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An Introduction to UK Surge Protection

Surges or Transient Overvoltages

Surges or transients are short duration increases voltage measured between two or more conductors. These potentially harmful voltages can be induced into a building from a direct strike of from secondary effects of lightning which can reach up to 6000 Volts.

Type of UK surge protection unit or SPD

In order to protect equipment, you need to select SDP units that can deal with these effects.

A Type 1 SPD will deal with a direct strike.

A Type 2 and 3 SPD will deal with the indirect effects or locally generated surges, such as switching events. A combination of these (co-ordinated SPDs) can provide full protection to protect equipment within a building.

Low let-through Voltage

An effective SPD should have a low let-through voltage as this is the amount of voltage the equipment being protected will be subjected to. The greater the over voltage the greater the risk of disruption, degradation and damage to equipment connected to the electrical system. As technology moves on, components within electronic equipment continue to become smaller and therefore more sensitive to these types of influence.


As a general guide, all cables that enter or leave a building should be protected as these lines offer electricity pathways in.

Most buildings will have at least one main power supply and a copper telephone line. Power protection and telephone protection should be applied at the main distribution board and main telephone line jack or main distribution point.

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