Low frequency transport measurements have been performed on GdSr ₂ RuCu ₂ O ₈ pellets. The current-voltage curves measured show an irreversible behavior in whole range of temperature explored. From these curve a Curie temperature T_cM=133 K and a superconducting critical temperature T_cS = 14 K , with an onset temperature T_cO=33 K , have been deduced. A simple phenomenological model assuming a non-linear inductance in series with a resistance has been proposed to explain experimental current-voltage curves. Within this model, the temperature dependence of some physical quantities has been also investigated.