Surge / Ground / Lightning
in [Home Built PC]
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From: Mike Tomlinson on 5 May 2008 14:27 In article <481f4eb2$0$31762$4c368faf(a)roadrunner.com>, Timothy Daniels <SpamBucket(a)NoSpamPlease.biz> writes > Does that mean a combination of w_tom's "whole house protection" >and individual "surge protectors" at those "critical devices"? That's >what I've always felt would be prudent - not a single method of >protection, but a combination. Yes, but the environment in which the protected dwelling is situated should also be taken into account. For example, a house in Florida, with its overhead power lines and frequent thunderstorms, would be a more likely candidate for a combined approach to surge protection. On the other hand, installing Florida-levels of protection in a house in the UK with its infrequent storms, reliable underground power supply and a decent electrical system with properly earthed sockets, would be a waste of money. It is those nuances that w_twat fails to explain when he spouts his one- cure-for-all-ills religious mantra about every dwelling absolutely requiring whole-house surge protection. Like another poster to this thread has said, things are never black and white, but shades of grey. The sensible approach is to evaluate the risk and install an appropriate level of protection. -- (\__/) Bunny says NO to Windows Vista! (='.'=) http://www.cs.auckland.ac.nz/~pgut001/pubs/vista_cost.html (")_(") http://www.cypherpunks.to/~peter/vista.pdf
From: bud-- on 5 May 2008 14:45 Don Kelly wrote: > ---------------------------- > "Tony Hwang" <dragon40(a)shaw.ca> wrote in message > news:dncTj.112858$rd2.31639(a)pd7urf3no... >> phil-news-nospam(a)ipal.net wrote: >>> In alt.tv.tech.hdtv Michael A. Terrell <mike.terrell(a)earthlink.net> >>> wrote: >>> >>> | Bullshit. Like ALL charges, it simply seeks a complete circuit to >>> | flow. You have absolutely no grasp of the basic concepts, yet you >>> | continue to spout your ignorance and lies. >>> >>> Not true. >>> >>> When you close a switch between a power source and a pair of wires that >>> go >>> out yonder, the electrical energy does not "know" whether the circuit is >>> complete or not. If it refused to flow, it would not be able to find >>> out. >>> It will flow, whether the circuit is complete or not. What happens after >>> that depends on what is at the other end, which could be an open >>> condition, >>> a short circuit, or some kind of resistive or reactive load. >>> >>> You've claimed to have worked in broadcasting in an engineering role. So >>> you should understand what happens at the end of an open transmission >>> line. >>> The electricity flows to get to the open end. Yet it is not a "complete >>> circuit". >>> >> Hmmm, >> You seem to be confused between current flow(energy) and voltage(poential) >> Nothing flows in an open circuit. If not we have to rewrite Ohm's law. >> Show your credential to make a stamement like that. >> Shameful. > ------------------------ > Actually, you are showing some confusion. Phil is right in that he is > bringing out a point that normal lumped RLC circuit theory doesn't handle > because it essentially treats the speed of propagation of electrical signals > as if it were infinite- which isn't true. > . > 2)Also, on energizing a line whether it is open or closed, there is a > current flow as the applied voltage "sees" the characteristic impedance of > the line (wire or whatever) so a current will flow-even on an open circuit- > until there is a modifying reflection from the termination. For a house the > distances are such that this may be of the order of 0.1-0.2 microsecond. > After all such reflections at terminations have ceased or are negligable, > conventional circuit theory is applicable. > In these situations, you are dealing with wave propagation rather than > conventional circuit theory. > This is the regime that is of interest in considering "surge protectors" The last standards for simulating typical surge waveforms I have seen (IEEE) were 1.2 us rise time, 50 us duration 8 us rise time, 20 us duration a ring wave with a frequency about 100kHz. All are long relative to 0.2 microsecond, so wave propagation should not be relevant for household circuits. A favorite article from w_ also uses a "8x20 us impulse as a very rough representative pulse" with most harmonic content from 20kHz to 100kHz. Martzloff, using the shorter rise time, has written: "For a 1.2/50 us impulse, this means that the line must be at least 200 m long before one can think in terms of classical transmission line behavior." What reason is there to believe wave propagation is relevant to house circuits? > > As to the advantage of "whole house" vs local surge protection, "whole house > protection depends on distances to all "protected" items being small. Longer distances make the system more subject to effects like direct induction from lightning into the wiring. I don't see why, in general, the distance has to be small. -- bud--
From: phil-news-nospam on 5 May 2008 14:36 In alt.engineering.electrical Jitt <tser827(a)yahoo.com> wrote: | In article <74683977-6a03-4695-a5a2- | 156ba3653409(a)m45g2000hsb.googlegroups.com>, w_tom1(a)usa.net | says... |> On May 3, 4:38?am, Franc Zabkar <fzab...(a)iinternode.on.net> wrote: |> > Can you elaborate on this by showing us the path taken by the strike |> > through the TV? |> |> Path to earth was through the network and into a third computer. |> Through that third computer's motherboard, through modem, and to earth |> via phone lines. Semiconductors in these paths were damaged. |> |> We literally traced this path by replacing ICs. Some ICs (ie |> network interface chips) even had cracks on packages where surge |> current entered or exiting those ICs. Absolutely no doubt as to how |> surge currents found earth ground, destructively, via adjacent |> computers. |> | I wonder why, since electrical codes in North America | and Britain require a ground connection at each outlet; | computer power cords are 3 wire? What good is having the ground connection at each outlet if it is not used? Are British power cords for computers only 2 wire? 2 of the wires are power conductors. Usually one of the is grounded somewhere back along the path to the power system source. But it is possible for one to have a connection with two hot wires (208V from three phase or 240V from single phase in North America ... 