| The power transformer is one of the main noise sources in converter station, so great attention has been gradually paid to its influences on the social environment. Studying on experimental measurement methods of power transformer will improve the measuring accuracy of the sound pressure level and sound power level, which is very significant for the noise evaluation and the subsequent noise controlling.There are three kinds of calculation methods for environmental correction in power transformer noise measurement. After analysis and comparison of the factors affecting the precision of each method, the results are as follows:according to computational accuracy of environmental correction, the precision of standard source method is higher than that of the approximate method and the reverberation method. When reverb effect is more noticeable in test room, in other words, the average acoustic absorption coefficient is less than0.2, the precision of the reverberation method is superior to the approximation method.According to noise measurement of a single-phase AC transformer (two windings) in Guangdong power equipment testing center and the analysis of the influence of measuring area (with/without the top surface area) on the sound power level, the result is as follows:excluding top surface area, the calculated value of the sound power level is smaller than the actual value. The conclusion is consistent with the result of theoretical analysis.Through studying the theory of bridge balance and electrical characteristics of the transformer, an acoustical noise measuring circuit of transformer was designed. The circuit’s function is to ensure that power frequency voltage and harmonic frequency voltage do not interfere with each other when they are loaded simultaneously, which is confirmed by the MATLAB/Simulink simulation analysis. According to the characteristics of the loading harmonic frequency and some correlative noise measurement standards, an acoustical noise measuring method was finally given to the situation when power frequency voltage and harmonic frequency voltage were loaded simultaneously. |
