surge suppression

I need to build a surge suppressor to go on the input of an alarm circuit. The circuit operates at 24.0 VDC. This is a two wire input
with an end of line resistor. I pulled an AC line toroid off an old RCA TV and plan to connect it in series with my alarm circuit. Across the other side of the toroid I plan to connect two 33.0 V MOV's in series, with the center of the two connected to chassis, (building) ground. This combination on the other side of the toroid will then be connected to the alarm input. Additionally across the alarm input will also be connected a 1.0 uf capacitor. My theory is: a transient first sees the inductor which by nature resists a change in voltage. Next come the series MOV's which should direct everything above 24.0 V between each side of the line and ground, to ground. And finally will be the cap which will hopefully take care of whatever is left. I know that there are commercially available filters on the market but I would really appreciate any thoughts on my idea. Thanks, Lenny
----uuuuuu----,________________ | l M l Line |,,,,, __l__ To alarm input in | | ____ M GND l | l -----uuuuuu----'_________l,______
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snipped-for-privacy@yahoo.com wrote:

It really does depend on so many factors. Such as what the bandwidth of the information content on your data input is. You don't want to filter out "transients" that are actually valid data. The nature of the "surges" that you want to protect against is also vital - not much point in putting in protection against 100J transient energy pulses, if they contain 1kJ..
However, one technique that may be worth considering is to insert an opto-isolator in the control signal link. That can protect the alarm input from a very wide range of input signal anomalies - worst case being that the opto isolator goes to that great chipshop in the sky..
-- Sue
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The input is aimply a DC voltage of about 15 volts. This is a 24 volt power limited circuit which has a supervision resistor at the end of the line. If the line opens the voltage will approach 24 volts and the system will see a fault but not an alarm. If the line is shorted or brought very close to zero volts the system will indicate an alarm. A fuse would seem to make sense but it is not permitted. It sounds crazy but there must be repeatability so circuit integrity cannot be compromised by an open fuse. By the same token on opto isolator cannot be used either because it circumvents the direct connection between the alarm initiating devices and the input to the panel. It makes for a frustrating endeavor trying to deal with the realities of the situation while staying within the guidelines of the original design. Lenny.
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snipped-for-privacy@yahoo.com wrote:

. Still not stated, where does the surge come from? Surge strength? At what level does damage occur? A fuse will not likely protect from a "surge", which is a very short duration event.
Your idea sounds reasonable. The capacitor could mask real short opens (not likely). Is one of the alarm lines grounded? Not obvious why both would float. I am reading that the MOVs will connect to panel ground (which is connected to building ground).
A diode from the alarm line toward the positive rail, and diode from ground toward the alarm line might work (line voltage can only go about 0.6V beyond rails). A resistor between the alarm line and diodes will reduce the surge current. But if too large it would affect alarming and trouble response.
I would be real careful modifying an alarm circuit because of liability issues. It would be a good idea to ask the alarm panel manufacturer for recommendations.
--
bud--



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First, thanks Danny for setting me straight on my theory. I remembered from my school days, (back in the Stone age) that inductors resist a change. Yes it is a current change, but can I get partial credit for that one ?
This is a five zone panel. As I said both terminals of the zone input are isolated from ground. In fact if an input should ground, either directly or by high resistance due to a moisture problem for instance on an initiating device somewhere within the zone, the system will detect a "ground fault" situation and go into trouble. Naturally this would have to be repaired, however in this condition the alarm system is still capable of detecting a short acrosss the input and such a condition will still initiate an alarm.
The nature of the surge is lightning. The site elevation is very high and we have a lot of ledge in the ground here in New Hampshire. My theory was that the transient always seems to come in on zone one for some reason. This was my theory because after each event its always zone one, as well as the microprocessor which shows to be in trouble.
The diode idea sounds interesting Bud. I can envision a diode reverse biased from each side of the input to ground, but why would I install diodes as you mentioned: ("A diode from the alarm line toward the positive rail"), Wouldn't that run the risk of directing the transient right into the positive rail?
The last panel board I repaced actually showed evidence of a flash mark betwee zone one negative side and ground. I'm not sure if this is a clue but the board common ground terminal just happens to be right next to the zone one negative terminal. So at the risk of sounding like an idiot I have to ask: does it seem possible that my theory of origin is backwards? Is there any way possible for my transient to enter the panel FROM ground, jump to the zone one negative terminal since its right next to the ground terminal, do its dirty work and then the rest is just a memory?
Also this is not the only alarm panel that gets destroyed in this immediate area of town. There are at least five other buildings situated within an intersection which regularly get hit as well. The town electrician has had engineers look at the problem over the years and he has never really gotten any answers, except something to the effect of "this is New Hampshire and we have alot of granite in the ground so lightning damage is inevitable". I have to wonder how does the antenna and transmitting equipment in the Empire State Building survive Summer, and for over 60 years?
Last year I brought the electric utility company into this as well. We checked for ground loop. We monitored neutral with respect to ground for over a month. We had a recording line monitor installed but as luck would have it the panel survived and there were no significant events to be recorded during that period.
I should also mention that there is a transient suppressor in the electrical panel. The electrical panel is grounded using # 4 wire with three ground rods spaced over a two foot area. We installed a three stage power conditioner ahead of the alarm panel. It consists of RLC filters including MOV s. And on the primary side of the alarm power transformer I connected two 130V MOV's across neutral and hot with the center, (as drawn in my diagram above) connected to ground. Thanks again for everyones ongoing input. Lenny
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snipped-for-privacy@yahoo.com wrote:

There are a couple of excellent sources of information on surges and surge protection. One is from the IEEE: <http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf
The other is from the NIST and is aimed at the unwashed masses: http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf
Unfortunately, they may help with general principles but may not give a lot of useful help for your problem.

