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Current transformers (CTs) may saturate during internal fault, external fault, over excitation, exciting inrush current and other phenomena, which would cause protection relay malfunction or even tripping. As a result, it is vital to mitigate the adverse effects of CT saturation. By analyzing the secondary current waveform, which has abrupt changes where saturation begins and ends, the paper proposes...
This paper presents a novel algorithm for secondary current signal segmentation of saturated current transformer (CT) using three morphological gradient-based detectors. The saturation onset detector is used to monitor the occurrence of saturation and then trigger the positive/negative segmentation detector, which are designed to locate the starting point and the ending point of CT saturation. The...
Sympathetic interaction between transformers would lead to mal-operation of transformer differential protection. Based on the fact that the waveform of internal fault current has the sinusoidal features while the sympathetic inrush has not, a weighted mathematical morphological method is proposed for the identification of sympathetic inrush. In the simulation studies, the identification results have...
This paper proposes a novel method to detect the saturation intervals of current transformer (CT) secondary current. The method features the waveform properties of the distorted secondary current, which has abrupt changes where saturation begins and ends. Two algorithms, the improved morphological gradient and the morphological decomposition, are designed to extract the saturation intervals, respectively,...
This paper proposes a novel scheme to detect the saturation of current transformers (CTs) for protection blocking. The scheme modifies the morphological skeleton method and applies it to analyze the shape information of CT secondary current. Afterwards, two indices are introduced to determine the existence of saturation. Simulation studies under a variety of fault conditions have been conducted using...
The saturation of a current transformer (CT) will cause severe distortion in the secondary current. Each fundamental cycle of the secondary current consists of two portions, the unsaturated portion and the saturation. This paper proposes a morphological scheme for the detection of the saturations and an embedding and optimization scheme for the removal of the exponential decaying DC offset and the...
This paper presents a novel method for current transformer (CT) saturation detection and compensation. In the method, CT saturation characteristics are represented by a partial nonlinear regression model. The parameters of this model can be estimated rapidly and accurately using both unsaturated and saturated sections of the waveform of a secondary fault current, even in a heavy saturation scenario,...
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