In order to reduce time out of the transformer circuit, implementation of methods for online monitoring is important. Using electromagnetic waves has recently been proposed for on-line monitoring of the transformer. In this paper, a new analytical method based on locus of objects in space to detect the radial deformation of winding, is proposed. The proposed experimental set-up for this method has been modelled using CST (Computer Simulation Technology) software. The simulation results show that exact determination of radial deformation location along the transformer winding height can be detected with good accuracy using this method.