. If you want to see if it is zone 1, you could swap zone 1 with another one. This might be useful information. If it is zone 1, you could look for a cause along the circuit.
I assume from the description, the microprocessor program "crashes" and the microprocessor is reset. That sounds like a glitch getting into the logic. Could be coupled from the power line or alarm loop. .

. Yup. Depends on the strength of the surge and what energy the rail can absorb. I suggested possibility of a series resistor to limit the current (but that could impair trouble/alarm response).
If you are replacing boards already, the diodes are more useful than if you are just getting false alarms.
Your idea sounds practical. Not sure how much useful inductance you will get from a toroid. .

. If a surge comes in on power wires and produces 1000A to earth through a very good 10 ohm impedance to earth, the 'ground' at the service panel rises 10,000V above 'absolute' ground potential. With higher resistance to earth, as you have, a much smaller current to earth will elevate the power 'ground'.
If the only earthing electrode is a single ground rod, as a rule of thumb 70% of the voltage drop is in the first 3 feet from the rod. If you have 10,000V to 'absolute' ground, there will be 7,000V from the power 'ground' to earth 3 feet from the rod.
A 'near' lightning strike to earth produces earth currents that can put a high voltage between different earth contacts, like the power system 'ground' and a pad mounted compressor/condenser.
Path from zone 1 wires to another earth path? Capacitive coupling?
The IEEE guide has some information on ground potential rise starting pdf page 39.
Poor earthing conditions could give problems with 'ground' potential differences.
------------------------- Near lightning strikes can directly induce voltages with wires acting as "long wire" or "loop" antennas. A loop could be alarm wires and power wires, with a capacitive connection where an alarm wire goes past a 'ground' and the loop closing at the alarm panel. Voltage depends on the area of the loop.
The NIST guide says (guide page 14): "Intruder alarm systems using wires between sensors and their central control unit can be disturbed - and damaged in severe cases - by lightning striking close to the house. The wires necessary for this type of installation extend to all points of the house and act as an antenna system that collects energy from the field generated by the lightning strike, and protection should be included in the design of the system, rather than added later by the owner."
As I wrote "it would be a good idea to ask the alarm panel manufacturer for recommendations."
High elevation could produce high lightning activity and give problems with direct pickup. .

. Anything can be protected. Some protection can be expensive. Any nearby engineering schools for advice? .

. It is in a big metal box (actually just a frame). You can limit the voltage from the antenna, power, phone,... to the box. Even though the voltages may be thousands of volts above 'absolute' ground, the difference between wires is safe. .

. Neutral and ground should be bonded at the service panel. Measured at the alarm panel? Would seem like someone at the utility would have some ideas. .

. You generally want rods 6 ft apart. When you have a lot of rock there arent great answers.
With a poor connection to earth, much of the protection is to have all the wiring (and as much other as practical) float up together on a strong surge. .

. At the alarm panel, if there is current through the MOVs to power ground, the 'ground' potential at the alarm panel can shift relative to the service 'ground'. When using a plug-in suppressor, the protection is all wires float up together. But that could produce a ground potential rise problem with alarm wires. With a service panel suppressor there shouldn't be much action at the alarm panel.
--
bud--


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On Jul 12, 3:33 pm, snipped-for-privacy@yahoo.com wrote:

That means a surge was seeking earth ground. A diode or protector between two wires would do nothing, may see no surge voltage, or may even distribute that surge to all other wires. A surge on all other wires has more destructive paths to earth. Surge is still seeking earth ground which means a protector between two wires may even make an alarm panel is one best and destructive paths to earth.
Appreciate that Bud is a sales promoter - not technically trained. His sales must avoid discussion of surges that typically cause damage. Destructive surges must be diverted where that surge energy get dissipated harmlessly. Plug-in protectors claim to absorb what three miles of sky could not stop. Any such protection is easily
The trivial surge that typically cause no damage is made less by an inductor and irrelevant by a diode (or transzorb) between incoming alarm wires. But the surge that causes damage enters on any or all wires seeking earth ground. Voltage of this surge will increase as necessary to connect that current to earth - overwhelm any protection inside an alarm circuit - which explains why an inductor alone does not provide protection.
The protectors promoted by Bud will either provide a surge more paths destructively through the alarm panel OR not even see that surge voltage while the surge continues past doing damage. Effective protection makes a trivial surge irrelevant AND diverts the serious (typically destructive) surge where it can be harmlessly dissipated AND does not pass through alarm circuits. Best protection diverts typically destructive surges into earth (all wires including AC electric) and is best when separated from the alarm panel. That separation also increases protection.
Post your questions in alt.security.alarms .
What will an inductor do? Do you remember a current source? Voltage will increase as necessary to blow through that inductor. Nothing stops or absorbs typically destructive surges. To avert damage from a current source, you must give that current source what it wants - a connection to earth. That is what effective protectors do.
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w_tom wrote:

. Appreciate that w_ is an internut nut that uses google-groups to search for "surge" so he can share his 'wisdom'.
Lacking valid technical arguments for some of his arguments, w_ tries to discredit those who expose his drivel. My only association with the surge protection industry is I have some surge protectors.
And I am an electrical engineer. .

