Identification method of excitation inrush current in power system

Abstract

The invention discloses a method for identifying excitation inrush current in a power system, which includes the following steps: high-speed digital sampling of voltage and current, combined application of voltage and current data, taking the horizontal direction as the magnetic field intensity H axis, and the vertical direction as the magnetic induction intensity The equivalent BH curve is reconstructed on the B axis, and the maximum and minimum values ​​of the B and H axis directions of the equivalent BH curve are respectively found, and then a new reference coordinate system is constructed with the new center point D as the origin, and the new The horizontal and vertical axes in the reference coordinate system divide the BH curve into four quadrants, and then calculate the rectangular areas S1 and S3 in the first and third quadrants in the new coordinate system, and calculate the BH curve accordingly. The asymmetry coefficient k_asym, k_asym is compared with the excitation inrush current identification threshold k_th to identify whether it is an excitation inrush current. The invention can improve the reliability and accuracy of the action of the relay protection device.

Description

technical field [0001] The invention belongs to the technical field of power systems, and in particular relates to a method for identifying excitation inrush current in a power system. Background technique [0002] In the power system, inductive equipment such as transformers, reactors, and motors are widely used. Due to the saturation characteristics of the internal silicon steel sheets, excitation inrush currents occur when different voltage phases are switched on. With the development of industry, the capacity of inductive equipment such as transformers is getting larger and larger, but what follows is that transportation has become a bottleneck. Under the condition of satisfying various factors such as weight, volume, and capacity, it has gradually entered the limit manufacturing stage, such as In order to reduce the weight and cost, the design of the transformer uses silicon steel sheets with high magnetic permeability, and the operating point corresponding to the rated...

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Problems solved by technology

[0003] In the power system, methods such as second harmonic content and waveform symmetry are generally used to identify the inrush current at the moment of switching on, but with the increase of transformer capacity and the improvement of manufacturing process, the differential error In addition, during operation, due to the influence of the inrush current, the current protection function in the line protection fails to correctly identify the inrush current, which leads to the wrong judgment of the relay protection as the fault current and the malfunction occurs from time to time.

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