Surge / Ground / Lightning
in [Home Built PC]
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From: w_tom on 6 May 2008 02:47 Nobody described how much more earthing is installed in switching centers (COs), electric substations, etc just to obtain a little better earthing. A ten foot earth ground rod can be a massive earthing improvement for surge protection. And then high reliability facilities may spend $thousands more just to make that earthing but a little better. Why so much extra conductors and labor for just a little better ground? Because every little better earthing means that much more surge protection. What makes a protector even more effective? Better earthing. So yes, where surge damage is not acceptable, then facilities will do that much more work just to get a little better earthing. Earthing is critical for direct lightning strikes without failure. Does that mean a homeowner without a massive earthing mat should do nothing? Of course not. Locating 3 meter ground rods (per post 1990 NEC requirements) less than 10 feet from breaker box and telco provided surge protector means significantly better protection. Anyone building a new home should plan their surge protection where footings are poured - see nobody's reference to cadwelding. Footings with appropriately installed conductors (rebar) provide a home with significant improvement (Ufer grounds). Protection should be planned when the footings are poured. Better earthing (surge protection) for so little money. Nobody also discusses single point earth ground that is essential for surge protection. Why? Again, a protector is only as effective as its earth ground. Single point earth ground is essential to an effective protector. Some homeowners don't have that single point option due to failures by the builder. One utility describes how to fix that defective earthing: http://www.cinergy.com/surge/ttip08.htm Why do serious facilities do so much for their earthing system? Earthing provides surge protection - where surge energy must be harmlessly dissipated. And then, as Nobody notes, sometimes that earthing system gets compromised by geology we did not know about. What happens if damage occurs? We return to locate an earthing defect. Even a nearby pipeline may adversely affect that earthing system. If damage results, then discover a defect in the earthing system. As Nobody demonstrates, so much labor to make earthing even better because a surge protector is only as effective as that earth ground. BTW, battery racks do not absorb surge energy. Another concept even taught in basic circuit theory - superposition. To surges, that battery rack is equivalent to a short circuit. Batteries do not absorb energy (if ignoring a battery's internal resistance). Those batteries essentially connect surge currents to wires on both sides of those batteries. To a surge, batteries are electrically equivalent to a wire. Batteries are typically well earthed - meaning those batteries will act just like a shunt mode surge protector - connecting surge energy into earth. Batteries don't work as surge absorbers. Batteries connect (shunt, divert, clamp) surge energy into earth. On May 5, 6:31 pm, "nobody >" <usenetharves...(a)aol.com> wrote: > I've been a TV repairman. I'm now a "communications electrician" which > means I deal with telephone lines/switches, land-mobile radio, microwave > radio systems, security systems, and the like; in high-voltage > switchyards and substations. We deal with huge surges from switching > transients and direct lightning hits on the transmission lines. I know > first-hand what happens when surges hit. When I said "transmission > lines", I'm talking both from the 60hz side as well as the RF side as > the lengths are sufficient to act that way. > > Define "ground" or "earth", Mr w_tom. Have you ever run an ANSI spec > ohms test on one? I think not. I've done grounding for military tactical > radio systems and complete commo systems. What you think is "ground" may > not be ground at all due to soil composition. I've seen ground rod > "farms" made up of 20+ vertical 8' rods on a 10 foot grid come up in the > 500 kilohms range when the same rods in the same location would test > lower than 1000 ohms if those same stakes were buried sideways 18" below > surface. > > Substations/switchyards have "ground mats" of heavy copper wire in a > grid spacing of 1-2 feet and about 6 feet under everything that's > covered with gravel. It's also cad-welded at all intersections to > prevent corrosion. This ground mat system is also used at well-designed > radio sites. Even with this elaborate grounding system, a major > malfunction at 230KV can create such a voltage differential to induce > fatal "step voltage" between your legs. >.http://ballengearry.com.au/papers/Step_and_Touch_Voltage_update_for_2... > > For 120Vac grounding on our equipment, we try our best to bring all > equipment grounds (racks and cable trays as well) to a single point that > *then* connects to the building's ground as close as possible. We do > have the advantage of most equipment running off DC at 24, 48, or 130 > Vdc on huge battery racks that can absorb a lot of surge energy...
