Thank You. That was my mistake.
OK. All variables of time must be either a state variable or input, but after entering
StateSpaceModel[Join[components, kirchhoff],
{Subscript[u, C][t], Subscript[u, R][t], i[t]}, Subscript[u, in][t], Subscript[u, R][t], t]
I have
StateSpaceModel::invrlzn: The system of equations {Subscript[u, C]^\==i/C,Subscript[u, R]==R i,Subscript[u, in]==Subscript[u, C]+Subscript[u, R]} with outputs {Subscript[u, R]} does not possess a state-space realization.
google, but nothing. please, help!