on the left hand side of the equation is singular since it satisfies where is an column matrix containing only 1s. This corresponds to the fact of current conservation, namely, , and the freedom to choose a reference node (ground). In practice, the voltage at the reference node is taken to be 0. Consider it is the last node, . In this case, it is straightforward to verify that the resulting equations for the other nodes remain the same, and therefore one can simply discard the last column as well as the last line of the matrix equation. This procedure results in a dimensional non-singular matrix equation with the definitions of all the elements stay unchanged. See also Mesh analysis Ybus matrix Topology (electrical circuits) Charge conservation Circuit diagram References P. Dimo Nodal Analysis of Power Systems Abacus Press Kent 1975 External links Branch current method Online four-node problem solver Simple Nodal Analysis Example Electronic circuits Electrical engineering