. The discussion was minimally about plug-in suppressors, but they are w_'s main fetish.
w_ has a religious belief (immune from challenge) that surge protection must use earthing. Thus in his view plug-in suppressors (which are not well earthed) can not possibly work. The IEEE guide explains plug-in suppressors work by CLAMPING the voltage on all wires (signal and power) to the common ground at the suppressor. Plug-in suppressors do not work primarily by earthing (or stopping or absorbing). The guide explains earthing occurs elsewhere. (Read the guide starting pdf page 40).
Some of what w_ says is quite good. Some of it is absolute nonsense. Lots of luck figuring out which is which. .

. It is likely from the OPs description that the surge is relatively low energy arriving on the alarm wires. Low energy means the surge could, for example, be absorbed by a MOV. A major issue is maintaining the alarm loop integrity. .

. Airplanes must drag an earthing chain.
--
bud--


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bud-- wrote:

Watch it! Tom thinks that means you are nothing more than a Tsnobbish V repairman.

The _Wacko_ Troll doesn't understand that the surge wants to complete the circuit which may, or may not be 'ground'. If it is an induced current, the entire circuit can be isolated from ground, and his concept will do absolutely nothing to help. If it is a spike that comes through the utility company's transformer, it doesn't need to go to ground, even though the center tap may be grounded. It has to be shunted back to the transformer, not to ground.

The first CMOS based alarm panels I saw in the early '70s had a horrible failure rate. A friend owned an alarm business and asked for help. After talking with the manufacturer, they modified the circuit board to include a low value inductors on every input & output. They were nothing more than an inch of copper trace that was a square wave of about seven cycles. That took car of 99% of his problems. Some intermittent problems were traced to passive IR sensors, and air leaks in the building. ON cold, wind nights, they would set off the alarm. Other intermittent problems were caused by people moving furniture and displays that redirected the heating & air conditioning airflow.
In some cases, a shielded, twisted pair of cable to the sensors stopped the problems.

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wrote:

If Michael had sufficient electrical knowledge and underlying experience, then a surge made irrelevant by an inductor should never damage anything. A surge that trivial was irrelevant according to 1970 standards for electronics. Michael's inductor solution was not even sufficient to meet those 1970s standards.
Surges that overwhelm properly installed internal protection are not the tens of volts solved by inductors. Effective protection means surges, capable of creating tens of thousands of volts, are made irrelevant. Such surges would blow through inductors as if inductors did not exist.
All electronic appliances must withstand hundreds of volts without damage. Surges that don't seek earth ground are so trivial as to be made irrelevant by the appliance design. Surges that seek earth ground can create tens of thousands of volts. Three miles of sky could not stop that surge. Will tiny inductors stop what three miles of sky could not? No wonder Michael posts disparaging remarks to prove his knowledge. Indictors were even insufficient to meet pre-1970 standards. How does an inductor stop or absorb surges capable of creating tens of thousands of volts? It doesn't.
Michael made a mistake. Michael routinely lets his emotions and hate decide how to attack this poster. Michael never bothers to post a technical rely for fear of again being exposed as a technical lightweight. Michael now tells us a silly little inductor will stop or absorb what even three miles of sky could not stop. Of course not. Those trivial surges that don't seek ground can be made irrelevant by transzorbs and other well proven solutions. But the typically destructive surge requires solutions provided previously by this author.
Surges that typically cause damage must be earthed before getting into an alarm panel. Any alarm panel must be designed to make irrelevant any surge that does not seek earth. More often used on signaling wires are avalanche diodes - not MOVs. What is required to protect alarm from typically destructive surges? Protection routinely integrated with earth ground, as alarm installers in alt.security.alarms have understood long ago. Unlike Michael Terrell, their posts are backed by experience and knowledge. No inductor will stop or absorb typically destructive surges. That solution, justified by insults, was insufficient even for pre-1970 standards.
An alarm panel must be designed and installed so that direct lightning strikes to AC electric - the most common source of destructive surges - does not create damage.
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w_tom wrote:

Tom, once again you are proving that you are an idiot. That PCB trace inductor and the capacitance of the trace to the ground plane formed a simple low pass filter. Of course, I don't expect you to understand this, or anything else about electronics. That low pas filter slowed down any induced spike, which reduced the peak voltage, which prevented damage to the CMOS IC input.

Keep blathering, and prove your ignorance, yet again.

Sure about that? Show some valid links, and people who agree with your screwed up thinking.

Just admit that you don't know what the hell you are talking about, everyone else has already figured that out for themselves.

Reduced to posting more lies, Tommy? Every time I post a link you ignore it. Like proof that computer power supplies are not required to work at 90 VAC. I posted a long list of specifications off approved ATX power supplies, and not one was rated for 90 VAC. then you started whining about an old, abandoned standard for business machines and minicomputers.

