Editing Varistor (section)

== Limitations ==
A MOV inside a transient voltage [[surge suppressor]] (TVSS) does not provide complete protection for electrical equipment.  In particular, it provides no protection from sustained over-voltages that may result in damage to that equipment as well as to the protector device.  Other sustained and harmful over-voltages may be lower and therefore ignored by a MOV device.

A varistor provides no equipment protection from [[inrush current]] surges (during equipment startup), from [[overcurrent]] (created by a short circuit), or from [[voltage sag]]s ([[Brownout (electricity)|brownout]]s); it neither senses nor affects such events. Susceptibility of electronic equipment to these other electric power disturbances is defined by other aspects of the system design, either inside the equipment itself or externally by means such as a UPS, a voltage regulator or a [[surge protector]] with built-in overvoltage protection (which typically consists of a voltage-sensing circuit and a relay for disconnecting the AC input when the voltage reaches a danger threshold).