基于滤波插值抽取方法的变压器差动保护以太网数据接口

Ethernet data interfaces for transformer differential protections based on filtering-interpolation-extraction method

针对电子式互感器数字输出接口(合并单元)的数据输出率与成熟变压器差动保护算法的交流采样频率不一致的问题,分析了直接采用Lagrange线性插值方法从原始数据序列抽取所需数据的方法中存在的频率混叠现象,提出了滤波插值抽取的方法,对其进行了性能分析。给出了以太网数据接口实现的方案,包括以太网接口的硬件结构及简化的滤波插值抽样处理的软件实现方法。该数据接口在保留原有成熟保护算法的前提下提高了采样值的计算精度,为保护的动作性能提供了可靠保证。

To solve the problem that the data rate of the electronic current/voltage transformer＇s digital output interface （merging unit） differs with the AC sampling rate of the sophisticated transformer differential protection algorithm, the frequency alias phenomenon existing in the extraction of required values from the original data by applying the Lagrange linear interpolation algorithm directly is analyzed. The filtering-interpolation-extraction method is proposed consequently, and its performance is analyzed. On this basis, a scheme to realize the Ethemet data interface is pro- posed, which includes the hardware structure of the Ethernet interface and the simplified processing method of filte- ring-interpolation-extraction realized by software. The data interface improves the calculation accuracy of the sampled value with the sophisticated protection algorithm remained, and ensures reliable operation of the protection.