变压器空载电流谐波低频测量方法

变压器空载电流谐波的幅值及成分可以检查铁心的饱和程度,并判断是否有匝间故障。变压器出厂试验时通常采用容量较大的工频电源进行空载电流谐波测量。为了减小试验电源容量,提出一种采用低频电源代替工频电源进行变压器空载电流谐波测量的低频测量法。该方法通过施加两个低频率的电压测量低频下的涡流电流和空载电流谐波幅值,再根据对涡流电流的补偿计算折算至工频下的空载电流各次谐波含量和总谐波含量。并对单相变压器进行仿真和试验验证,采用15Hz的折算结果与工频50H实测的空载电流各次谐波含量K(k)及总谐波含量THDi误差均小于1%。结果表明,所提方法折算准确度高,而且能成倍减小试验电源容量。

No-Load Current Harmonics Measurement of Transformers Using Low-Frequency Method

The magnitude and composition of transformers no-load current harmonics can be used to examine the saturation degree and detect the inter-turn faults. Generally, a large capacity of industrial-frequency (IF) power supply is used to measure the no-load current harmonics content in transformer factory test. In order to reduce the capacity of testing power supply, this paper proposed a method using low frequency power supply to replace IF power supply to measure no-load current harmonics of transformers. Two low-frequency voltages were first applied to obtain the eddy current and no-load current harmonics. The converted current harmonics content and total harmonics distortion (THDi) under IF were then calculated based on eddy current compensation. In addition, the experiments and simulations were conducted on a single-phase power transformer. Compared with the conversion results of 15Hz, the errors of harmonics content and THDidirectly measured under IF are both below 1%. It is shown that this method has high conversion accuracy and can significantly reduce the capacity of testing power supply.