This work proposes a new method based on the Hermite transform with the aim of identifying transient events in power transformers caused by energizations and current transformer (CT) saturation. The Hermite transform is a signal processing technique that allows the representation of signals in the time–frequency domain as well as at multiple resolution levels. Gaussian derivatives analyze the signals in the proposed scheme according to the Hermite transform theory. The newly introduced approach is based on a differential scheme considering three functions, the first one to analyze the positive half-cycle and the second one for the negative half-cycle. The latter is a new blocking function for the detection of transient conditions, that is, the operation command is disabled; otherwise, the third function will confirm if the condition is an internal fault. To validate the performance of the proposed method, several fault conditions are addressed, such as load switching, internal and external faults, current transformer saturation, and single-phase-to-ground faults. Results show the effectiveness of the proposed method, which improves the differential protection performance to discriminate transient conditions from internal faults.

这项工作提出了一种基于Hermite变换的新方法，其目的是识别由通电和电流互感器（CT）饱和引起的变压器瞬态事件。Hermite变换是一种信号处理技术，可以在时频域以及多种分辨率级别上表示信号。高斯导数根据Hermite变换理论分析提出的方案中的信号。新引入的方法基于一种考虑了三个功能的差分方案，第一个用于分析正半周期，第二个用于负半周期。后者是用于检测瞬态条件的新阻止功能，即，禁用了操作命令。除此以外，第三个功能将确认条件是否是内部故障。为了验证所提出方法的性能，解决了几种故障条件，例如负载切换，内部和外部故障，电流互感器饱和以及单相​​接地故障。结果表明了所提方法的有效性，该方法提高了差动保护性能，可将瞬态条件与内部故障区分开。