Method for recognizing inrush current of transformer based on waveform modulation

Abstract

The invention provides a method for recognizing an inrush current of a transformer based on waveform modulation, and the method comprises the steps: 1, calculating a differential current and a brakingcurrent of the transformer; 2, modulating the differential current; 3, recognizing the inrush current of the transformer. The method achieves the discrimination of a magnetizing inrush current and aninternal fault current of the transformer through the calculation of the pulse period of the modulated differential current, and can be used for the research of the differential protection technologyof the transformer. The method can achieve the quick collection and calculation of the longitudinal differential currents of various types of transformers, and achieves the inrush current recognitionwhen the differential currents exceed a preset value. The method achieves the discrimination of the magnetizing inrush current and the internal fault current of the transformer through the calculation of the pulse period of the modulated differential current. The differential protection operation of the transformer can be sped up if necessary, thereby generating favorable influences on a power transmission and transformation system.

Description

technical field [0001] The invention belongs to the technical field of electric power system relay protection, and in particular relates to a transformer surge current identification method based on waveform modulation. Background technique [0002] The identification of transformer short-circuit current and inrush current is the key to the correct operation of transformer differential protection. At present, the typical identification methods for inrush current include the principle of second harmonic, the principle of discontinuous angle and the principle based on waveform symmetry. Because the residual magnetism of the transformer is high or the second harmonic content may be less when the closing angle meets certain conditions, the traditional second harmonic braking principle is challenged. The discontinuous angle principle criterion uses the discontinuous characteristics of the inrush current. Its essence is to use the mathematical morphology gradient transformation an...

AI Technical Summary

Problems solved by technology

The discontinuous angle principle criterion uses the discontinuous characteristics of the inrush current. Its essence is to use the mathematical morphology gradient transformation and wavelet singularity detection to detect the singularity of the discontinuous angle. However, when the current transformer is saturated under the airdrop, the waveform will appear Distortion, difficult calculation of discontinuity angle, affect the reliability of the criterion

Based on the principle of waveform symmetry, using the characteristics of positive and negative half-wave symmetry of the fault waveform, using related algorithms such as the integral of the positive and negative half-wave sampled values ​​or the integral of the ratio, which essentially reflects the sum of the contents of each even harmonic, and the space There are also issues with the reliability of throwing phase-by-phase braking

In addition, there are magnetic flux characteristic method, equivalent instantaneous excitation inductance method, etc. These methods manually set the transformer parameters, and the calculation process is relatively complicated, which affects the practical application.

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