Are surge protectors based on grounding or diode clipping?
- = - Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
snipped-for-privacy@at.BioStrategist.dot.dot.com wrote in news:htioft$8nr$ snipped-for-privacy@reader1.panix.com:
grounding. once the breakover voltage is reached,the surge is conducted to ground.
Otherwise,the surge would just find it's own way to ground,through your device,catastrophically. and you have to have a good ground,as grounds can float above true ground,particularly in poor soils,like Florida's sandy soil.
-- Jim Yanik jyanik at localnet dot com
Both. Most surge suppressors have a conducts-on-overvoltage element directly across the line, with a fuse or circuit breaker to keep the fire hazard low. Additional elements that connect to the protective ground pin are of secondary importance.
The conducts-on-overvoltage element is usually a metal oxide varistor, a kind of crude semiconductor breakover diode.
Thanks for both replies.
- = - Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
I would argue that. The differential surpressor is fine, but the common mode surge can do more harm and a lot of noise problems. Using an isolation transformer makes common mode problems impossible. Its a direct short to ground.
greg
snipped-for-privacy@zekfrivolous.com (GregS) wrote in news:htlreq$mlf$ snipped-for-privacy@usenet01.srv.cis.pitt.edu:
it's not a "diode",its just a sintered semi-metallic pellet that conducts once a certain voltage is reached. a "diode" is a P/N junction or a semiconductor/metal junction.
even the cheap suppressors I've bought had 3 MOVs,one for each leg to ground and from one leg to the other. I guess that's a "delta" config.
-- Jim Yanik jyanik at localnet dot com
cis.pitt.edu:
The metal oxide in a MOV is certainly a semiconductor. The breakover is due to avalanche multiplication rather than minority injection. The oldest ones were SiC (basically, just grinding wheels with electrodes bolted on). It has two leads, so it's a diode. It's made with a semiconductor, so it's a semiconductor diode. It isn't a rectifier diode, though. DIAC and current regulator two-terminal devices are also diodes, but aren't simple PN junction types (don't really rectify). Vacuum tubes are sometimes diodes, too (like my microwave oven's magnetron).
The protective ground connection is, in most situations, carrying no current. The MOVs that connect to that protective ground are not so much protecting the plugged-in device, as they are dumping transient energy in the building's wiring (protecting the building rather than the appliance). The internal suppressors on lots of consumer equipment only have one MOV, across the line, not the full trio that is common in third- party suppressor modules.
I thought there were NO supressors in most consumer equipment because its a liability.
Its the line to ground noise and surges that cause TTL computer type equipment to BOMB OUT. Ground has everything to do with functioning circuits, that use ground for reference. Of, course, its best not to use ground for reference.
greg
snipped-for-privacy@zekfrivolous.com (GregS) wrote in news:htmh5b$rcn$ snipped-for-privacy@usenet01.srv.cis.pitt.edu:
I never said otherwise. but it's NOT a "diode".
No,it's not.
from the Free Dictionary;
1.An electronic device that restricts current flow chiefly to one direction. 2. An electron tube having a cathode and an anode. ...Other Google examples for "diode definition" are essentially the same.
A thermistor is another semiconductor,with two leads,yet NOT a "diode",but a resistor.An MOV is closer to "resistor" than "diode". a Polyfuse is another semiconductor with two leads,yet not a "diode".
MOVs -shunt- surge energy to ground,through the wiring. sometimes,they cannot handle the energy,and blow apart.I've had to replace more than a few of them,living in the Lightning Capitol of the US,central Florida. Sometimes,the surge energy finds a better path through the protected device,with unfortunate results.
no,just an extra cost. plus,after they absorb a strike,they often need replacement,along with the blown fuse.
even with floating circuits,a lightning strike will find some path to ground. Probably one that is destructive.
-- Jim Yanik jyanik at localnet dot com
cis.pitt.edu:
How sad. Diode, meaning two electrodes... applies to a variety of semiconductor devices, and vacuum tubes. Not just rectifiers, but tunnel diodes and gunn diodes and those self-blinking LEDs (really oscillator integrated circuits with a lamp). The dictionary is wrong. MOVs are semiconductor devices equivalent to avalanche (Zener) diodes, but without any forward-bias conduction. They're semiconductor diodes in all senses of the words.
Well, here's is a disclosure of the biases which might be distorting my thinking: In February and August 2001 I lost two external modems to lightning (caused my line to be off-hook until disconnected modems) and someone on usenet told me to tie a ground to the modem. That particular computer (Ampro
2210 80186 hooked up to 1980 HP2621a terminal) with modems had previously survived 1988-1995 without problems (no phone surge supressor but one on power). In 2008 I lost two LCD monitors the same week during light rain. I am therefore excessively (and probably unreasonably) cautious of using computers during bad weather. Also in 1980 I took two semesters of EE for non-EEs (am a 1981 ChE).- = - Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
Do surge supressors exist for two-line phone connections?
