Hi GroovyGuy: My concern is for a homeowner that lives adjacent to a substation with the substation fence built right on top of his property line. Not only do we not have the opportunity to extend the apron of the ground grid 3 feet beyond the fence to negate an outer touch potential at the...
In reference to the GPR voltage gradients around a substation during a close-in fault and the extreme drop-off point at the edge of the station ground grid, is there a possible touch (not step) potential hazard if a metal stake was planted into the ground within say 10 feet away from the fence...
Are there standards (IEEE, NESC) that require the need for an express (implying insulated) connection between the neutral bus in a switchgear and the Xo bushing of the transformer? There are thoughts that simply connecting the switchgear neutral bus which may be carrying 100 amps or more of...
To pwrtran- The split factor has been inclusive already and still the Touch potential fails at the fence.
To JG2828- Your thoughts about using AMICO non-conductive fencing is fantastic! This brochure showing it already installed at a substation is a convincing element to use it. Some of my...
To crany108: The substation is about 50 years old and built when the entire world did not have the design tools we now have to understand that you generally need a three foot ground conductor outside the fence to mitigate touch potentials. A wall would make the neighbors backyard resemble a...
I cannot pass IEEE80 touch potential criteria at a substation fence built on top of the property line adjacent to neighbors. I cannot move the fence inward three feet in order to get a horizontal ground conductor three feet out from it as this restricts our ability to get to the substation...
Our substation has a security fence (encloses all substation equipment) and a separate perimeter fence (around the edge of the property line). Both fences are separately grounded with the security fence ground tied to the substation ground grid. I am using WinIGS to evaluate the touch and step...
Are there any national codes or standards that say substation fences cannot be energized? We have some fences near transmission lines that have an induced voltage of between 6 and 12 volts when measured from a remote earth point.
To cranky108- great idea with the asphalt. IEEE80 even states that asphalt is 10,000 ohm-meters at its worst (wet). One thing we need to make sure of is the drainage of rain water. Thanks for the answer.
To bacon4life- We will certainly look into what "fractured rock" is vs spalls. How do...
To Zanoter4- preparing a truck route and then restoring it is time consuming and restoring the rock after usage tends to mix dirt with the rock when re-using it. This problem is quite common is many of our substations. Thanks for the suggestion anyway.
To PHovnanian- using smaller rock will...
Our substation rock is sized 3/4 to 1-1/2 (years ago it was larger) and some of the heavier utility trucks have a tendency to sink their wheels into the rock making traction difficult. Our normal depth is between 4 and 5 inched. Any ideas or suggestions?
IEEE80(2000) has Sf current split factors shown on page 153 for a Dist gnd of 25 ohms vs one for 200 ohms. The table on page 151 line 4 from the bottom says R=.322 and X=.242 for 25 ohms and then R=1.65 and X=.291 for 200 ohms (the far right column heading is wrong and should say Rdg=200).
If I...
We are empirically testing substation rock spalls for resistivity and come up with around 10,000 ohm-meters of resistivity. The IEEE80 uses a typical example of 2500 to 3000 ohm-meters for substation rock resistivity. Are we way off base? Our samples are 1-1/2" drain rock.
When going thru the Travis-Pattern Bus support catalog, some slip fitting supports will include the Static Eliminator springs if an "SE" is suffixed on the part number. They are supposed to push the bus up against the walls of the ring type support to eliminate chatter/vibrations and minimize...
To jghrist: Yes, we did a high side fault analysis with the 5 X 5 ft mesh for a grid under the tower site and all passed. Our grid mesh at the substation is 15 X 15 ft and using a 15 X 15 ft mesh under the cell tower failed the touch potential at the cell site area only; the substation passed...
