The scattering parameters can be powerful description of interconnect parameters. In the paper we present the closed form formulas for the scattering parameters for low loss interconnect. The method bases on multiple scales method and expands the voltage and current in series of losses parameter. The first order approximation calculate the lossless line response. The impact of losses is included in constants of solution of differential equation. The proposed formulas for scattering parameters are compared with exact calculations in frequency domain.