Calculation & Test of a 110 kV Power Transformer No-load Noise and Its Radiation Characteristics

Abstract

No-load noise caused by magnetostriction of core is the main component of power transformer noise. Because the complexity of the vibration mechanism, it is difficult to be calculated and analyzed accurately. And there is a lack of software for no-load noise simulation. The fitting formula is commonly used in engineering application to estimate the noise, which is usually quite different from the measured noise level. The calculation method of transformer no-load noise is studied in this paper. Considering the magnetization and magnetostriction anisotropy of silicon steel sheet, a magneto-mechanical coupling model is established. Taking the magnetization and magnetostriction characteristics of silicon steel sheet as the coupling medium, the magnetostriction force of the core of a 110kV power transformer is calculated, and its no-load noise is simulated and analyzed, using finite element method. Results show that the main frequency of magnetostriction force is 100Hz, and at the same time there exist components of force at 200Hz and 300Hz. No-load noise test of transformer is carried out and the test data are compared with the simulation. Results show that the difference between the simulation and the test is very small at the main frequency of transformer no-load noise, which verifies the validity of the calculation method. The reasons for the error between the test and simulation are also analyzed. On this basis, the radiation characteristics of no-load noise are further analyzed, and the control methods of transformer no-load noise are discussed. It shows that the no-load noise of the transformer has obvious spatial distribution differences, and the contribution of each tank wall and cover to the noise is also different. Thus, measures can be taken to realize the control of the no-load noise of the transformer based on the results of radiation characteristics analysis.