Power transformer load tap changer switching contact slap fault diagnosis method and device

Abstract

The invention relates to a power transformer load tap changer switching contact slap fault diagnosis method and device. The diagnosis method includes that: firstly, real-time monitoring is carried outon tap changer switching action process, in the monitored signal, the latter half of time domain signal major energy is selected, so as to avoid the energy maximum point in time domain signal; secondly, time-frequency transformation analysis is carried out; thirdly, spectral line of the signal, which is higher in amplitude at the range of 800-1000Hz in frequency domain, is determined through analysis; fourthly, comparing is carried out, if the spectral line is obviously amplified compared with the normal condition of the tap changer, the tap changer is in the switching contact slap fault. Theinvention has the advantages that: the found fault characteristic value can accurately reflect tap changer switching contact slap fault, characteristic is obvious, repeatability is good, and the method has universality on tap changers of the same type; the load tap changer contact slap fault diagnosis technology is simple in engineering realization, and a sensor is convenient in installation; anda microcomputer is adopted for detection, processing and diagnosis, performance is reliable, realization is convenient, and diagnosis conclusion is visual.

Description

technical field [0001] The invention relates to a method and a device for diagnosing loose faults of switching contacts of an on-load tap changer of a power transformer, belonging to the field of electrical control engineering. Background technique [0002] The condition-based maintenance strategy based on online monitoring and fault diagnosis technology will become an inevitable trend of future development. The on-load tap changer is a very important power transmission and transformation equipment in the power system. It can not only stabilize the load center voltage, but also is an indispensable important equipment for connecting the power grid, adjusting the load flow, and improving reactive power distribution. It has been used in the power grid Wide range of applications. [0003] At present, a large number of transformers of 110kV and above are installed with On-Load TapChanger (OLTC), whose function is to complete transformer voltage regulation under load. The operat...

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Problems solved by technology

The other group of contacts is seriously overloaded and overheated. If it is not discovered in time, the contacts of the tap changer will be burned quickly, making the entire switch and transformer unable to work.

In addition, after the contacts are loose, the switching contacts are in poor contact during the switching process, causing serious arcs, and it is easy to burn the switching contacts

[0005] At present, there is no reliable diagnostic method for tap changer faults. The research methods mainly include methods based on gas analysis in oil (such as the three-ratio method), monitoring and analysis methods based on vibration, and diagnostic methods based on thermal noise.

However, due to the normal operation of the tap changer, the corresponding gas will also be generated in the oil due to the opening and closing of the contacts. Therefore, the analysis method based on the gas in the oil is currently difficult to achieve; the diagnosis based on thermal noise is due to the transformer split The thermal noise generated by the heat generated after the breakout switch is transmitted to the outside of the transformer, and the tap changer fault diagnosis is carried out by installing a noise sensor on the transformer shell for detection. This is based on the fact that the tap changer contacts have obvious faults and have generated serious heat ( Slight heat will not produce obvious thermal noise), on the other hand, thermal noise propagates to the outside of the transformer, the energy loss of the signal is large, and various interferences are added, which is difficult to achieve in engineering (there are many kinds of noise in the transformer operating environment, especially electromagnetic The noise and background noise are very large, which are much greater than the energy of the signal transmitted to the outside of the transformer oil tank due to overheating due to loose contact faults); there are many factors that cause vibration during the switching process of the tap changer, especially when the trigger of the tap changer is in motion. The vibration of the tap changer is very large, which brings difficulties to the vibration analysis. Therefore, the key to the vibration-based tap changer fault diagnosis is to find the characteristic signal that can reflect the fault in the monitored signal. In addition, the monitoring method and the post-monitoring signal analysis method also affect the analysis. The accuracy of the fault diagnosis of the switch

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