Bullshit. A lot of older alarm panels were battery powered, and were not connected to any ground, anywhere in the system. They would run a month or more on a couple large 1.5 VDC telephone cells. It was when they went to solid state and MPU controlled panels that they went to rechargeable gel cells. I was there,, teaching the proper way to install the hardware for a new alarm company, as well as building their central monitoring station.

The only diodes I saw on the alarm PCBs were 1N4001.

Get real! Some of those guys are idiots.

Ge Tommy, have you ever worked on an old fire alarm with the wind up code wheel? They have been around for about 100 years. Been there, done that. They used a loop that could run miles, with buildings connected in series. The code wheel sent a unique code for each alarm system, and they were monitored at the fire house, or other location. A fixed current was fed through the loop and monitored for faults.

of course not, but it will slow the rise time enough to prevent damage. You would understand this if you understood basic electronics.

What is your hang-up with per 1970? Show me any alarm panel build with CMOS ICs that was made before 1970. As far as insults, you get back insults, because you try to insult everyone who tries to show you why you are wrong. You must live a really sad and empty life. I really feel sorry for you, but I will not let you spread lies and myths to people who don't know any better than to listen to your childish rants and lies. Have you ever had a girlfriend? In your case yo might have to pay for it, because you would be telling her lies as she tried to put up with you.

Yawn. A direct strike will damage an alarm system, as well as the building, the phone lines, the electrical service, cable TV drops, and even destroy battery powered electronics with EMP induced current. I have lost battery powered thermometers and VGA monitors that were not connected to the AC line, or a computer when lightning struck 15 feet from the building. Once again, your arrogance is only exceeded by your ignorance.
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wrote:

Which is why the telephone system is every town is turned off during thunderstorms. Professional papers report a telephone CO will suffer about 100 surges during every thunderstorm. Since direct lightning strikes to their overhead wires all over town causes so much damage. And since EMP is so destructive, then telcos shut down during thunderstorms.
Since that EMP is so destructive, then radios are routinely destroyed by such fields.
Oh? Your car radio works fine even when lightning strikes the adjacent street sign? Oh. Telcos never shut down during thunderstorms? Their $multi-million computer never damaged causing five days of no service? How can this be when Michael Terrell is so knowledgeable?
It is routine to suffer direct lightning strike even to household appliances. A direct strike to AC electric wires on utility poles is a direct strike to all household appliances. So you routinely replace these appliances? Oh. Some facts to actually help the OP - and posted without insults.
First, any protection that would work adjacent to electronics is installed inside electronics. Electronics (ie CMOS) must withstand hundreds of volts without damage. Newer CMOS interface IC are required (by industry standards) to withstand 2000 or 15,000 volts without damage. Internal protection that even makes trivial EMP surges irrelevant. EMP transients being some of the easiest to make irrelevant.
Transient that are typically destructive (that can overwhelm internal protection) must be earthed before entering a facility. Properly earthed protection so that surge energy gets dissipated harmlessly in earth AND so that protection inside all electronics (including alarm panels) is not overwhelmed.
Michael is only a technician which is why he hypes fear of EMP. He would not even know about interface ICs that must withstand 2Kv and 15Kv without damage. That protection is implemented at the design level - often overlooked and unknown to technicians.
A greatest threat to alarm panels are direct lightning strikes to incoming wires such as AC electric and telephone. These are direct lightning strikes to the panel if the transient is not properlly earthed before entering a building. These direct strikes can overwhelm protection that is standard in all alarm panels.
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Wacko wrote:

YAwn. Wacko continues to parade his ignorance for everyone to see.
Telephone systems are low impedance, and the remaining copper is protected by a multitude of arrestors and protectors. Gas discharge and MOV devices have replaced the hundred year old devices. More an more is fiber optic, and in parts of the US it is fiber into the customer's home.

How many radios are within a few feet of a lightning strike? How many radios are built with a high impedance untuned front end? How many are built with no shielding? Have you ever seen the inside of a radio?

More of Wacko's cut & paste ignorance.

Really? What about the power transformer between the utility and the house?

Only if they are damaged. I have never had anything damaged that was plugged into a surge protector, while things that weren't protected were damaged. I had a direct strike to my TV antenna. The mast was a few inches from the AC where it entered the building. It destroyed the underground telephone, TV antenna and power lines. It destroyed the phone line to the street, the line card, and the copper pair to the Central Office. It didn't touch the TV, Microwave, refrigerator, or anything else that used plug in protection. It tripped the main breaker where the whole house protector was located, but a stereo and several other items that weren't used with surge protection.

Bullshit. Electronics are built to a price point, and it is listed in the warranties that lightning damage isn't covered. Once again, you are parading your ignorance.

Not always possible, Wacko. Sometimes the lightning hits the facility before entering it's power system. You would know this, if you knew anything about the subject.

harmlessly? You've never seen the steam and flying dirt as that energy is conducted to ground?

More of Wacko's lies. I used the Maxim protected RS232 ICs not long after they were developed. Their policy of free samples was handy wen designing new products.

According to your lies in other messages you've posted, that can never happen.

