Earthing lightning arrester

[vandax]

Dear friends,
please advice regarding method of earthing LA at distribution line. In our current practice 13.8 kV line with using pipe pole, the LA is always earthed to gound via pole (brazed), but our new study shown that the earthing of LA must be via a special wire to reduce impact of surge impedance at pole.

Is it realistic??

 

[Macnee]

To earth the LA via a separate conductor is not only realistic but also adivisable. the LA should be effectively earthed to ensure its function Actually our practice in small substations is to provide a separate earthpit.. but on line earth cable with proper earth & min resi. is OK

 

[dpc]

It is realistic. A surge event or lightning strike can be visualized as a massive build-up of electrons trying to get to ground in a big hurry. If they have a direct, low-impedance path, this is where the bulk of the current will flow. If the path is high impedance or has a lot of bends and convolutions, the current will find additional pathways.

This surge current has high frequency components and the added inductance of a steel conductor will present a high impedance.

 

[vandax]

Thanks friends.

Actually our pole design is using pipe pole, and static wire is barecooper 35 mm.

If we consider that the impedance of barecooper is lower than pipe, this method is okey, otherwise...

 

[dpc]

Yes, but how does the static wire get to the earth? You will want a direct copper connection to earth at each pole for the best protection.

 

[vandax]

I mean that the bare cooper (same wire for static) is used to connect the bottom of LA to ground.

For certain pole, we also ground the static in order to get lower system impedance.

 

[busbar]

2f4n, if you haven't done so, you may want to look over 'Subscribe To Forums' and 'Personal Profile' links in the upper lefthand corner of most of the Eng-Tips pages. It's kind of a busy place.