A reusable nonlinear polymeric composite varistor composed of a linear low density polyethylene (LLDPE) as the matrix and doped zinc oxide varistor powders as the functional fillers, sintered at 850, 950 and 1100 degrees C for 5 h, is used as a novel material to limit excess voltage, current or power. The functional fillers act as varistors due to their grain boundary characteristics which can be adjusted by different formula and sintering conditions. When applied field is above breakdown field of the filler the current density increases abrupt if a critical temperature is reached. Thereby the over voltage is limited by fillers (i.e. varistor effect) and the over current is limited by polymer matrix (i.e. PTC effect). We studied the dependence of the E-J characteristics on the preparation conditions of filler material, the filler content in the polymeric matrix and suggest possible nonlinear electrical-thermal switching mechanism.