AbstractThis paper presents a topologically based theoretical background for designing tests for identification of faulty parameter values in linear subnetworks. Nodal voltages are assumed t o be obtainable either by measurements or, indirectly, as a result of a nodal fault analysis. A formulation of nodal fault analysis for subnetworks is presented. It is shown how this approach can be used to evaluate faulty elements within inaccessible faulty subnetworks. The objective of this work is the reduction of the number of required current excitations and, thereby, the number of voltage measurements. The Coates flow‐graph representation of a network is use