模拟量输入合并单元计量性能测试研究

Metering Performance Test of Analog-Input Merging Unit

目前对模拟量输入合并单元的计量性能研究较少,现有合并单元测试规范中与误差相关的部分均参照电子式互感器标准制定,难以满足计量性能测试的要求,限制了数字化电能计量技术的发展。为研究模拟量输入合并单元的计量特性,从信号流程角度,分析了模拟量输入合并单元的误差环节,比较了模拟量输入合并单元与电子式互感器和电子式电能表的结构异同,总结了计量特性误差影响因素。并以基本误差为例,按照不同标准对2台不同厂家生产的标称0.2 S级准确度的合并单元进行了单相和三相误差测试。测试数据显示单相测试和三相同时测试的结果有差异,说明各通道相互之间有影响,且输入信号越小,相互影响越大。针对现有合并单元测试规范不能正确反映计量性能的问题,提出评价模拟量输入合并单元计量性能时,不能仅仅参考电子式互感器标准,还应参考电子式电能表检定规程增加计量性能相关测试项目,完善计量用合并单元的相关测试规范。

At present the progress related to the research on the metering performance of analog-input merging unit is seldom reported. In existing test specification for the merging unit the content related to the measurement error is drafted by reference to the standard for the electronic instrument transformer, so it is hard to meet the requirement of metering performance test for the metering performance of the merging unit, therefore the development of digital electric energy metering technique is restricted. To research the metering performance of the analog-input merging unit, from the respective to the signal flow the element causing the error in the analog-input merging unit is analyzed and the similarities and differences among the structures of analog-input merging unit, electronic transformers and electronic watt-hour meter are compared and the factors impacting the metering performance error are summarized. Taking the basic error for example, according to different standards the single-phase and three-phase error tests for two analog-input merging units with nominal accuracy of 0.2% respectively produced by different manufacturers are performed. The test data show that there are differences between the results of single-phase measurement and the results of three-phase simultaneous measurement, it means that there are influences among the channels and the smaller the input signal, the greater the interaction is. In allusion to the defect in existing testing standard for the merging unit that the measurement results cannot correctly reflect the metering performances, it is suggested that during the assessment on the metering performance of the analog-input merging unit, not only the testing standard for the electronic transformer should be referred, but also the verification regulation for electronic watt-hour meter should be referred, and the testing items related to the metering performance should be added to perfect the related testing specification of the merging unit for the measurement.