From: Mike Tomlinson on 6 May 2008 02:38 In article <ercv14losi2mbapd8k5bmirr77vffj6mkn(a)4ax.com>, spamfree(a)spam.heaven writes >I was going to ask whether this would help protect delicate components >in any way, Yes, as the surge protector is working to some extent, but it would work far more effectively if it were plugged into a grounded outlet. There's also the problem that using a surge protector in an ungrounded outlet will cause the earth on the protector to rise in potential while the protector is conducting a surge. Depending on the equipment plugged into that strip, this has the potential to cause damage, as well as an electrical shock to anyone touching a metal-cased appliance with a 3-pin lead plugged into the strip. Thus surge protectors should only be plugged into grounded outlets. There will usually be a warning on the protector itself or in the user instructions stating this. > but of course, the neutral is earthed nearby anyways, and >the third earth wire is just a backstop? No. The earth pin, although bonded to neutral at the consumer unit (=breaker box in US) should be regarded as a separate, third connection from then on. The neutral is there to carry return current; the earth is there for safety. -- (\__/) Bunny says NO to Windows Vista! (='.'=) http://www.cs.auckland.ac.nz/~pgut001/pubs/vista_cost.html (")_(") http://www.cypherpunks.to/~peter/vista.pdf
From: w_tom on 6 May 2008 02:53 On May 5, 2:35 pm, bud-- <remove.budn...(a)isp.com> wrote: > The IEEE guide is aimed at "electricians, architects, technicians, and > electrical engineers who were not protection specialists." IEEE and NIST state fundamental facts. Industry standard facts and embarrassing questions.that Bud will ignore to lie and to promote plug- in protector sales: 1) How does that plug-in protector provide protection without the 'always necessary' earth ground? What does a protector do? Bud provides only two citations. Both disagree with his claims. The NIST bluntly defines what a protector must do - Page 6: > You cannot really suppress a surge altogether, nor > "arrest" it. What these protective devices do is > neither suppress nor arrest a surge, but simply > divert it to ground, where it can do no harm. Bud says his plug-in protectors somehow suppress or arrest surges. Somehow, 'clamping to nothing' means that surge energy disappears? Somehow protectors can work without earthing? NIST citation further contradicts Bud on Page 17: > A very important point to keep in mind is that your > surge protector will work by diverting the surges to > ground. The best surge protection in the world can > be useless if grounding is not done properly. 2) Bud not only denies this also so important single point earth ground. He also ignores what happens when a protector is too far from earth and too close to appliances. Page 42 Figure 8: the surge earthed 8000 volts destructively through appliances. This is the second point from his citations that Bud must ignore. 3) So if a plug-in protector is effective protection, then manufacturer specs will list each type of surge and protection from that surge. Bud never provides that spec either. Why? Plug-in protectors don't claim to protect from the type of surge that typically causes damage. Not one plug-in protector manufacturer will claim that protection - made obvious because Bud will not post those specs and ignored over 400 requests for those specs. 4) No earth ground means no effective protection. A protector is only as effective as its earth ground. Another reality that Bud must ignore to post incessantly. None of this is new. It is again posted because Bud continuously ignores that even his own citations contradict him. Meanwhile w_tom has provided many tens of professional citations that also contradict Bud; that define how effective protection is routinely installed where direct lightning strikes must not cause damage. We install effective protection for lightning so that all other (and lesser) surges are also made irrelevant. Surge protection is so routine for the past 100 years as to be traceable to human failure. Even the protector must remain functional after a surge.
From: w_tom on 6 May 2008 03:02 On May 5, 2:19 pm, Mike Tomlinson <m...(a)jasper.org.uk> wrote: > On properly grounded outlets, such a suppressor can deal with an > incoming surge on phase or neutral in an effective manner by conducting > and diverting current to the other leg AND to ground, but their > effectiveness when used on ungrounded outlets is reduced, since the path > to ground doesn't exist. Include facts taught in first year electrical engineering OR described in both 'top of the front page' articled in Electrical Engineering Times on 1 Oct and 8 Oct 2007 entitled "Protecting Electrical Devices from Lightning Transients" at: http://www.planetanalog.com/showArticle.jhtml?articleID=201807127 http://www.planetanalog.com/showArticle.jhtml?articleID=201807830 That wire from wall receptacle is too long, has too many sharp bends, has spliced, is bundled with other wires, etc. More reasons why that safety ground wire is not earth ground wire. Protectors without earth ground is not effective as Mike says. And AC wall receptacle does not provide an earthing connection - wire too long - too much impedance. Page 42 Figure 8 also demonstrates that problem resulting in 8000 volts being earthing, instead, through the adjacent TV. Breaker box earthing wire goes over top of the foundation and drops down to an earthing electrode. Compromised protection. Wire is too long and has sharp bends. Better protection means wire goes through foundation and down to that earthing electrode. Few meters less wire and without those sharp bends means improved protection. Why? See "Protecting Electrical Devices from Lightning Transients". If earthng wire must be every meter shorter, then how does a receptacle safety ground wire do earthing? Safety wire has maybe 30 or 50 sharp bends, numerous splices, and maybe 15 meters too long? Low impedance connection to earth typically means 'less than 10 feet', or then even shorter for even better protection. Obviously wall receptacle safety grounds do not provide earth ground. But then Mike Tomlinson also did not understand the engineering numbers in that EE Times article entitled "Protecting Electrical Devices from Lightning Transients". Note the numbers. Wall receptacle safety grounds cannot provide a low impedance connection to earth ground. Engineers would know this. Mike Tomlinson obviously does not. Literally every incoming wire must make that short (low impedance) connection to earth ground. If that earthing wire is not separated from other wires (if that earthing wire is inside a bundle of romex cables), then that earthing wire induces surges on those other wires. Just another reason why safety ground is not earth ground. Just another engineering fact that Mike Tomlinson read and did not understand. AC wall receptable is not an effective earth ground. Protectors best make a less than 3 meter (low impedance) connection to earth which wall receptacles just cannot provide.
From: w_tom on 6 May 2008 03:06
On May 5, 2:27 pm, Mike Tomlinson <m...(a)jasper.org.uk> wrote: > It is those nuances that w_twat fails to explain when he spouts his one- > cure-for-all-ills religious mantra about every dwelling absolutely > requiring whole-house surge protection. Mike Tomlinson has just posted in agreement. UK homes typically do not need what is necessary in FL homes. UK homes need not be earthed as central FL homes may be earthed: http://members.aol.com/gfretwell/ufer.jpg Many homes have more than enough protection with only one earthed 'whole house' protector - and nothing else. Especially in the UK. That means spending tens (or maybe one hundred) times less money for protection of everything. UK homes may be more than sufficiently earthed with one 3 meter ground rod. Then one surge protector can provide more than sufficient protection for everything - eliminating maybe £500 or £2000 for plug- in protectors. |