Earthing / Grounding : Hot Zone Contour covers residential properties

[sotoneng68]

I am currently facing some problems designing the earthing of a HV substation. Although I have experience designing earthing on several other projects in rural areas this is the first one that I have encountered in an urban area.

The site suffers from incredibly high soil resistivity and the hot zone contour covers several residential properties.
I am uncertain as to what precautions need to be taken at the properties covered by the hot zone. I am aware that work will most likely be required on the phone lines to the house but I am uncertain about the water pipes and power supply.

My concern is that potential will be transferred to other properties oust side the zone of influence either through metal water pipes or through the earth / neutral conductor of the power supply.

Precautions such as inserting insulating sections to pipes leaving the properties and altering their earthing systems seems rather costly to me. Personally I find it hard to believe that such precautions are necessary as I know of hot substations in the center of cities where such precautions would have an astronomical cost attached.
I have found it very hard to discover any information on this either in the standards or in text books. Does anyone have any experience with this problem? What precautions would be necessary? I would be really grateful for some advice as this project is becoming quite urgent.

Many thanks

 

[7anoter4]

The water pipe has to be of insulating material made-high density polyethylene or other-OSHA permissible. The grounding conductor has to be grounded at service side as per NEC Art.250.The neutral conductor has to be well insulated at consumer side. Usually the supply system from a substation is underground medium voltage cable and a NER [Neutral Earth Resistance] or other voltage limiter could reduce the transferred potential [See-IEEE 575ch.6].

 

[MKFPE]

Google this paper:
" SAFETY ISSUES RELATED TO THE CONNECTION OF MV AND HV GROUNDING SYSTEMS OUTSIDE SUBSTATIONS. Y. Rajotte. J. Fortin. G. Lessard. "
I will soon be working on a project with a similar issue and plan to use WinIGS software for analysis.
Using Google Earth one can find many substations in both rural and metropolitan areas with adjacent residences.
The ones with swimming pools really makes one wonder.

http://www.sptimes.com/2004/08/24/news_pf/Northpinellas/Crews_solve_puzzle_of.shtml

So you are right to be concerned about the issue since the use of adjacent properties is not under your control.

 

[MKFPE]

Sorry, that was not the paper I intended to refer to in my earlier post.

Try "EARTH POTENTIAL RISE INFLUENCE NEAR HV SUBSTATIONS IN RURAL AREAS" Authors: Rajotte De Sève Fortin Lehoux Simard

and

"A TOUCH VOLTAGE MEASUREMENT METHOD APPLICABLE ON ENERGIZED MV AND LV LINES" Authors: Rajotte Fortin Cyr

The authors are with Hydro-Québec

 

[karls2]

Do you try to take in account the split factor for reduce the value of the current trough the earth grid ?
In some case it can help you especially if you are in a case of cable instead line for the incomer.