Impulsive interference has been measured recently in some wireless communication environments. By using measured data of partial discharge, we show in this paper that the Middleton Class A model can approximate the impulsive noise in an electricity substation better than the Gaussian noise. The measured data was obtained from Hydro-Quebec's Research Institute in cooperation with ETS (Ecole de technologie superieure of Montreal). We derive an extension of Middleton Class A model for multi-antenna systems. Using this model with estimated parameters from measured data, we evaluate the performance of two linear MIMO precoders with two spectral efficiencies (4 bit/s/Hz and 8 bit/s/Hz). The max-dmin precoder optimizes the minimum Euclidean distance of the received constellation and the max-SNR or single beamforming maximizes the received SNR.