A direct strike can burn the building down. It happens quite often in Florida. Even buildings with lightning rods have been hit and damaged. I have seen chunks of concrete blow out off buildings and 11 GHz microwave CARS equipment destroyed, with it mounted to the side of the tower, and enclosed in a NEMA box that should have been a Faraday shield. All the inputs were protected to current industry standards, yet it did over $6,000 damage and took six months to have the factory refurbish.
Once again, Wacko is pulling his 'facts' out of his fat ass.
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wrote:

So a low pass filter will stop what three miles of sky could not. That is what Michael Terrell is claiming. His proof? He posts insults.
Any surge that causes ground to explode means earthing was probably installed by a Michael Terrell. Even code requirement for human safety make all earthing sufficient to earth the largest surge without 'exploding'. Meanwhile, those who want effective surge protection simply read numeric specifications posted by Michael. Oh. Michael could not find a single plug-in protector that claims protection from earth type of surge. Why then does Michael recommend plug-in protector and say 'whole house' protectors cannot provide protection?
Every responsible source says what the effective protector does - directly contradicts your diatribe.

So where does that plug-in protector dissipate surge energy harmlessly in earth? It does not. Instead it does like your magic low pass filter? It stops and absorbs what even three miles of sky could not stop? No effective protector does that. So Michael Terrell posts no manufacturer specs. No plug-in protector even claims to protect from the typically destructive surge. However because it can protect from surges that typically cause no damage, Michael Terrell recommends it.
Low pass filter is one example of internal protection found routinely in all electronics designs. Other solutions are also designed in as provided in my previous posts. Internal protection that makes a plug-in protector useless. Internal protection also requires destructive transients be earthed distant from electronics. The direct lightning strike to an alarm panel is a direct strike to utility wires out on the street. CMOS circuits even in the 1970s would meet those 1970s standards for surges with no damage. Today, CMOS circuits must be even more robust. An lone inductor cannot provide what is required.
Michael - why do you so hate as to post a long diatribe irrelevant to the OP's questions? Why do you waste everyones time with insults AND few (if any) technical facts. Your inductor on an input line or a low pass filter does not provide the protection that CMOS circuits needed even in the 1970s. If you had design experience, then you would have known that.
CMOS circuits must not have protection only for trivial tens of volts. That CMOS must be so robust in the 1970s as to withstand hundreds of volts - without damage. Today, we design CMOS circuits to withstand thousands and tens of thousands of volts - without damage. Michael's inductor on an input line will not accomplish what is required and what the OP is requesting.
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w_tom wrote:

. Another of w_'s hallucinations. Michael wasn't talking about a direct strike. .

. If not hindered by religious blinders w_ could read the answer in the IEEE guide (starting pdf page 40). The IEEE guide explains plug-in suppressors work by CLAMPING the voltage on all wires (signal and power) to the common ground at the suppressor. Plug-in suppressors do not work primarily by earthing (or stopping or absorbing). The guide explains earthing occurs elsewhere. .

. Humor for the day.
For real science read the IEEE and NIST guides. Both say plug-in suppressors are effective.
There are 98,615,938 other web sites, including 13,843,032 by lunatics, and w_ can't find another lunatic that says plug-in suppressors are NOT effective. All you have is w_'s opinions based on his religious belief in earthing.
Never answered - embarrassing questions: - Why do the only 2 examples of protection in the IEEE guide use plug-in suppressors? - Why does the NIST guide says plug-in suppressors are "the easiest solution"? Why dont airplanes drag an earthing chain?
--
bud--

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| w_tom wrote:
|> wrote: |>> Tom, once again you are proving that you are an idiot. That PCB |>> trace inductor and the capacitance of the trace to the ground plane |>> formed a simple low pass filter. Of course, |> |> So a low pass filter will stop what three miles of sky could not. |> That is what Michael Terrell is claiming. | . | Another of w_'s hallucinations. Michael wasn't talking about a direct | strike. | . |> So where does that plug-in protector dissipate surge energy |> harmlessly in earth? It does not. | . | If not hindered by religious blinders w_ could read the answer in the | IEEE guide (starting pdf page 40). The IEEE guide explains plug-in | suppressors work by CLAMPING the voltage on all wires (signal and power) | to the common ground at the suppressor. Plug-in suppressors do not work | primarily by earthing (or stopping or absorbing). The guide explains | earthing occurs elsewhere.
Clamping does not make surge energy disappear. It is nothing more than a form of diversion. It creates a path, when the voltage difference is high enough, to an alternate wire, such as ground. Now the surge energy has 1 or 2 more paths to go, for a total of 2 or 3 (depending on whether the wire the voltage is clamped is and end point, or the middle of a run of wire). Just because the clamping has created the path does not mean all of the energy will go that way. The proportions depend on the characteristic impedance, as that is the only impedance that has an immediate effect with reflection time frame short enough to not need to be considered.
BTW, the reverse polarity will propogate back into the wire carrying the original surge. This has the effect of significantly reducing the voltage difference between the conductors. If this is done between all pairs of conductors (both current carrying conductors whether one of them is a grounded conductor or not, plus the ground itself) then it can reduce a large voltage difference between any two of the wires to hopefully a level that won't damage the appliance.
But even this clamping across conductors does not eliminate delta-time voltage exposure. If the voltage on these wires was 0 and X, then the clamped result will be close to X/2 and X/2. So while the difference is now insignificant, it has only reduced the leading edge to half. To the extent that the circuitry of the appliance changes the voltage over time differently in different places (e.g. a reactive circuit component), it can still end up with a voltage difference internally and damage something such as a sensitive semiconductor device like a CPU.
You can significantly reduce delta-time voltages by means of an inductor in series and/or a capacitor in parallel to the line leading to the appliance being protected.
A combination of protection mechanisms, as long as they are installed properly, can provide the best level of protection for appliances. Just how much protection to use is a balance among the cost of protection, the cost of loss, and the risk factors. There is no universal answer. The optimal choice is made by people that understand what all is going on, not by people that parrot documentation suited only for specific situations, or intended to describe specific protection devices.
|> No plug-in protector even claims to |> protect from the typically destructive surge. | . | Humor for the day. | | For real science read the IEEE and NIST guides. Both say plug-in | suppressors are effective.
... for certain kinds of surges. They are NOT universal protection for all kinds of surges.
The "destructive" surges he speaks of may be the ones that vaporize plug-in suppressors. A direct strike can do that.
| There are 98,615,938 other web sites, including 13,843,032 by lunatics, | and w_ can't find another lunatic that says plug-in suppressors are NOT | effective. All you have is w_'s opinions based on his religious belief | in earthing.
Why is it that you always seem to want a binary answer about whether a surge protection device is or is not effective? The true and correct answer will be "it depends".
| Never answered - embarrassing questions: | - Why do the only 2 examples of protection in the IEEE guide use plug-in | suppressors?
Because the IEEE guide you looked at is a guide about how to use plug-in suppressors to their greatest effectiveness.
| - Why does the NIST guide says plug-in suppressors are "the easiest | solution"?
Because the average person is not skilled to do the correct installation of other kinds of protection.
| ? Why don?t airplanes drag an earthing chain?
That would make it too easy for terrorists to grab hold of and yank the plane down.
Silly question, silly answer.
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snipped-for-privacy@ipal.net wrote:

