Study On Characteristics, Prediction And Control Technique Of UHV Transformer Substation Noise

In this study,domestic and abroad researches related to characteristics of low-frequency noise,main sources and control measures of transformer substation noise were reviewed.Based on these researches,noises of a typical 1000kV transformer substation were sampled by field test and time-frequency characteristics of UHV transformer substation noise were analyzed.Moreover,differences among results of UHV transformer substation noise predicted and calculated by three kinds of softwares including Cadna/A,SoundPLAN and Virtual.Lab were analysed and verified by comparing with field test data.Noise reduction effects of various typical control measures aiming at reducing UHV transformer substation noise were analyzed quantitatively by Virtual.Lab,then several control measures were recommended through optimal comparasion of relevant parameters.Economic analysis of their engineering costs were also carried out.At last,by the method of subjective evaluation experiments,sound adjustment and control measures probably improving subjective perception of UHV transformer substation noise were further studied.Results of this study are shown as following.(1)There are a series of tonal components at 100Hz and its harmonic frequencies in noise from high voltage reactors of the UHV transformer substation.However,A-weighted octave band sound power spectrum of noise from main transformers is smoother than that from high voltage reactors because of the masking effect of cooling fan noise.Besides,the non-weighted sound energy ratio of low-frequency component in noises from both main transformers and high voltage reactors are more than 98%.(2)There are some differences among UHV transformer substation noise prediction results calculated by three kinds of softwares including Cadna/A,SoundPLAN and Virtual.Lab under the same setting of prediction parameters.Cadna/A and SoundPLAN are considered to be more suitable to predict the influence of UHV transformer substation noise to the acoustic environment outside the station.However,Virtual.Lab is more suitable to predict the noise influence in the near field region of main transformer.Due to sound interference of noises between each phase of high voltage reactor,none of the three softwares are suitable to predict the noise influence in the near field region of high voltage reactor.(3)When taking sound interference into consideration by Virtual.Lab,the prediction accuracy cannot be improved obviously because of the simplification of interference sources in the prediction model.(4)If the sound power level of main transformer reduces by 20dBA and that of high voltage reactor reduces by 12dBA using measures of noise source reduction,noises outside both the south and the north boundaries of the transformer substation will meet noise emission limits of the 2nd class sound environment functional area in the "Emission standard for industrial enterprises noise at boundary"(GB 12348-2008).Futher noise reduction measures should be taken towards low voltage reactors to make noises outside both the east and the west boundaries to meet the standard.(5)Setting sound barriers on two sides of main transformers and high voltage reactors can effectively reduce the influence of UHV transformer substation noise(noise reduction at boundaries is 1.9dBA-3.9dBA).The barriers should be as high as the existing firewalls and have a high absorption coefficience at low frequency.Noise reduction of sound barriers with strong sound absorption treatment is at most 2.6dBA higher than that without any sound absorption treatment.(6)Sound adjustment measures,such as adding water flowing sounds of suitable intensity and less low-frequency component on UHV transformer substation noise or reducing its sound pressure level at 100Hz,can improve subjective perception of UHV transformer substation noise effectively.Results of this study are of great significance to scientifically understand the influence and targetedly control the pollution of UHV transformer substation noise.Meanwhile,they can also provide technical support for the construction of UHV transformer substations in China from the perspective of environmental protection.