I'm trying to understand the effects of having a transformer connected to a branch on the implicated admittance matrix. In the MatPower manual, section 3.2, equation 3.2 describes such a relation for a 2x2 branch admittance matrix.
I'm interested in the general form of the (diagonal and off-diagonal) elements of an admittance matrix, when multiple branches have transformers attached. Particularly the diagonal elements are confusing, how are the elements summed up, if multiple have transformers? Further, in the test case files, the absence of a transformer is indicated with its ratio and angle set to 0. In the mentioned equation (3.2) that would cause problems when dividing with 0. So another question is how are those elements treated in the light of formula 3.2? Thanks a lot.