. Clamping makes the voltage between wires going to the protected equipment safe for the protected equipment. .

. Repeating: "Plug-in suppressors do not work primarily by earthing."
And repeating: "The guide explains earthing occurs elsewhere."
Perhaps if you read and understood the example in the IEEE guide, starting pdf page 40.... .

. Francois Martzloff was the NIST guru on surges. He did research and has many published papers on surges and surge suppression. On transmission line behavior Martzloff writes: "From this first test, we can draw the conclusion (predictable, but too often not recognized in qualitative discussions of reflections in wiring systems) that it is not appropriate to apply classical transmission line concepts to wiring systems if the front of the wave is not shorter than the travel time of the impulse. 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."
I have posted this at least twice previously in response to your comments on transmission line behavior. Your response was that Martzloff "flubbed the experiment". You have never provided a supporting source for you belief.
Provide a source that agrees with you that transmission line effects have to be considered for surges in other than large buildings. .

. The IEEE guide "was written to make the information developed by the [IEEE Surge Protection Devices Committee] more accessible to electricians, architects, technicians, and electrical engineers who were not protection specialists." The guide includes for protection: 1 earthing of the systems 2 short connections between signal entry protectors and power system earthing 3 service panel suppressors 4 plug-in suppressors for 'sensitive' electronics, particularly with both signal and power connection
The guide is for general surge protection using the most common techniques. It is not aimed at "specific situations". You show little indication you have read or understood the guide. I realize you didnt write it, so it probably isn't worth reading.
My comments in response to w_ are disproportionately about plug-in suppressors because of the nonsense w_ posts about them. .

. If by direct strike you mean a direct lightning strike to a building, protection requires lightning rods. There is no point in talking about protection without rods.
For surges coming in on utility wires, the impedance of the branch circuit greatly limits the current, and thus energy, that can reach a plug-in suppressor. Investigations by Martzloff with surges up to 10,000A at a power service (the maximum reasonable surge) and branch circuits 30 ft and longer with a MOV at the end, showed surprisingly small energy absorption at the MOV. The maximum energy dissipated in the MOV was 35 Joules. In 13 of 15 cases it was 1 Joule or less. One reason is the branch circuit impedance. The other is that at about 6,000V (US) there is arcover from service panel busbars to enclosure/ground/neutral/earth. After the arc is established the arc voltage is hundreds of volts. That dumps most of the surge energy to earth. Receptacles (US) will also arc-over at about 6,000V.
Neither service panel or plug-in suppressors protect by absorbing energy. The absorb energy in the process of protecting. .

. w_ says never. What I have read from many Martzloff papers and other sources is that plug-in suppressors with high ratings connected properly are very unlikely to fail. That is why some plug-in suppressors can have connected equipment warrantees. .

. Your comment is beyond stupid. Perhaps if you read the guide.... .

. The NIST guide covers the same basic protection as the IEEE guide. It also has a "contractor" section with more technical information. Perhaps if you read the guide.... .

