Substation Fence Energization
Substation Fence Energization
(OP)
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.






RE: Substation Fence Energization
As far as touch voltages and step voltages are concerned this 6V is nothing. What I will do is to lay some insulating
gavel up to 1m away from the fence. Can it be a transferred potential from somewhere else?
RE: Substation Fence Energization
RE: Substation Fence Energization
Therefore, there are limits as to how much touch potential there may be (and step potential). Has any calculations or measurements been carried out? Most countries do not allow operation of plants where the touch potential is too high.
When you say "remote earth point" - how remote? And is it measured with an equivalent "human body" load or with a DMM with 10 megohm input impedance?
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Substation Fence Energization
RE: Substation Fence Energization
In your case, initial voltage of 6-10V referred to remote point is meaningless, since the real dangerous overvoltage will happen under short circuit conditions of the nearby power line or at the substation. Now, how many times someone will touch the fence during the short circuit nearby, is something IEC did a study, so you might use this study to demonstrate that IEC is saying that the probability of occurrence of short-circuit event is very low, and someone touching the fence at the exact same moment which last 1-5s at most is even lower. That is if authority accept IEC.
Much as I know, no other software can help you calculate the induced voltages under this condition. Doing it manually is possible, but maybe too complicated?
Provision of 1m of gravel beyond the fence line and proper grounding/earthing of the fence and fence doors are a must, using IEEE or IEC. That is also the minimum of standard, everything else is extra, including detailed calculation with CDEGS.
I hope this will help.
Regards
RE: Substation Fence Energization
The fence earthing is a subjective issue and cannot be generalised. Depending on what facility is fenced? Is it an industrail facility, A comercial establishment or a vegitable farm in the remote area or a junk yard? What is the transmission voltage etc.
If the fence is having a stray voltage, install a couple of earth rods, form an earth grid and connect the fence to the earth grid at no. of points. This should be good enough to hold the fence at earth potential.
RE: Substation Fence Energization
Skogsgurra raises some good questions. How was this measured? Has anyone complained about getting shocked? I think more data is needed. I have used the software referenced above (SES CDEGS software) to calculate similar voltages under steady state conditions. Since you reference a transmission line, I'm assuming you have a long metallic fence running parallel with some transmission lines, which is leading to induction issues? I'm just guessing here, but that problem can be addressed fairly easily with good bonding. Without any more information it's hard to make any recommendations, but I wouldn't just throw some rock around the fence without getting a better understading of the problem. My first instinct is that it's not an issue with not having enough insulation, it's an issue of not enough bonding.
RE: Substation Fence Energization
RE: Substation Fence Energization
I'm not so sure this is valid. As two unrelated events, maybe. But I can construct some scenarios where work inside a substation goes terribly wrong and the instinctive reaction of the crew is to run for the gate.
Actually, I've been on site when something like this happened (everyone survived uninjured).