Transformer direct-current magnetic bias judgment method based on vibration signal processing

Abstract

The invention discloses a transformer direct-current magnetic bias judgment method based on vibration signal processing. The method comprises the following steps of firstly, judging whether the ratiok1 of the energy sum of frequency components, except 100 Hz frequency components, of a transformer vibration signal to the energy of the 100 Hz frequency components is greater than delta1 or not, andif not, determining that the transformer is in a normal working state, if yes, recording the abnormal starting moment t1, continuously judging whether k1 in the deltat time window after t1 is greaterthan delta1 or not, and if not, determining that the transformer has a short-circuit fault or is struck by lightning, if yes, whether the ratio k2 of the sum of the 50 Hz frequency component energy and the 150 Hz frequency component energy of the vibration signal to the 100Hz frequency component energy is larger than delta2 or not is judged continuously, if not, judging harmonic interference of the transformer occurs, and if yes, judging direct-current magnetic bias occurs to the transformer. The method can achieve accurate and reliable recognition of the direct-current magnetic bias of the transformer under the condition of eliminating three types of abnormal conditions: a short-circuit fault, lightning stroke and harmonic interference.

Description

technical field [0001] The invention relates to a transformer DC bias judgment method based on vibration signal processing, and belongs to the technical field of transformer vibration signal detection and processing. Background technique [0002] During the operation of urban rail transit, unipolar operation of HVDC power transmission system or geomagnetic storm, DC current will flow into the neutral point of the transformer, resulting in distortion of transformer excitation current, resulting in DC bias phenomenon, manifested as increased vibration and local Overheating will endanger the safe and stable operation of the transformer and even the power supply system. Therefore, it is necessary to detect the DC bias of the transformer, so as to take relevant measures to prevent the DC bias from causing harm to the transformer. [0003] In the prior art, there is a means to detect the transformer DC bias by monitoring the neutral point current of the transformer. The method f...

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Problems solved by technology

[0003] In the prior art, there is a means to detect the transformer DC bias by monitoring the neutral point current of the transformer. The method for judging the DC bias in a coupling transformer and a 750kV autotransformer all judges the DC bias of the transformer by collecting the DC current at the neutral point of the transformer. There is abnormal vibration in the iron core, and the neutral point DC current cannot directly reflect the change of the excitation current or the vibration of the transformer. Therefore, it is necessary to detect the DC bias of the transformer from the perspective of transformer excitation current monitoring or transformer vibration monitoring.

[0004] In terms of obtaining the transformer excitation current, there are also some reports in the relevant literature. The Chinese patent application number 2015103125304 proposes a transformer excitation current simulation method based on the J-A hysteresis model. Simulation and Experimental Research on Excitation Current (Bai Baodong, Zhao Xiaoxuan, etc., Journal of Electrotechnical Society, 2013, S2)” proposed an experimental method for transformer excitation current based on the J-A model, and the Chinese patent application number 2016108556946 proposed a UHV transformer The real-time calculation method of no-load DC bias excitation current, but the above research can only obtain the excitation current of the transformer under the condition of DC bias during the no-load experiment, and it is still not possible to obtain the excitation current of the transformer in the actual project online, that is, it cannot Real-time detection of the DC bias of the transformer in operation

[0005] There are also DC bias detection methods based on transformer vibration signals in the existing technology. For example, the Chinese patent application number 201110432033X proposes a method for discriminating DC bias magnetism of power transformers based on vibration analysis. It mainly uses the collected transformer vibration The signal is embedded into the m-dimensional space by delay to obtain the corresponding digital symbol sequence, and the corresponding characteristic function is constructed through the sequence histogram, and then the DC bias is judged according to the characteristic quantity, but the proposed method does not consider the instantaneous impact (such as short-circuit fault , lightning strike) to the judgment method, and did not distinguish between harmonic interference and DC bias, that is, did not consider the influence of harmonic interference on DC bias discrimination. Therefore, it is necessary to propose a method that considers short-circuit faults, lightning strikes, and harmonic interference Judgment Method of Affected Transformer DC Bias

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