WOuld it make sence to put a surge suppressor (what kind?) on my incoming phone line? Neighbors have complained of fried modems, but curiously I don't remember anyone ever telling mtheir computer got fried.
- = - Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
There should already be one inside the phone company's Network Interface.
-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
This applies to the US-
there are surge and lightning arrestors on phone lines where they enter a residence, and they're grounded to something good, like a water pipe for instance.
It works great.
Now if lightning surges hit your power then what happens?
a cheapo-garbage "surge protector" like a power strip or the like will use MOVs to short out line to neutral or even line to ground.
What happens if you throw a short across line to ground and can somehow clamp it to 600 volts or whatever? The numbers are made up, but concept is the same.
well, your ground ends up at 300 volts above actual earth ground where that device is located. This assumes your ground has the same impedance as the current carrying conductors.
So now your computer isn't really grounded, and floating at a potential way off what the phone like is at, which worst case is being protected to a really solid ground, and not hundreds of feet or wiring in your walls or whatever.
This is what blows up stuff like modems or devices that sit between your outlets and a phone line.
The best move is to install a service entrance surge supressor. They'll clamp surges at the best ground you've got, with the lowest possible impedance, and at your ground/nuetral bonding point not at your load where any attempts to do so are pretty useless across the extra fraction of an ohm.
You can easily test the resistance of your wiring at home too, and at the same time actually test if your ground is solid.
connect some large resistive loads like halogen lamps, hairdryer, toaster oven or whatever at and outlet. Measure the voltage drop when it's on. Break out the suicide cables and test that same device using line to ground.
Depending on how your place is wired, you may find that under an actual load, your ground is really awful. A volt meter won't pick crappy ground connections unless you are actually running real current through it, so just reading 120 across hot and ground and saying "looks good" really doesn't count.
Trying to suppress a surge with a $4 power strip connected though 5 junction boxes connected with BX cable can really just be a big joke.
residence, and they're
Some comments are somewhat specific to the US.
A couple of excellent sources of info on surge protection are:
from the IEEE, and a much simpler one from the US-NIST
With a strong surge current to the earthing electrode, the "ground" for the building can rise thousands of volts above "absolute" earth potential. You want power and phone (and cable) wires rise together. That requires a short ground wire from the telephone entrance protector to the earthing system at the power service.
MOVs to short out line
it to 600 volts or
device is located. This
off what the phone like
hundreds of feet or
outlets and a phone line.
If you RTFM, any competent plug-in suppressor manufacturer should tell you the phone wires have to go through the suppressor along with the power wires. The voltage on all wires is clamped to the ground at the suppressor. The voltage between the wires to the protected equipment is safe for the protected equipment. All interconnected equipment needs to be connected to the same suppressor, or external wires, like cable need to go through the suppressor. This is clearly explained in the IEEE guide starting pdf page 40, and shown in the examples at the end. Plug-in suppressors work primarily by clamping, not earthing.
surges at the best
ground/nuetral bonding point not
fraction of an ohm.
Service panel suppressors are a real good idea. I would particularly use one in high risk areas like Florida.
But from the NIST guide: "Q - Will a surge protector installed at the service entrance be sufficient for the whole house? A - There are two answers to than question: Yes for one-link appliances [electronic equipment], No for two-link appliances [equipment connected to power AND phone or cable or....]. Since most homes today have some kind of two-link appliances, the prudent answer to the question would be NO - but that does not mean that a surge protector installed at the service entrance is useless."
The NIST guide suggests most damage results from high voltage between power and phone/cable wires. A service entrance suppressor does not, by itself, limit that voltage.
time actually test
or whatever at and
and test that same
your ground is really
actually running real
"looks good" really
May well be worthwhile. But even with a good earth connection the building ground can rise thousands of volts.
boxes connected with
Neither the IEEE or NIST agree. Both guides say plug-in suppressors, used correctly, are effective. Plug-in suppressors with very high ratings are readily and cheaply available. In the US you should only buy suppressors listed under UL1449. UL tests include a testing to at least a minimum floor of protection. UPSs with surge protection should also have UL1449 listing.
========== If there is a strong surge on power wires, with no power service suppressor, at about 6kV there is arc-over from the hot busbars to the service panel enclosure. After the arc is established, the arc voltage is hundreds of volts. Since the enclosure is connected to ground-neutral-earthing electrode, most of the surge energy is dumped to earth. A surge is a short event, thus a relatively high frequency event. The impedance of the branch circuit greatly limits the current to a plug-in suppressor (unless the branch circuit is very short) and thus limits the energy that can reach a plug-in suppressor. For both these reasons the energy dissipated in a plug-in suppressor is surprisingly small.
Neither service entrance or plug-in suppressors work by absorbing the surge energy. But in the process of protecting, some energy is absorbed.
-- bud--
Most commercial telecom kit has MOVs but some high end gear has gas discharge surge suppressors.
