High Voltage Lattice Tower Earthing

[Deansharafi]

Dear all,

Do you know of any useful information or literature in relation to high voltage tower earthing, concept, design criteria, testing and commissioning etc.

Thanks

 

[mc5w]

As far as grounding goes, one of the members of this forum works for a Colorado electrical utility and says that on the portions of their system that use 17 foot ( about 5.5 meter ) ground rods they have ZERO lightning damage. This is done using ground rod couplings. There are both threaded couplings that use factory threaded rods and threadless couplings for ordinary copper clad steel rods.

Any kind of rebar in the bottom of a new building in the U.S. is now a mandantory grounding electrode. This type of ground, known as a Ufer ground, was first used in Arizona to deal with dry sandy soil and rocky soil. This was shown to be an excellent ground even in a desert. If your tower foundation goes down at least 10 feet and the rebars are bonded to the J-bolts you should get a good ground. If the tower is built on solid rock a good ground is more difficult but substantial surface area between reinforced concrete and the rock helps. In the case of solid rock you may need to run ground radial wires with backfill that will retain salt water and periodically dose with salt water.

You can also get a cheap soil boring from 2 companies, 1 named Borit and the other Borzit and you can use this tool to sink 1.25 inch or 1.5 inch type L or better copper tubing 20 feet into the ground if the soil will allow it.

John Labriola, who is one of the top electrical inspectors in northeast Ohio says that when you drive an 8 foot ground rod from the surface only the bottom 2 feet act as a grounding electrode. When he worked as an electrical contractor he liked to drive the ground rod underneath the basement floor before the basement floor was poured. This would take as much advantage of natural soil moisture as the top of the rod is already 6 or 7 feet below surrounding terrain.