Transformer Differential Protection Method Based on Two-Dimensional Space Reconstruction of Current Characteristic Trajectory

Abstract

A transformer differential protection method based on two-dimensional spatial reconstruction of the current characteristic trajectory, at a certain sampling frequency, the current sequence I measured by the current transformer TA on both sides of the transformer is collected 1 and I 2 , in a periodic data window, the number of sampling points is N, I 1 ={I 1 (1), I 1 (2),...,I 1 (i),...,I 1 (N)}, I 2 ={I 2 (1), I 2 (2),...,I 2 (i),...,I 2 (N)}, the two sets of current sequences I will be collected 1 and I 2 Reconstruct the trajectory in the two-dimensional coordinate system to form a reconstructed trajectory sequence L, L={L(1),L(2),...,L(i),...,L(N)}, i=1,2 ,...,N. Calculate the percentage K of the number of points in the reconstructed trajectory sequence L that fall into the first and third quadrants of the two-dimensional coordinate system to the total. Combine the calculated K value with K set Compare, where K set It is the setting value of protection action, if K>K set , then it is judged as a fault in the zone, and the protection action; if K <kset is determined as an out-of-area fault, and the protection is blocked. In this method, the current information on both sides is used to reconstruct the characteristic trajectory in the two-dimensional coordinate system, and the quadrant characteristics of the trajectory under different fault types are quantitatively analyzed to identify the fault type accompanied by TA saturation.< / k

Description

technical field [0001] The invention relates to a transformer differential protection method based on two-dimensional spatial reconstruction of a current characteristic trajectory, and relates to the technical field of transformer differential protection. Background technique [0002] Transformer is an important equipment in power system transmission, the correctness of its protection action is particularly important. For a long time, transformer differential protection has been widely used as the main protection of transformers because of its simple principle and only using current to distinguish fault types. Whether the transformer differential protection can operate correctly depends on whether the TAs on both sides can correctly transmit current information. When one side of TA is saturated, the wrong current information transmitted by it will cause abnormal operation of differential protection. [0003] At present, the ratio braking method, second harmonic braking met...

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Problems solved by technology

These methods have achieved good results in identifying TA saturation and improving the performance of differential protection, but there are still some shortcomings: using the ratio braking method, the protection will be affected if the braking coefficient is too high or too low; The precise positioning of the fault moment and the moment of differential current occurrence is difficult to achieve, so the reliability cannot be guaranteed; the second harmonic braking method may delay the action due to the occurrence of a large number of harmonic components; the wavelet method is to detect the extremely large secondary current of TA However, there will be large deviations at some critical points or zero-crossing points; the criterion provided by the morphological method requires a lot of calculation time and may delay the protection action; the virtual braking current method needs to be combined with other criteria

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