i have been working on 220/132KV 160 MVA auto-Transformer in 220 KV Grid station and i have observed that under no Load it makes huge noise as compared to under loaded condition why ??
i believe the issue is related to the mechanical vibration, try to mount the transformer on a rubber base. moreover check the fixation of the coil and bolts if exist on its structure
Hello,
Well, usually the noise of transformers, and auto-transformers increases with the increase in loading level. In your case, the situation is reversed as you noticed higher noise level at no load conditions in comparison with loading conditions. This phenomenon may be attributed to high no-load harmonic currents, which occur due to the nonlinear relation between the flux density and the magnetic field strength of the core. Due to aging and frequent stresses, the no-load harmonic currents increases. As a result, the magneto-striction of the core increases due to increased separation of the laminated layers of the core. You may read
https://testguy.net/content/259-Transformer-Humming-Noise-Explained
Article Factors that influence transformer no-load current harmonics
Please share possible information about the age of the mentioned auto-transformer, its adopted maintenance scheme, and the history of normal and abnormal stresses. In addition, please mention the history of the detection of the no-load noise problem.
Thank You all for Your Help ..... Yes i agree with Mohamed EL-Shimy . one of the factor is aging too since its been 25 years that Auto-Transformer is working and , according to surge arrestors readings installed on HV and LV more than 30 surges has struck the transfomer so far.
You are welcome. The state of the auto-transformer, as you described, is a clue evidence of aging degradation. Probably, this transformer suffer from the end-of-life symptoms. The failure rate, and the rate of change of the failure rate may be used to correctly indicate the operating life phase of the transformer.
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