Transient overvoltages (SPD)

Transient overvoltages are surges that can reach tens of kilovolts with a duration of the order of microseconds.


Despite their short duration, the high energy content can cause serious problems to equipment connected to the line, from premature aging to destruction, causing disruptions to service and financial loss.

This type of surge can have various different causes, including atmospheric lightning directly striking the external protection (lightning rods) on a building or transmission line or the associated induction of electromagnetic fields on metallic conductors. Outdoor and longer lines are the most exposed to these fields, which often receive high levels of induction. It is also common for non-weather phenomena, such as transformer centre switching or the disconnection of motors or other inductive loads to cause voltage spikes in adjacent lines.

Transient overvoltages do not occur solely in power distribution lines, but are also common in any line formed by metal conductors, such as telephony, communications, measurement and data.

In all these networks, transient overvoltage protection is achieved by installing the protector or line discharger on the vulnerable line, connecting it in parallel between the line and earth. This means that in the event of a transient overvoltage, the protector will discharge excess energy to earth, thus limiting the peak voltage to a value acceptable for the electrical equipment connected.







Go to General operation and selecting a protector

Go to Protection parameters according to IEC 61643-1

Go to Protection parameters according to UL 1449 3rd Ed

Go to Installation of a Surge Protector

Back to Surge protection

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