Power transformer winding turn-to-turn short circuit failure detecting method based on resistance frequency curve

Abstract

The invention discloses a power transformer winding turn-to-turn short circuit failure detecting method based on a resistance frequency curve. The method comprises the steps that all the non-tested windings of a detected power transformer are made to be in a short circuit; the frequency sweeping signals of the preset frequency and amplitude are linearly applied to the head end of a detected winding, meanwhile, voltage signals on non-inductive resistors connected at the head end and the tail end of the detected winding are measured, and per unit values of the impedance of the detected winding under different frequencies are calculated through a computational formula; the trend curve of the impedance per unit values, changing along with the frequency, of the detected winding is drawn according to all the impedance per unit values obtained under the preset frequency, the trend curve is compared with a historical trend curve, and whether the winding turn-to-turn short circuit failure exists or not is detected according to the comparative result. The power transformer winding turn-to-turn short circuit failure detecting method based on the resistance frequency curve can overcome the defects that in the prior art, measuring difficulty is large, the accuracy degree is low and the misjudgment rate is high so as to achieve the advantages of being small in measuring difficulty, high in accuracy degree and low in misjudgment rate.

Description

technical field [0001] The invention relates to the technical field of fault diagnosis and state evaluation of power equipment, in particular to a detection method for inter-turn short-circuit faults of power transformer windings based on frequency-resistance curves. Background technique [0002] Among the various equipment in the power system, the power transformer is a relatively expensive and very important pivotal equipment, and its operation reliability is directly related to the safety and stability of the entire power system. Under normal circumstances, the electromagnetic stress of the transformer is not large, but when a short-circuit fault occurs, especially a short-circuit fault in the near area (usually including three types of faults: transformer outlet short circuit, internal lead short circuit and phase-to-phase short circuit or winding-to-ground short circuit), the low voltage of the transformer There will be a large short-circuit current on the side, and the...

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Problems solved by technology

[0008] To sum up, scholars at home and abroad have done a lot of research on the diagnosis method of inter-turn short circuit fault of transformer winding. It is difficult to make a correct judgment on the inter-turn insulation state of the winding

Although the criterion of the short-circuit reactance method is clear, it is very susceptible to electromagnetic interference in the substation because it uses a power frequency 50Hz signal for excitation, which affects the accuracy of the measurement; method, sometimes even if the inter-turn short circuit fault has occurred in the winding, the correlation coefficient may not change significantly because the correlation coefficient compares the similarity of the two curves, resulting in misjudgment

[0009] In the process of realizing the present invention, the inventor found that there are at least defects such as difficult measurement, low accuracy and high misjudgment rate in the prior art

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