Establishment Method of Correction Factors for Noise Level Prediction about 500 kV Combined Transformers Based on Field Measurement Analysis

Prediction of substation boundary noise Levels is one of the essential steps in the design phase of newly planned substations. However, the boundary noise level values calculated by superimposing the no-load sound pressure levels derived from delivery test and the simulated load sound pressure levels are generally lower than the actual measured boundary noise levels after the substation is put into operation. This prevents designers from selecting transformers with lower noise levels or accurately adding noise reduction measures such as BOX-IN and sound barriers during the design phase, thereby inducing the risk of excessively high boundary noise levels after the substation is commissioned. To improve the prediction accuracy of boundary noise levels for 500 kV substations, based on the sound pressure level measurements of 165 in-service 500 kV assembled transformers across 31 500 kV substations, the analysis of the impact of load levels and fans operation status on transformer sound pressure levels was completed. Compared with field measurements, the correction coefficients for transformer sound pressure levels under fan-off and fan-on conditions were established and verified, providing a data-driven correction approach to improve the prediction accuracy of boundary noise levels in 500 kV substations.