GROUNDING SYSTEM CONDUCTOR
GROUNDING SYSTEM CONDUCTOR
(OP)
THe grounding system design is made of rings of conductor that is earthed to several earthing rods. The rings or loops are surrounding specific areas.
The soil resitivity is low. The choice has earthing conductor has been chosen as insulated rather than bare due to the corrosive affects of the soil.
Is this acceptable? All metallic parts are connected to teh earth rings.
The soil resitivity is low. The choice has earthing conductor has been chosen as insulated rather than bare due to the corrosive affects of the soil.
Is this acceptable? All metallic parts are connected to teh earth rings.






RE: GROUNDING SYSTEM CONDUCTOR
What keeps the rods from corroding? How do you keep the conductor to rod connection from corroding? How do you seal the conductor at connections to keep moisture out?
RE: GROUNDING SYSTEM CONDUCTOR
You might also need electrolytic corrosion protectionbut you would need quite a bit of direct current to protect ground rods. Pipelines that use electrolytic corrosion protection are insulated on the outside both to concentrate the electric field at the surface ( where it is needed the most ) and so that any current only needs to protect cracks and chinks in the insulation. Otherwise, you would need a power supply every few hundred yards which is not economical.
RE: GROUNDING SYSTEM CONDUCTOR
Is is acceptable considering touch and step voltages to choose an insulated ground conductor to act as the ring around equipment and buildings?
I see lots of references that it is acceptable to use bare or insulated grounding conductor but is it accepatble to use insulated conductor for the main ring system, even this will be connected to ground rods.
RE: GROUNDING SYSTEM CONDUCTOR
RE: GROUNDING SYSTEM CONDUCTOR
RE: GROUNDING SYSTEM CONDUCTOR
If the allowable potential is greater than the actual voltage rise in the event of a fault then the design with insulated cable may be acceptable. Otherwise, a bare conductor may be required to reduce dangerous potential rise.
The soil resistivity is low....
Standing In low resistivity native soil, the allowable potentials are also low. This could be improved with a few inches of high resistivity material such as crushed rock.
The choice has earthing conductor has been chosen as insulated rather than bare due to the corrosive affects of the soil.
One practical way to mitigate the corrosive effect of soil is oversizing the bare ground conductor in such a way that the reduction of the net section of the bare conductor at the end of the life time of the project is at least the minimum section to preclude fusion of the cable in the event of a short circuit. Bare conductor 4/0 is used satisfactorily in many grounding installation.
The enclose figure show the shape of the voltage distribution in the vicinity of the grounded surface with buried bare conductor or without buried conductor (or insulated cable).
I hope this could help.
RE: GROUNDING SYSTEM CONDUCTOR
Thanks for your feedback.
You provide a calculation for step and touch voltages. How do calculate the allowable step and touch voltages as i have understood that 50V was theh limit.
Are you aware of any installations where thay have successfully used insulated conductors?
RE: GROUNDING SYSTEM CONDUCTOR
Enclose is a sample of allowable step and touch potential calculation:
http://cuky2000.250free.com/Step.pdf
QUESTION 2:...as i have understood that 50V was the limit.
As far as I remember, there are not specified limits in the ANSSI/IEEE Std 80 for the allowable step and touch potentials in the ANSI/IEEE Std 80. However, there is limit for metal-to-metal touch voltage varying from 150V to 60 V for 0.5sec to 4 sec. respectively (refer to fig 15 IEEE std 80 -2000)
NOTES:
1- The total allowable voltage as calculated per the ANSI/IEEE Std 80 is larger than allowable voltage through the human body since this calculation include voltage drop in the standard shoes and upper soil resistance under worst case wet conditions.
2- I understand that the Canadian and European Standards limits the step and touch potential as follow:
a- Canadian Code:
• 3143 volts step voltage for a ½-second fault and 2216 volts for a 1-second fault; and
• 885 volts touch voltage for a ½-second fault and 626 volts for a 1-second fault
b- Germany: (DIN VDE 0100 ):
Touch voltage limit values under persistent fault: 50 V ac & 120 Vdc
QUESTION 3: Are you aware of any installations where successfully used insulated conductors?
I used insulated conductor to tie two substations for one special requirement. This was totally different scenario than the case you are describing. Personally, I do not see any advantage using insulated conductor in your case.