400V from three phase in Europe ... I doubt any of those 230/460 single phase systems are around anymore in Britain). The 3rd wire is the groundING conductor. It is not supposed to carry any current except in the case of a fault between a hot wire and the case or frame of the computer (or whatever appliance is involved). While this is a rare event, it is a more important protection in the case of appliances that routinely get handled by people more than just being turned on and off. An electric table lamp might not need the grounding conductor because of the infrequent handling just to turn it on and off. A computer or cooker would be handled more than a lamp. A computer would be subject to more handling than the cooker, but the cooker would be subject to being wet. Both of them are in far more need of the grounding protection than the lamp. -- |WARNING: Due to extreme spam, I no longer see any articles originating from | | Google Groups. If you want your postings to be seen by more readers | | you will need to find a different place to post on Usenet. | | Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |
From: phil-news-nospam on 5 May 2008 14:55 In alt.tv.tech.hdtv bud-- <remove.budnews(a)isp.com> wrote: | Previously you said Martzloff "flubbed the experiment". I remember that. You were telling me about some information he had obtained from some experiment. | Now you agree with Martzloff that branch circuit must be 200m for | transmission line behavior with 1.2 microsecond rise time. That's not a result of an experiment. I'm not so sure the exact distance is 200m for that exact rise time. But that is a subjective thing. We are likely not that far apart. It is a matter of degree to how different the calculations come out when figuring them with transmission line issues and ignoring those issues. | You say that doesn't apply because surges are faster. Martzloff uses 1.2 | us because that is a standard rise time for surges produced by lightning | as defined in IEEE standards. Martzloff did not say that was a defined standard in the statement you quoted. He just used it as an example to come up with the 200m figure. Do you have some other statement from Martzloff or someone else about the 1.2 microsecond rise time? | w_' professional engineer source says 8 micoseconds with most of the | spectrum under 100kHz. Even with 1 nanosecond rise time, most of the energy will be present in the spectrum below 100 kHz. That means nothing when the surge is strong enough to have energy above some frequency that is relevant to the whole system involved that can do damage. That frequency might be 100 Mhz for some thing, and 1 GHz for other things. Some surges, mostly from very close direct strikes, can have damaging energy well above 1 GHz. It will depend on how much inductance you have between the surge and the equipment that needs to be protected. That's why I suggest that a good protection scheme will include added inductance on the wiring at a level compatible with the normal use (more can be added to power than to cable TV). | You still have *no sources that support your belief* that risetimes are | far faster. I have experience and observation for that. I need no more. | Again you did not read what I wrote (what a surprise): | "I intended 'induced' meaning produced by including the most damaging - | strikes to utility lines." You are saying the most damaging strikes are induced? Or are you merely adding the most damaging direct strikes in with the induced surges as a set of surge classes that you want to consider together? Your wording is so bad in that one sentence that I cannot tell what you mean. It is vague and could satisfy more than one meaning. -- |WARNING: Due to extreme spam, I no longer see any articles originating from | | Google Groups. If you want your postings to be seen by more readers | | you will need to find a different place to post on Usenet. | | Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |
From: bud-- on 5 May 2008 15:08
Mike Tomlinson wrote: > In article <481f4eb2$0$31762$4c368faf(a)roadrunner.com>, Timothy Daniels > <SpamBucket(a)NoSpamPlease.biz> writes > >> Does that mean a combination of w_tom's "whole house protection" >> and individual "surge protectors" at those "critical devices"? That's >> what I've always felt would be prudent - not a single method of >> protection, but a combination. > > Yes, but the environment in which the protected dwelling is situated > should also be taken into account. For example, a house in Florida, > with its overhead power lines and frequent thunderstorms, would be a > more likely candidate for a combined approach to surge protection. > > On the other hand, installing Florida-levels of protection in a house in > the UK with its infrequent storms, reliable underground power supply and > a decent electrical system with properly earthed sockets, would be a > waste of money. > Nice description. What you use depends on risk, and value of what you are protecting. The IEEE guide has, for max protection (not including lightning rods) - adequate earthing - short 'ground' wires from cable and phone entry protectors to the 'ground' at the power service (to limit the voltage between power and signal wires) - power service suppressor - plug-in suppressor for high value "sensitive" electronics - especially equipment with both power and signal connections (all wires to protected equipment needs to go through the suppressor) -- bud-- |