Wind Farm Grounding 1

[Blackberry77]

Hi,

I am doing a grounding study for a wind farm. The turbine areas have high resistivity layers (granite) and it is hard to obtain low step and touch potentials and GPR.

The system is as follows:

YY autotransformer with a buried delta
several mile long overhead collector line of ACSR with 5 turbines tapping off
OPGW interconnecting all ground grids back to the substation grid

I have modelled this in CDEGS considering the current I get from ETAP at each location. Is it advisable to use FCDIST for current splitting and how would I model this situation? Also, what methods could I employ to lower the step, touch, and GPR without driving ground wells. If I were to drive ground wells, how do I model this in CDEGS. I only have the MultigroundZ package.

Much thanks!

 

[waross]

Google Ufer grounds. See Wiki
I consider Herbert G Ufer one of the unsung pioneers of our industry.

During World War II, the U.S. Army required a grounding system for bomb storage vaults near Tucson and Flagstaff, Arizona. Conventional grounding systems did not work well in this location since the desert terrain had no water table and very little rainfall. The extremely dry soil conditions would have required hundreds of feet of rods to be driven into the earth to create a low impedance ground to protect the buildings from lightning strikes.

In 1942, Herbert G. Ufer was a consultant working for the U.S. Army. Ufer was given the task of finding a lower cost and more practical alternative to traditional copper rod grounds for these dry locations. Ufer discovered that concrete had better conductivity than most types of soil. Ufer then developed a grounding scheme based on encasing the grounding conductors in concrete. This method proved to be very effective, and was implemented throughout the Arizona test site.

Link to Wiki

Bill
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"Why not the best?"
Jimmy Carter