Grounding Design with Very High GPR
Grounding Design with Very High GPR
(OP)
Hello
I am handling the design of a substation limit whose grounding design is with with very high GPR, while Step and touch are within limits. The normal practice is to use conductor and rods.
What possible method is to bring GPR close to the acceptable limit.
Can I use remote contribution less than 100%.
The surface thickness more than 1.5m.
The asphalt surface resistivity more than 3000 ohm m?
The number of outgoing feeders more than 1 and distribution feeders as per actual?
The utilization of GEM in extremly dry rocky area?
The available area is 50x50 m and top layer is having resistivity more than 1000 ohm m.
Please guide me in this regard.
Asad
I am handling the design of a substation limit whose grounding design is with with very high GPR, while Step and touch are within limits. The normal practice is to use conductor and rods.
What possible method is to bring GPR close to the acceptable limit.
Can I use remote contribution less than 100%.
The surface thickness more than 1.5m.
The asphalt surface resistivity more than 3000 ohm m?
The number of outgoing feeders more than 1 and distribution feeders as per actual?
The utilization of GEM in extremly dry rocky area?
The available area is 50x50 m and top layer is having resistivity more than 1000 ohm m.
Please guide me in this regard.
Asad






RE: Grounding Design with Very High GPR
You can use remote contribution less than 100% only if it is less than 100%. Is part of the ground fault source local?
Adding surface thickness or asphalt will increase allowable step- and touch-potential but will not lower GPR.
Outgoing feeders with grounded neutrals will reduce the amount of current flowing into the grid and the GPR. Some of the fault current will flow through the neutrals and return to the source through the neutral grounds. If the resistivity is high, this may cause touch-potential problems at the distribution feeder ground points (transferred potential).
Using GEM can reduce GPR.
RE: Grounding Design with Very High GPR
However, if you intend to reduce the GPR you have to reduce the grounding resistance.
You may try the soil treatment with material like this one:
http://www.saraswateng.com/TEREC_Data%20Sheet.pdf
RE: Grounding Design with Very High GPR
Check also if any other cables are bonded to the grid.Communcation cables may need to be isolated in the substation to avoid transferred potential.
very important to check if this substation is within an inhabited neighbourhood,also, check communication cables are not interfering with GPR of 430 V and 650 V contours as per IEEE 80.
This article should give you an idea about risks.
https://en.wikipedia.org/wiki/Earth_potential_rise
RE: Grounding Design with Very High GPR
Is GEM a reliable method in dry rocky area?
RE: Grounding Design with Very High GPR