Hi there, if the from bus-from has a rated voltage level of 230 kV and the to-bus of 115 kV (or vice-versa) the tap (ratio) of the transformer is 1, because the transformer ratio equals the ratio of the defined rated voltage levels of the buses. At least one of r or rather x shouldn't be 0, usually r!=0 and x!=0.
e.g.: - Bus 1: 110 kV as a rated voltage level - Bus 2: 20 kV as a rated voltage level - Transformer from Bus 1 to Bus 2 with ur=1%, uk=10%, S=32 MVA and a nominal ratio of 115 kV to 21 kV - S_base = 100 MVA (used and defined in Matpower by myself) tap or ratio = (U1n / U2n) / (U1r / U2r) = (115/21) / (110/20) = 0.9957 r = ur * S_base / S_Trafo = 0.01 * 100/32 = 0.03125 p.u. x = sqrt(uk^2 - ur^2) * S_base / S_Trafo = sqrt(0.1^2 - 0.01^2) * 100/32 = 0.31 p.u. Kind regards, Chris Am 30.12.2016 um 20:31 schrieb Angel Pastor: > > Dear MATPOWER community. > > > Greetings and happy holidays to everyone, i have some doubts about the > representation of the transformers, for those branches with > transformers i put the transformation relationship betwen the voltages > in the "from bus" and the "to bus" in the column TAP (number 9 column) > of the branches matrix. > > > In my case i have transformers of (230/115)kV, so the value i'm > writting in the column TAP is 2, but, according to what i read this is > valid only when r=x=0... Wich is not my case, because i have r=0 and > x=0.075... So how can i calculate the value that should go in TAP to > represent the transformer correctly? Should i put the performance value? > > > Thank's from advance. >
