ABSTRACT The bus impedance algorithm was originally developed in 1960 by Brown, Person, Kirchmayer and Stagg [l], viewing the elements of the bus impedance matrix as open circuit parameters of the network. In this paper an alternative formulation based on simple matrix algebra is presented. Only well established simple results of network matrices are used For any change in the partial network, first, the bus admittance matrix is derived. Then, with proper matrix inversion technique, the corresponding bus impedance matrix is obtained. The development is comprehensive so as to include the effects of mutual couplings, multi line switching, phase shifting components etc.