Transformer excitation inrush current and fault differential current recognition method based on Hausdorff distance algorithm

Abstract

The invention provides a transformer excitation inrush current and fault differential current recognition method based on a Hausdorff distance algorithm. The transformer excitation inrush current and fault differential current recognition method comprises the steps of: acquiring secondary currents of current transformers at two differential protection sides of a transformer on each cyclic wave N point, and form a differential current signal sequence I; judging whether a value of the differential current signal sequence I exceeds a setting valve of a differential protection starting component, and starting a criterion disclosed by the invention for distinguishing a fault differential current and an excitation inrush current if the value exceeds the setting value differential protection starting component; judging and acquiring an extreme value of the differential current signal sequence I by adopting a 1 / 4 cyclic wave data window, regarding a differential sequence A after per-unit treatment as an edge feature point of a Hausdorff distance algorithm object graph, regarding a standard sine sequence B with amplitude being 1 as an edge feature point of a Hausdorff distance algorithm template graph, comparing an Hi value with a set Hausdorff distance threshold value Hset, and conducting protection action if the Hi value is less than the threshold value; and blocking protection if the Hi value is greater than the threshold value. The transformer excitation inrush current and fault differential current recognition method is used for directly judging difference of waveform pattern overall features of inrush currents including symmetric inrush currents, and ensures correct action of transformer differential protection.

Description

technical field [0001] The invention relates to a transformer excitation inrush current and fault differential current identification method based on a Hausdorff distance algorithm, and relates to the field of transformer differential protection. Background technique [0002] The second harmonic braking criterion is widely used in existing transformer differential protection to identify transformer excitation inrush current. However, the actual operation shows that the second harmonic braking criterion has limitations. For example, when the differential current is a symmetrical inrush current, the second harmonic content is low, which will lead to the failure of the second harmonic braking criterion and poor performance. When the transformer has a high-resistance internal fault and no-load closing, the differential current contains an obvious inrush current except for the fault current, which will increase the second harmonic content and cause the second harmonic braking cri...

AI Technical Summary

Problems solved by technology

The former involves a complex mathematical analysis method, which requires a large amount of calculation and is complex to implement and has high requirements for the hardware of the device; the latter has high requirements for the smoothness of the differential flow waveform, so it is necessary to filter the aperiodic components and harmonics contained in it. In addition, the algorithm itself needs at least half to one cycle time window, so the identification process has a long delay, and it can only respond after a delay of at least 3 / 4 cycle when an internal fault occurs.

At the same time, the above algorithm has high requirements on the data integrity of the sampling points of the differential flow sequence, and the loss of some sampling points may have a great impact on the algorithm results, resulting in misjudgment of protection

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