谐波对平均值原理仪表测量的影响分析

Analysis on the Effect of Harmonic on the Instruments with Average Value Principle

非线性负载的广泛应用,导致电力系统中的谐波日益严重。电力系统中使用的交流电压表和电流表通常采用整流式仪表,其工作原理是对电网电压和电流的平均值响应,利用平均值和有效值的比例关系从而得出信号的有效值。由于是按50Hz标准正弦波设计,当电网电压中有高次谐波或者负荷电流中有高次谐波时,必然会影响其正常工作。因此采用平均值原理的仪表测量非正弦周期信号电压和电流的有效值,存在原理性的误差。基于其工作原理,定量分析不同谐波下的误差及一定谐波含量下误差的大小。通过分析结果,建议采用真有效值原理的电压表和电流表。

The application of non-linear load produces a mass of harmonics. The AC voltage meter and the AC current meter used in power system are usually rectifying instruments, which adopt principle of responding to the average value of voltage and current and get the virtual value by using of the proportion between the average value and it. Because they are designed based on the 50 Hz standard sinuous wave, the principle error will occur when the voltageof power system and the current of loads include harmonic. Based on their working principle, this kind of error is analyzed quantificationally. And the result shows that it can not be neglected. The voltage and current meters with real virtual value are proposed.