Re: belkin power conditioner for my Samsung LCD - is it worth it???

phil-news-nospam@xxxxxxxx wrote:
On Tue, 07 Aug 2007 15:33:21 -0500 bud-- <remove.BudNews@xxxxxxx> wrote:



|> In most cases.
| | Everything I have read is that plug?in suppressors with high ratings | have a high probability of protecting equipment that is properly | connected to it. Even better with a service panel suppressor and single | point ground.
| | Exception such as?

If a full direct strike comes in on the power line (rare, but it happens)
it could very well be in common mode. The plug in power strip style
protectors won't have anywhere to divert the lightning. This is where
the entrance protectors talked about are needed. They need to be close
to the ground connection so more of the lightning goes that way.

The N-G bond at US services turns common mode surges on the power line into differential mode surges.

But that doesn’t matter. As I have said more than once, the IEEE guide explains that plug-in suppressors work by clamping the voltage on all wires (power and signal) to the common ground at the suppressor. They do NOT work primarily by earthing the surge. The guide explains that the NEC does not intend for surges to be earthed on the ground wire of a branch circuit. In the IEEE guide example starting pdf page 40, almost all the earthing of the surge coming in on the CATV drop is through the ‘ground’ wire from the CATV entry block to the power service.

Plug-in suppressors do NOT work primarily by diverting lightning. You have not figured out how they do work.

A surge suppressor at the power service is a good idea. If there is none, there will be arc-over at panel (and receptacles) at about 6,000V. That is why the 2nd Martzloff paper has a spark gap at the source. The ‘clamp voltage’ of the arc is likely a lot lower than 6,000V. The arc will dump most of the surge energy to earth. The branch circuit impedance will greatly limit the current to a plug-in suppressor.



| ---------------
| Fran?ois Martzloff was the NIST guru on surges until he recently | retired. He wrote the NIST guide as well as may technical papers including:
| http://www.eeel.nist.gov/817/pubs/spd-anthology/files/Neutral%20earth...
| "The Effect of Neutral Earthing Practices on Lightning Current | Dispersion in a Low-Voltage Installation"
| | One of the test scenarios was a US system with 3 buildings connected by | separate service drops to a single transformer. All 3 houses had | service panel surge suppressors. One of the houses was hit with a | 100,000A surge with rise time of 10 microseconds and duration of 350 | microseconds. This is a large hit with a very long duration. The hit | was to the neutral service connection at the house. In total this is | close to a worst possible case.
| | *1* The result was
| 21,000A was conducted to earth at the building (this lifts the ground | potential at the house)
| 33,000A flowed away from the building on the service neutral to the | transformer and other 2 buildings
| 23,000A went through each of the hot-neutral protectors and flowed away | from the building on each hot service conductor to the transformer and | other buildings.
| | 2 of the 3 service panel surge protection devices had a peak current of | 23,000A
| | The dissipation at the building surge protector was 3500J
| | *2* If the same surge hit one of the other buildings the dissipation | at the surge protectors at this building was 840J.
| | *3* If the surge was shorter - 20 microseconds - which is probably | more realistic, the surge suppressor dissipation would be 200J, or if | the hit was to one of the other building the surge protector | dissipation at this building would be 80J
| | For comparison, the *plug-in* surge protector I recently bought had | rating between each pair of wires of 30,000A and 590J (1180J for both | hots to ground). But my plug-in protector was rated at a higher current | than occurred in any case, and the energy rating was higher than | occurred except the strong hit the building (*1*). Service panel | protectors would likely be rated higher. And this is near worst case.
| | A service panel suppressor can survive a very near hit. A plug-in | suppressor could provide additional protection, particularly for high | value ?2-link? devices.

Just because one device alone cannot provide complete protection is not
a reason to remove it. The more protection you have, the better. But
you need to _start_ would having proper entrance protections so other
devices only have to protect against secondary surges (a portion of the
main surge that doesn't all get diverted due to things like induction
in the path).

Protection is always a trade-off of - degree of risk - value of what you are protecting - cost of protection.

If I lived in central Florida I would make sure I had:
a good earth connection
a good “single point ground”
a high rating service panel suppressor
a high rating plug-in suppressors on high value equipment (primarily 2-link) like HDTV and computer (not so much because of computer value as value of the date).

If I lived in Nevada, I would probably concentrate on the plug-in suppressors.

What I have read, including the guides and the 2 Martzloff papers, indicates even without service panel suppressors, plug-in suppressors with high ratings connected properly are very likely to protect against all but very near strikes.



| -----------------------------------------------------------
| Another Martzloff paper looks at a MOV (simulating a plug-in suppressor) | at the end of a 10-50 meter branch circuit. The surge is 2,000-10,000A, | and I believe 25 microseconds. There is no (service panel) suppressor at | the source but there is an arc-gap at the source end with a breakdown | voltage of 6,000V, which duplicates arc-over at the service panel.. | Arc-over dumps a large percentage of the surge to earth. Branch circuit | impedance greatly limits the surge current to the MOV at the end of the | branch circuit.
| | In all cases the energy dissipated at the MOV was less than 1J except | for a 10M branch circuit and, ironically, the lower current surges below | 5,000A. Contrary to intuition, at all branch circuit lengths the energy | dissipation at the MOV was lower as the surge current went up. That was | because the MOV acted to clamp the voltage at the source spark gap. With | the short branch circuit and lowest surge currents, the MOV prevented | the gap from arcing over at all. Higher current surges forced the | voltage at the gap up faster causing it to break down faster and dump | more of the energy to earth.
| | I don't remember the branch circuit current was indicated, but it would | be far below the max surge current of 10,000A. The max energy | dissipation at the MOV was 22J. Plug-in suppressors are readily | available with ratings higher.

