Determination of optimal transformer noise levels in outdoor substations using pseudo-inverse

Transformers in outdoor substations often need to comply with strict noise regulation standards in urban areas. In this paper the authors propose a practical method for determining the acoustic noise levels of transformers to be reduced in an urban outdoor substation. The proposed algorithm is based on a pseudo-inverse calculation using an empirical formula for noise levels at the boundary points around the substation premises. Necessary input parameters are three dimensions of each transformer and distance between transformers and each boundary point. By solving the pseudo-inverse problem of the linear system, the sum of transformer noise levels that is achievable by minimum upgrade cost is determined. The proposed method is demonstrated on a model substation and a real primary substation. Solutions were also compared with an optimal solution obtained by linear programming that minimizes the sum of transformer noise level reductions with the minimum cost.