Understanding Surge Protector Specs: A Guide for the Computer Age

[kiki_danc]

Can anyone prove that clamping voltage is related to surge current rating? I think it's primarily connected to MCOV only.. the following is a background brief about it from a GE SPD page:

http://apps.geindustrial.com/publibrary/checkout/DEQ-155?TNR=FAQs|DEQ-155|PDF&filename=DEQ-155 - SPD FAQs.pdf

"What are some of the pitfalls when comparing clamping
voltage ratings between SPD manufacturers?

A: The task of comparing clamping (let-thru) voltage ratings
between SPD manufacturers’ published data, may initially
be perceived as a routine process. However, clamping
voltage can be one of the more ambiguous of all SPD
ratings. In simplifi ed terms, SPD clamping voltage can be
defi ned as the peak let-through voltage the SPD will allow
for a given surge test wave. Most SPD manufacturers will
publish average clamping performance data for their
various design types, and almost all will publish this data
while referencing one or more of the surge test waves
that are defi ned in IEEE Standard C62.41. While the reference
to C62.41 is valid, it sometimes leads customers
and specifi ers to believe that IEEE 62.41 is a standard that
provides a defi nitive testing methodology for the purpose
of determining SPD performance ratings. Unfortunately,
this is not the case, as IEEE C62.41 only defi nes the
surge environment and suggested test waveforms for
the various surge risk locations. The absence of a uniform,
industry accepted test plan leads to a variety of testing
methods that can be as unique as the manufacturers
themselves. For instance, some manufacturers may
measure the clamping voltage directly at the connecting
terminals of the SPD, whereas others might measure
with 6” or even longer leads. Others may omit critical
components such as an integral disconnect or fusing.
Any one of these practices can dramatically affect test
results. When comparing clamping voltage data, it is
always a good idea to request certified reports that
describe the construction of the test samples and detailed
testing methodologies. This will provide a better understanding
of expected performance when comparing
SPD types."

Tom, what do you think? I was thinking of using the Line 1 and Neutral lead of the Siemens to connect to the transformer 120v output to make use of the 150Vac.. but I forgot the Line 2. If it would not be connected then the unit would keep alarming.. so I guess this option may not work. Is there no way to trick the unit into using Line 1 and neutral leads only?

But if I can find technical literature and proof that clamping voltage is dependent on surge current rating, then surely I'd just get the 5kV type 3 only but then transformer from 220v to 110v is still required isn't it?

Does this mean for those countries with 220volts.. they always use 110v step down transformers in the equipment to get lower clamping voltage?

 

[kiki_danc]

Tom and other EE. I have spent 1.5 hours googling for the reference that VPR is controlled by surge current rating but can't seem to find it.. for example the following are bonafide type 3 device:

https://www.leviton.com/en/docs/Q-655G_Surge_Protective_Devices_BR.pdf

You will notice that the VPR are all the same.. Notice the 36kA has even higher VPR of 700V compared to the 84kA 600V. This when pulsed with a surge of 6000Volts and 3000 ampere UL 1449 third edition test vector..

So I'll wait for your comment first about theoretical arguments why VPR may still be related to surge current capacity rating. Maybe if the pulse is only 2000 volts and 300 ampere, the clamping voltage of lower current surge capacity will be lowered? Is there proof for this?

This is the most important variable before I decide whether to get a low surge capacity type 3 or moderate surge capacity type 2 to be put at equipment. The reason I prefer type 2 at equipment is because only quality brands have type 2 SPD and thoroughly tested while most type 3 amazon power strips are not quality tested well enough.

 

[jim hardy]

So I'll wait for your comment first about theoretical arguments why VPR may still be related to surge current capacity rating. Maybe if the pulse is only 2000 volts and 300 ampere, the clamping voltage of lower current surge capacity will be lowered? Is there proof for this?

Surge testing in my day was done using a source with specific impedance that delivered a decaying sinewave voltage surge
about 1973 it was simply called IEEE SWC ---- probably it's what became ANSI C37.90 ?
anyow the surge voltage could force a calculable current through that impedance
so perhaps my basic understanding of the question at hand is warped by old prejudices.
Volts is Joules per Coulomb
so
to get from a Volt rating to the Joule rating of a suppressor
one would have to multiply Volts by Coulombs and he'd wind up with Volt-Amp-Seconds = Joules.

Amps will likely be not straightforward to calculate

Trying to relate a voltage rating to current i think would require some knowledge of the source impedance assumed, and I'm as yet unfamiliar with the present day standards and how they were derived.