. It is a serious question. w_ says you cant protect without the protector directly earthing the surge. Then it is not possible to protect airplanes.
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| snipped-for-privacy@ipal.net wrote:
|> | w_tom wrote: |> |> So where does that plug-in protector dissipate surge energy |> |> harmlessly in earth? It does not. |> | . |> | If not hindered by religious blinders w_ could read the answer in the |> | IEEE guide (starting pdf page 40). The IEEE guide explains plug-in |> | suppressors work by CLAMPING the voltage on all wires (signal and power) |> | to the common ground at the suppressor. Plug-in suppressors do not work |> | primarily by earthing (or stopping or absorbing). The guide explains |> | earthing occurs elsewhere. |> |> Clamping does not make surge energy disappear. | . | Clamping makes the voltage between wires going to the protected | equipment safe for the protected equipment.
See what I said later in that post you are replying to. Sure, it does equalize the difference for the most part. Other aspects of the surge are not affected, or are affected in only minimal ways. For example the surge front waveform is reduced because some of the energy can go across the clamp and take another path away from the appliance. But this is only reducing the energy to some fraction that can still be enough to cause damage.
|> It is nothing more than a |> form of diversion. It creates a path, when the voltage difference is high |> enough, to an alternate wire, such as ground. Now the surge energy has |> 1 or 2 more paths to go, for a total of 2 or 3 (depending on whether the |> wire the voltage is clamped is and end point, or the middle of a run of |> wire). Just because the clamping has created the path does not mean all |> of the energy will go that way. | . | Repeating: | "Plug-in suppressors do not work primarily by earthing."
You have sounded like a broken record for a long time. And why do you even need to say this?
| And repeating: | "The guide explains earthing occurs elsewhere."
You still sound like a broken record.
| Perhaps if you read and understood the example in the IEEE guide, | starting pdf page 40....
Maybe you can just point at a statement I have made that contradicts it.
Your _big_ problem is your failure to be able to discuss these points you keep referring to. That suggests to me you don't really understand what IEEE says enough to be able to defend it on your own. All you do is point at it ... even in cases where it is irrelevant (e.g. cases where someone did NOT contradict it, or was discussing something unrelated).
Hint: pointing does not make other people wrong
What I suggest you do is read what you want to base your arguments on very thoroughly and build your own knowledge base so you can defend it completely independently. Then you need to actually focus on something someone says that you think is wrong, and explain (not point to some document) why you believe it is wrong, and provide the correct statement you think is right (and do this without pointing away at some document).
|> The proportions depend on the characteristic |> impedance, as that is the only impedance that has an immediate effect with |> reflection time frame short enough to not need to be considered. | . | Francois Martzloff was the NIST guru on surges. He did research and has | many published papers on surges and surge suppression. | On transmission line behavior Martzloff writes: | "From this first test, we can draw the conclusion (predictable, but too | often not recognized in qualitative discussions of reflections in wiring | systems) that it is not appropriate to apply classical transmission line | concepts to wiring systems if the front of the wave is not shorter than | the travel time of the impulse. 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."
You've quoted this before. In all cases I can remember, you quoted it inapplicably. The evidence of your error exists right there in the words you quoted. The part that says "if ..." is a conditional. It means that the statement being made only applies under certain circumstances. Yet you (who don't seem to understand this) quote this even where it does not apply (e.g. in cases where the if-clause is not met).
| I have posted this at least twice previously in response to your | comments on transmission line behavior. Your response was that Martzloff | "flubbed the experiment". You have never provided a supporting source | for you belief.
The "supporting source" is the very statement you quote. Again, it is a conditional statement that depends on a specific kind of impulse/waverform timing.
His "flubbed" experiment was not one to characterize all surges. I say it was "flubbed" because it did not meet the needs YOU are trying to apply it to (which seems to be the assumption that all surges are alike).
| Provide a source that agrees with you that transmission line effects | have to be considered for surges in other than large buildings.
I don't intend to do that. I don't need to. It is not my objective or obligation to make you believe something. It should be up to you to find out the truth, and figure out and understand the circumstances where your statements apply and do not apply.
|> A combination of protection mechanisms, as long as they are installed |> properly, can provide the best level of protection for appliances. Just |> how much protection to use is a balance among the cost of protection, |> the cost of loss, and the risk factors. There is no universal answer. |> The optimal choice is made by people that understand what all is going |> on, not by people that parrot documentation suited only for specific |> situations, or intended to describe specific protection devices. | . | The IEEE guide "was written to make the information developed by the | [IEEE Surge Protection Devices Committee] more accessible to | electricians, architects, technicians, and electrical engineers who were | not protection specialists." | The guide includes for protection: | 1 earthing of the systems | 2 short connections between signal entry protectors and power system | earthing | 3 service panel suppressors | 4 plug-in suppressors for 'sensitive' electronics, particularly with | both signal and power connection | | The guide is for general surge protection using the most common | techniques. It is not aimed at "specific situations". You show little | indication you have read or understood the guide. I realize you didn?t | write it, so it probably isn't worth reading.
This is a guide for people who are only going to be doing minimal levels of protection. A minimal level happens to be adequate for most people. This guide does not cover the extensive protection needed that balances between special requirements and the rare and very destructive extreme surges.
| My comments in response to w_ are disproportionately about plug-in | suppressors because of the nonsense w_ posts about them.
Maybe you should just disregard him entirely.
|> |> No plug-in protector even claims to |> |> protect from the typically destructive surge. |> | . |> | Humor for the day. |> | |> | For real science read the IEEE and NIST guides. Both say plug-in |> | suppressors are effective. |> |> ... for certain kinds of surges. They are NOT universal protection for all |> kinds of surges. |> |> The "destructive" surges he speaks of may be the ones that vaporize plug-in |> suppressors. A direct strike can do that. | . | If by direct strike you mean a direct lightning strike to a building, | protection requires lightning rods. There is no point in talking about | protection without rods.
Amazing. You managed to make a statement of some significant "fact" without pointing to some document that may not be applicable.
| For surges coming in on utility wires, the impedance of the branch | circuit greatly limits the current, and thus energy, that can reach a | plug-in suppressor. Investigations by Martzloff with surges up to | 10,000A at a power service (the maximum reasonable surge) and branch | circuits 30 ft and longer with a MOV at the end, showed surprisingly | small energy absorption at the MOV. The maximum energy dissipated in the | MOV was 35 Joules. In 13 of 15 cases it was 1 Joule or less. One reason | is the branch circuit impedance. The other is that at about 6,000V (US) | there is arc?over from service panel busbars to | enclosure/ground/neutral/earth. After the arc is established the arc | voltage is hundreds of volts. That dumps most of the surge energy to | earth. Receptacles (US) will also arc-over at about 6,000V.
First of all, an MOV is not going to absorb much energy. It is a device that creates a low impedance path between two conductors. The energy it absorbs is the current, times the voltage DROP, integrated over time.
What is of more concern is where the rest of the energy went. It goes out in all directions in response to impedance characteristics.
| Neither service panel or plug-in suppressors protect by absorbing | energy. The absorb energy in the process of protecting.
Maybe you can explain what your statement means. Or maybe you can't.
|> | There are 98,615,938 other web sites, including 13,843,032 by lunatics, |> | and w_ can't find another lunatic that says plug-in suppressors are NOT |> | effective. All you have is w_'s opinions based on his religious belief |> | in earthing. |> |> Why is it that you always seem to want a binary answer about whether a |> surge protection device is or is not effective? The true and correct |> answer will be "it depends". | . | w_ says never. What I have read from many Martzloff papers and other | sources is that plug-in suppressors with high ratings connected properly | are very unlikely to fail. That is why some plug-in suppressors can have | connected equipment warrantees.
The existance of a warrantee does not ensure protection. Surges do not give a damn about the warrantee. If they did, they'd probably make more of an effort to destroy everything just to spite the owner of the devices.
|> | Never answered - embarrassing questions: |> | - Why do the only 2 examples of protection in the IEEE guide use plug-in |> | suppressors? |> |> Because the IEEE guide you looked at is a guide about how to use plug-in |> suppressors to their greatest effectiveness. | . | Your comment is beyond stupid. Perhaps if you read the guide....
Perhaps if you applied the guide correctly.
I read it a long time ago. It didn't cover all aspects of protection. Since it was intended for specific readers, it doesn't even need to cover all aspects.
|> | - Why does the NIST guide says plug-in suppressors are "the easiest |> | solution"? |> |> Because the average person is not skilled to do the correct installation of |> other kinds of protection. | . | The NIST guide covers the same basic protection as the IEEE guide. It | also has a "contractor" section with more technical information. Perhaps | if you read the guide....
Read it, too, a long time ago. I have no reason to go back. You have not stated any such reason.
|> | ? Why don?t airplanes drag an earthing chain? |> |> That would make it too easy for terrorists to grab hold of and yank the plane |> down. |> |> Silly question, silly answer. | . | It is a serious question. w_ says you can?t protect without the | protector directly earthing the surge. Then it is not possible to | protect airplanes.
It seems you have a broad lack of understanding, despite reading all these various guides.
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snipped-for-privacy@ipal.net wrote:>