The size of the branch circuit probably didn't matter much. The length
of the wiring mattered more.

I agree. The inductance of the wire dominates over the resistance because a surge is basically a high frequency pulse.


My concern with the plug-in suppressors is that not all the energy will
always be in differential mode.

As I said above, plug-in suppressors work for any mode surge. It doesn’t matter.

Fortunately, common mode really hates
to go very far along a wire because it gets dragged by a huge magnetic
field (or you can think of it as dragging the field along with it). But
that can induce current in a lot of unexpected places.

I've had a stereo system damaged by induced current even though it was
unplugged when the hit took place. Sufficient current was induced into
the speaker wires to destroy the amplifier final transistors (the rest
of the amp worked fine once those transistors were replaced) and melt
down the tweeter coils (the bass coils and the crossovers survived).

I don’t remember if it is one of the guides, but you can pick up radiated surge energy in wiring acting a ‘long wire’ antenna.
Or it can be picked up with wiring acting as a loop antenna - with the loop being the power wires and, for example, the phone wire - with the loop closed the ground bond at the building entrance and the voltage appearing at a computer. The orientation and area of the loop determine the pickup.



| ----------------------------
| As you probably know, service panel and plug-in suppressors do not | protect by absorbing energy, but they absorb energy in the process of | protecting.
| | MOVs have a maximum energy they can dissipate. This is the rating for a | single hit. With high energy ratings, the energy of a single hit | becomes a smaller percentage of the MOV single event rating. The smaller | the percentage is, the larger the total cumulative energy the MOV can | absorb. With small hits relative to the rated energy a suppressor | cumulative energy rating may be 10 or 50 times the single event. | ?Oversized? suppressors may never fail.
| | In addition, as described at length in the IEEE guide, the protected | load may (or may not) be connected across the MOVs. If connected across | the MOVs (preferred), the protected load will be disconnected with the | MOVs if they fail.

The MOV dissipation required is going to be figured from how much
resistance they have. The more energy it can pass to the other wire(s)
the less it needs to dissipate.

MOVs are intrinsically a voltage clamp with nonlinear resistance. The energy dissipated is the clamp voltage times the surge current times the surge duration (time). The energy hit is substantially fixed by the clamp voltage rating and the actual surge current.



| ---------------------------
| In another guide Martzloff said "In fact, the major cause of TVSS [surge | suppressor] failures is a temporary overvoltage, rather than an | unusually large surge."

The "swell". I wonder just how much that overvoltage was. With clamp
voltages of 330 volts, an RMS of 240 volts, like you might get if you
take it over to UK and plug it in there, you could see it activate on
the actual line voltage. That, or plug it into the 240 volt outlet in
the USA, putting the "L-N" MOVs on a L-L connection at 240 volts even
though each line relative to ground is only 120 volts (in USA, not UK).

“Temporary overvoltage” is typically used to describe a longer duration event than a “swell” with a “swell” up to a few seconds and “temporary over voltage up to ?. A “swell” could certainly take out a MOV depending on the current.

I expect ‘common’ overvoltage sources would be an open neutral on a service (or multiwire branch circuit) and a high voltage distribution wire dropping onto 120V secondary wires.

The 330V rating is a peak voltage. 240V RMS is equivalent to 340V peak. As a MOV starts to fail, conduction starts at a progressively lower voltage.

A few plug-in suppressors will disconnect on overvoltage. Otherwise, if the protected load is connected across the MOV, the protected load will stay protected when the MOV is disconnected on failure.


--
bud--
.

Relevant Pages

  • Re: Phone line surge protection?
    ... w_tom's assertions about plug-in surge protectors are based on knowledge ... says plug-in suppressors work primarily by CLAMPING the voltage on all ...
    (comp.sys.ibm.pc.hardware.storage)
  • Re: Linksys router + switch vs router/switch combo
    ... local power pole giving his house a surge. ... and had various results from the various surge protectors he ... That is one reason some plug-in suppressors have connected equipment ...
    (comp.sys.mac.hardware.misc)
  • Re: Surge Protectors
    ... WOuld it make sence to put a surge suppressor on my ... 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, ... UPSs with surge protection should also have UL1449 listing. ...
    (sci.electronics.repair)
  • Re: What are you using to protect your studio audio equipment from power issues?
    ... And also guide from the NIST: ... Service panel suppressors are a real good idea. ... To limit that voltage you need a *short* ... What did those plug-in protectors do? ...
    (rec.audio.pro)
  • Re: Surge Protectors
    ... WOuld it make sence to put a surge suppressor on my ... any competent plug-in suppressor manufacturer should tell you the phone wires have to go through the suppressor along with the power wires. ... Plug-in suppressors work primarily by clamping, ... UL tests include a testing to at least a minimum floor of protection. ...
    (sci.electronics.repair)