I do know the 1970-ish IEEE SWC of my day came about when solid state first made its way into switchyard protective relaying.
As you can imagine, interrupting kiloamps makes large di/dt transients hence significant dΦ/dt transients,
and those dΦ/dt 's induce amazing transient voltages in the wires that interconnect protective relaying.
But since they're coupled through air the 'source impedance' is considerable.
So IEEE actually went out to some switchyards, measured some transients,
and came up with a "IEEE SWC Test Generator" that produced similar voltage and current waves typical of those they'd captured ..
Here's a description from my day

Control Technology International, Inc.
15468 East Hinsdale Circle
Centennial, Colorado 80112-4225 USA
Phone: (303)-400-0547 Fax: (303)-400-0571 Toll Free: 1-888-CTII-USA
WorldWideWeb: www.ctii-usa.com Email: ctii@ctii-usa.com

The Oscillatory and Fast Transient (SWC) Test Specifications2.2 Oscillatory (SWC) Test Wave Shape and Characteristics. The oscillatory SWC test wave is an oscillatory wave, frequency range of 1.0 MHz to 1.5 MHz, voltage range of 2.5kV to 3kV crest value of first peak, envelope decaying to 50% of the crest value of first peak in not less than 6 ms from the start of the wave. The source impedance shall be from 150 to 200W. The test wave is to be applied to a test specimen at a repetition rate of not less that 50 tests per second for a period of not less than 2.0 seconds. (All voltage and time values refer to the open circuit condition of the generator.)2.3 Fast Transient (SWC) Test Wave Shape and Characteristics. The fast transient SWC test wave is a unidirectional wave. Its rise time, from 10 to 90 % shall be 10 ns maximum. The crest duration above 90% shall be at least 50 ns. The decay time, from crest to 50% of crest value, shall be 150 ns +/- 50 ns. The crest voltage is between 4kV and 5kV, open circuit. The source impedance during the initial rise time is 80 ohms or less. The test wave is applied for not less than 2 seconds at a repetition rate of not less than 50 pulses per second. Pulses of both polarities are to be applied. (All voltage and time values refer to the open circuit condition of the generator

That's just me refreshing the old gray cells . I still have pages of your thread to digest.
Meantime i found and saved this presentation to get myself more current(no pun intended) on the subject
file:///C:/Users/Owner/Downloads/IEEE%20Surge%20Protection%20Presentation.pdf

EDIT SOURCE - beware, this stupid IEEE link doesn't open a page , it directly downloads the presentation to your C drive without asking !

perhaps some of you IEEE members can access the standards it references.
and tell IEEE for me
"Gentlemen do not write on other gentlemen's computers without permission!"

So while i know this post hasn't really contributed to the thread , and i apologize for that

thanks for tolerating an old guy trying to get himsellf up to where he can help. I've jotted down the links here for my own reference but if they help anybody else I'm overjoyed.

Been a lot of progress in the last fifty years, i'd say. I have miles to go before i speak on this topic...

http://apps.geindustrial.com/publibrary/checkout/DEQ-155?TNR=FAQs|DEQ-155|PDF&filename=DEQ-155 - SPD FAQs.pdf

emphasis mine - jh
Q: What are some of the pitfalls when comparing clamping voltage ratings between SPD manufacturers?
A: The task of comparing clamping (let-thru) voltage ratings between SPD manufacturers’ published data, may initially be perceived as a routine process.
However, clamping voltage can be one of the more ambiguous of all SPD ratings.
In simplified terms, SPD clamping voltage can be defined as the peak let-through voltage the SPD will allow for a given surge test wave.
Most SPD manufacturers will publish average clamping performance data for their various design types, and almost all will publish this data while referencing one or more of the surge test waves that are defined in IEEE Standard C62.41

What I'm taking away from this is the science of surge protection is still largely empirical.

 

[Tom.G]

Yes. Connect the Neutral lead of the FS140 to the wire that goes to the Grounded secondary terminal of the transformer. The Line leads of the FS140 get connected together then to the wire that goes to the other transformer terminal. And of course the FS140 Ground wire goes to your newly installed Safety Ground.

If you connect line 1 and line 2 of the Siemens to the 2 output of the transformer.. then the MCOV would still be 300Vac.. it's too high for 120 volts output... to force it to use the 150Vac MCOV MOV... the line 1 and neutral must be connected to the output of the transformer.. why can't this be done? This is to make sure you only have 150Vac MCOV used...

this was why I was asking how do you connect the Siemens to the transformer t to make use of the one 150Vac MOV only. if you will connect the line 1 and line 2 to the transformer output of 120 volts..

