LV surge protection installation

It’s Good to have in mind practical aspects: case of a low voltage  switchboard To achieve the effective installation of the surge protection, the surge arrester’s connections to the grid should be as short as possible. Any cable crossed by a lightning impulse current has a significant voltage to be added to the Surge Protection Device (SPD) residual voltage.

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nice picture from

Practical example (figure 1):

A copper cable with a length L1 + L2 + L3 = 1 meter crossed by a lightning impulse current = 10 kA during 10 microseconds has roughly 1000V between its two ends. This voltage is added at the SPD protection level and its protective device (eg 1800V) so this is 2800V that “sees” the sensitive electrical equipment

In this case, the sensitive equipment is destroyed because its voltage withstand shocks does not exceed 2500V.

example : figure 1

example : figure 1

The solution consists in reducing the length of the cables like this (Figure 2):

L1 reduction: connect the surge protection device close to the electrical power network terminal block

L2 reduction: install the protective device over the surge arrester. The most effective solution is to use a surge arrester with an integrated short circuit protection device (L2 = 0)

L3 reduction: Install an intermediate earthing terminal as close as possible to the SPD earth terminal block, then connect the main earthing protection cable from the ground directly to this intermediate earthing terminal, then connect an other cable between the intermediate earthing terminal and the SPD earth terminal block and finally connect the intermediate earthing terminal to the main earthing terminal.


example : figure 2

Didier Mignardot


  • We produce various surge protectors for AC/DC/signal system of analog/digital/RF, and we are looking for distributors and agency overseas, if you are interested, please feel free contact me by “”.

    • please e-mail yr product info – do u have any company dealing with yr products in Malaysia ?.

      • Dear CS,

        Sorry I just came back here and found your reply posting. Could you send me an email at xyu (at) szdowin (dot) com? Our product features MOV & GDT. Once I have your email, will respond quickly.


        Rhett Yu

    • hi rhett am from india name is sameer, we are interested in your distribution ship we currently are in contracting as well as dealerships if you are interested send me a mail at “”

  • plz do help me abt this installation of surge protection as i need it for my clg project.

    • Please describe in detail wher u want to install a surge device.
      Normallly they are installed acrosse potential lines.

      Please specify more


  • plz can you help me to found many information on this topic becouse it is my final year project as we know our country is very poor and the library is not confortable for using so plz help mee.

  • unavailable resource for Technical Books especially power transmission line (caculation software, construction, protection sytsem…) that why pushing me to find these books for students like me.
    we want them!

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