This paper presents a new quadrupole model of the mean temperature rise in the transient hot strip (THS) method dedicated to the measurement of thermal conductivity of thin films. It takes into account the following aspects often neglected in the previous works: the thermal impedance of the heater, the convective heat transfer, the anisotropy of the thin film as well as the thermal contact resistances. It also considers the variation of the heating power while keeping the current constant. A sensitivity study highlights the influence of these parameters on the hot strip mean temperature. A study on the limits of the simplified model used for thermal conductivity estimation is presented. The error resulting from considering a constant heating power as generally done is estimated. The mean temperature rise calculated with the quadrupole model deviates by less than 1% compared to the numerical simulation performed with COMSOL.