An MOV can experience degradation caused by constant AC/DC line voltage stresses, lightning, switching transients, temporary overvoltage (TOV), leakage-caused watt-loss heating that can eventually kill the MOV, or increasing leakage current with surge history, time, and temperature. Over time, damage to the MOV’s internal structure can lead to a thermal runaway condition that effectively ends the life of the component. In many cases, end-of-life events can result in undesirable conditions such as fire and fragmentation of the MOV.