surge

A surge protector (or spike suppressor, surge suppressor, surge diverter, surge protection device (SPD) or transient voltage surge suppressor (TVSS) is an appliance or device intended to protect electrical devices in alternating current (AC) circuits from voltage spikes, which can arise from a variety of causes including lightning strikes in the vicinity and have a very short duration measured in microseconds.
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 appliances and 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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