How long does a transient surge protector last?

21 April, 2022

The estimated lifetime or life expectancy of transient surge protective devices is determined by the maximum discharge current Imax, which indicates the durability of the transient surge arrester.

It should be taken into account that the surge absorption capacity of the surge arrester is cumulative, so it is not necessary to change it after each discharge as if it were a fuse. The protector gradually “wears out” as it receives these discharges.

cuanto dura un protector de sobretensiones torres

How do I calculate the life expectancy of a transient surge arrester?

The estimated life expectancy of transient surge arresters is determined by the formula:

Life expectancy = Imax/ (Am × Ng)


  • Am = area of lightning incidence on buildings
  • Ng = lightning density per km2 per year

Let us take, for example, an isolated building in Cáceres for which we assume an area of lightning incidence on buildings (Am) equal to 1 (see table below), and a lightning density per km2 per year (Ng), obtained from the map below, equal to 1.5.

Incidence of lightning strikes on Am

Close to other buildings or trees in the
same height or higher
Surrounded by lower buildings0,75
Isolated on a hill or promontory2
Source: Technical Building Code (CTE) – SU8 (Safety against lightning)
cuanto dura un protector de sobretensiones mapa2
Illustration: Map of impact density on terrain N
Source: Technical Building Code (CTE) SU8 (Lightning Safety)

Practical example of transient surge arrester lifetime calculation

If the Vigivolt V2T-15 equipment is installed, with an Imax of 15kA and adding the above data, we use all the variables to perform the following calculation.

Life expectancy =Imax / (Am × Ng) = 15/(1 × 1.5) = 10 years

In other words, an Imax 15kA surge protector installed in a building of these characteristics in this area will be capable of receiving impacts for approximately 10 years.

Obviously this is an approximate calculation, since the density of lightning per km2 per year is not fixed, but varies according to the year. We make the calculation with the map provided in the Technical Building Code (CTE) SU8.

If you need another type of transient surge protector, you can consult more equipment in OUR TRANSITORY SURGE PROTECTORS CATALOGUE.

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