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.
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 buildings||0,75|
|Isolated on a hill or promontory||2|
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.