Once in a while I've found answering machines with something resembling a neon bulb where the line lead connects to the PCB.
residence, and they're
MOVs to short out line
it to 600 volts or
device is located. This
conductors.
off what the phone like
hundreds of feet or
outlets and a phone line.
surges at the best
ground/nuetral bonding point not
fraction of an ohm.
same time actually test
oven or whatever at and
and test that same
your ground is really
actually running real
"looks good" really
boxes connected with
The lab NIST uses is not the typical home people live in.
Have you opened a "surge supressor" that the average person owns? It's really surprising more don't catch on fire with no surges.
the construction quality tends to really really suck.
Even "name brand" items from tripp-lite are utter pieces of crap for the most part. I've seen those catch fire, and these were made in USA ones.
I don't use or trust cheap-o power strips, at all, anywhere.
residence, and they're
MOVs to short out line
clamp it to 600 volts or
device is located. This
conductors.
off what the phone like
hundreds of feet or
outlets and a phone line.
clamp surges at the best
ground/nuetral bonding point not
fraction of an ohm.
same time actually test
oven or whatever at and
and test that same
load, your ground is really
actually running real
"looks good" really
boxes connected with
I have no idea what you are talking about. The discussion is ordinary surge suppressors
So don't get "cheap-o power strips". I use name brand suppressors with high ratings.
UL1449 has, since 1998, required thermal discoinnects for overheating MOVs. If a suppressor is UL1449 listed there is not much probability of any problem. The author of the NIST guide has written "In fact, the major cause of [surge suppressor] failures is a temporary overvoltage, rather than an unusually large surge". TOV is, for example, a distribution wire falling onto the secondary wires that go to your house.
-- bud--
residence, and they're
MOVs to short out line
clamp it to 600 volts or
device is located. This
conductors.
off what the phone like
not hundreds of feet or
outlets and a phone line.
clamp surges at the best
ground/nuetral bonding point not
extra fraction of an ohm.
same time actually test
oven or whatever at and
and test that same
load, your ground is really
actually running real
"looks good" really
junction boxes connected with
yes, ordinary surge surpressors. go to the store, pick one up and tell me what you find inside of it.
I'd be pleased to counter with the CPSC recall notice.
Again, if you really trust any UL markings on a power strip, go for it.
You do relized that UL doesn't even test most stuff, they sell stickers. That's the business model. If you want to get more technical, they're really a licensing company.
they have nothing at all to do with safety, at all, any more than iso 9001 has anything to do with quality.
It's possible you have some decent surge protectors, but you're 0.01% of the market.
residence, and they're
MOVs to short out line
clamp it to 600 volts or
that device is located. This
conductors.
way off what the phone like
not hundreds of feet or
outlets and a phone line.
clamp surges at the best
ground/nuetral bonding point not
extra fraction of an ohm.
same time actually test
oven or whatever at and
cables and test that same
load, your ground is really
actually running real
"looks good" really
junction boxes connected with
Complete nonsense.
In Europe equipment is mostly self-certified that it meets a standard.
UL tests almost all equipment it lists.
Some equipment, like TVs are tested to fail safely - it is not practical to test whether they work.
Much of the UL listed equipment - fuses, circuit breakers, switches, ...
- are tested to comply with a standard that requires ?fitness for a given use? and ?service life?.Ordinary wall switches used in power wiring are tested by UL to remain functional after 30,000 operations at or above their current and voltage rating. (The test is a lot more involved than that.)
For surge suppressors, under UL1449 suppressors are tested by UL for let-through voltage under specified conditions followed by a series of
20 surges followed by a let-through voltage test again. If the second let-through voltage dropped significantly the MOVs are deteriorating. A suppressor has to be functional through all these tests. Further tests are of a nature that the suppressor might fail. It must fail safely. As in my last post, overheating MOVs must be disconnected safely.Incidentally, I was the technical end of a UL panel shop.
UL listing of electrical equipment has everything to do with safety.
UL1449 listed suppressors have been tested to pass at least a minimum floor of protection. Anyone can buy well known name brands and get suppressors with high ratings like I do.
Francois Martzloff was the surge expert at the US-NIST and wrote the NIST guide. He also has many published papers on surges. I have included some of his information in previous posts.
In one of his papers Martzloff has written "in fact, the major cause of [surge suppressor] failures is a temporary overvoltage, rather than an unusually large surge". TOV is, for instance, a distribution wire dropping onto the wires that go to your house. (This is, of course, not a surge.)
Martzloff also suggests in the NIST guide that most equipment damage is from high voltage between power and cable/phone wires. (This is illustrated in the IEEE guide starting pdf page 40.)
The IEEE is the largest association of electrical and electronic engineers in the US. The IEEE guide (a link was provided) was written by the IEEE committee that covers surge protection devices. The IEEE guide says plug-in suppressors are effective. The only 2 examples of protection in the IEEE guide use plug-in suppressors.
Similarly, surge expert Martzloff says in the NIST guide (link provided) that plug-in suppressors are effective.
Where is your source that says otherwise.
-- bud--
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