Airplanes also don't drag along an ac cord for power. They are closed systems surrounded by a conducting shell..
Surge protectors do a reasonable job as long as the protected equipment has no other connection referenced to ground other than the power cord.
Eric
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| snipped-for-privacy@ipal.net wrote:> |> |> |> | ? Why don?t airplanes drag an earthing chain? |> |> |> |> That would make it too easy for terrorists to grab hold of and yank the plane |> |> down. |> |> |> |> Silly question, silly answer. |> | . |> | It is a serious question. w_ says you can?t protect without the |> | protector directly earthing the surge. Then it is not possible to |> | protect airplanes. |> |> It seems you have a broad lack of understanding, despite reading all these |> various guides. |> | | Airplanes also don't drag along an ac cord for power. They are closed | systems surrounded by a conducting shell..
I was going to next try the argument "if the airplane drags along a ground wire, it might contact power distribution wires and short them out, creating legal liability for the airline". If he's going to insist on considering an absurd concept, then I'll give him logical, but equally absurd, answers.
Or I could just tell him he is being absurd.
| Surge protectors do a reasonable job as long as the protected equipment | has no other connection referenced to ground other than the power cord.
Right. And some emphasis is due on "reasonable". For most home use, this is just fine and the plug-in power strip type units I believe he refers to are adequate for the level of protection most people need.
Life gets more complicated when devices like radio transmitters need to have their own grounding. But this is outside the scope of the typical case where most people need protection. And the "resonable" protection isn't going to cover 100% of possible surges. But it might do well enough to reach 99%. Considering the infrequency of surges, and reduce that further by 1%, and reduce that even more by the number of people that never request fulfillment of a surge protection warranty, and considering the market avantage of having such a warranty listed on the product, I can see how this makes business sense.
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