surge

A surge protector, spike suppressor, surge suppressor, surge diverter, surge protection device (SPD), transient voltage suppressor (TVS) or transient voltage surge suppressor (TVSS) is an appliance or device intended to protect electrical devices in alternating current (AC) circuits from voltage spikes with very short duration measured in microseconds, which can arise from a variety of causes including lightning strikes in the vicinity.
A surge protector limits the voltage supplied to the electrical devices to a certain threshold by short-circuiting current to ground or absorbing the spike when a transient occurs, thus avoiding damage to the devices connected to it.
Key specifications that characterize this device are the clamping voltage, or the transient voltage at which the device starts functioning, the joule rating, a measure of how much energy can be absorbed per surge, and the response time.

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