电流互感器在大电流时的性能进行校验时一般采用含铁芯的电磁式互感器作为标准。但电流较大时,电磁式互感器铁芯体积大、制造困难,且剩磁现象严重,导致其误差变大。为此,提出了一种基于空心线圈互感系数自校验原理的交流大电流校验系统。在小电流时,该系统利用铁芯线圈的输出来校正空心线圈的安装等外界因素可能造成的误差。由于空心线圈的线性度好,校准后的空心线圈可作为大电流校验时的电流标准。空心线圈的输出需要积分还原,采用基于直流负反馈原理的数字积分算法,有效克服了传统模拟积分电路和数字积分的零漂、时漂和直流偏移问题。测试结果表明,该系统在电流500 A~50 kA范围内可达到0.1级的准确度。更多还原

【Abstract】 Accuracy calibration of protective current transformer carrying large current is generally performed using electro-magnetic transformers equipped with iron core as the standard current transformer. However, it is difficult to manufacture the iron-core, and it has a large volume for measuring heavy current and has serious residual magnetism which causes increasing error. Thus we proposed a heavy current calibration system based on the self-calibrating mutual inductance of air-core coil. The system adopted an iron-core coil to correct the error of air-core coil at small current, which might be caused by external factors such as installation and so on. Then the calibrated air-core coil was used as the standard current transformer at heavy current for its good linearity and wide dynamic range. Since the air-core coil needed to be integrated, the system employed a digital integration algorithm based on DC negative feedback, which could effectively overcome the zero drift, time drift, and DC offset of traditional analog integration and digital integration. Test results show that the system’s accuracy reaches up to class 0.1 in the current range of 500 A~50 kA.更多还原