Read the bolded parts above. They all say the same thing.

Of course if type 3 with lower surge current indeed have lower clamping voltage.. then of course i'll get a type 3

Read the specs for the type 2 and the type 3 and compare the clamping voltages at the same currents, then make your decision.

Cheers,
Tom

 

[kiki_danc]

Read the bolded parts above. They all say the same thing.

Yesterday I was analyzing this sentence of your for half an hour "Yes. Connect the Neutral lead of the FS140 to the wire that goes to the Grounded secondary terminal of the transformer. The Line leads of the FS140 get connected together then to the wire that goes to the other transformer terminal."

So let me take this opportunity to clarify. When you said "The Line leads of the FS140 get connected together".. did you mean Line 1 and Line 2 are shorted together and connected to one lead of the secondary.. while the other lead is connected to neutral (and the center lead to ground)? But won't the Siemens sound fault alarm if line 1 and line 2 are shorted??

Read the specs for the type 2 and the type 3 and compare the clamping voltages at the same currents, then make your decision.

Cheers,
Tom

Clamping voltage seems to be the same for type 2 and type 3 given the same pulse of 6000V and 3000Ampere. I'm looking for a theoretical justification. Anyway I think the best power strip in amazon is this:

https://www.amazon.com/gp/product/B0009K66KY/?tag=pfamazon01-20

The spec is in the message earlier. It passed UL third edition test. So if the Siemens would detect fault if line 1 and line 2 is shorted like you asked, then I guess the solution would be this power strip to make use of the line to neutral MOV... the strip won't sound alarm. This is because I can't find individual MOV module like prosurge which is made in china.

 

[kiki_danc]

Yesterday I was analyzing this sentence of your for half an hour "Yes. Connect the Neutral lead of the FS140 to the wire that goes to the Grounded secondary terminal of the transformer. The Line leads of the FS140 get connected together then to the wire that goes to the other transformer terminal."

So let me take this opportunity to clarify. When you said "The Line leads of the FS140 get connected together".. did you mean Line 1 and Line 2 are shorted together and connected to one lead of the secondary.. while the other lead is connected to neutral (and the center lead to ground)? But won't the Siemens sound fault alarm if line 1 and line 2 are shorted??

Let me illustrate the above with the following image:

Maybe you meant connecting L1 and L2 of the Siemens to L1 and L2 of the transformer secondary and connecting the neutral to the center tap??

But then the MOV that would be engaged in the Siemens would be two 150Vac Mov making up 300Vac... so using it for 120 volts would produce too high clamping voltage.. I was asking if you could connect the L1 of the Siemens to the L1 of the transformer secondary and neutral of the Siemens to L1 of the transformer secondary?? That way you can engage only one 150Vac MOV of the siemens L-N connection.

Clamping voltage seems to be the same for type 2 and type 3 given the same pulse of 6000V and 3000Ampere. I'm looking for a theoretical justification. Anyway I think the best power strip in amazon is this:

https://www.amazon.com/gp/product/B0009K66KY/?tag=pfamazon01-20

The spec is in the message earlier. It passed UL third edition test. So if the Siemens would detect fault if line 1 and line 2 is shorted like you asked, then I guess the solution would be this power strip to make use of the line to neutral MOV... the strip won't sound alarm. This is because I can't find individual MOV module like prosurge which is made in china.

 

[kiki_danc]

Tom. Since you only surf a few moments in the evening.. let me ask this now so I can decide whether to get this:

If you really meant connecting L1 and L2 of the Siemens to L1 and L2 of the transformer secondary and connecting the neutral to the center tap (right?) as detailed in the message prior to this. Then there is this problem of using total of 150Vac+150Vac MOV since L1 to L2 in the siemens is 300Vac. I only want to use 150Vac MOV across L1 and L2 of the 220v to 110v step down transformer. Would the following work?

That is. The L(ine) of the Leviton power strip would be connected to L1 of the transformer secondary and the N(eutral) of the Leviton power strip would be connect to L2 of the transformer secondary (while the ground is either left hanging or connected to future ground line).. would this work?? Can this trick the L-N of the Leviton power strip to connect to L1 and L2 of the transformer secondary to limit it to 150Vac MOV across the 120 volts secondary transformer output? If yes. Then I'd buy this since the Siemens split phase circuit may not be tricked. Thank you.

 

[Tom.G]

did you mean Line 1 and Line 2 are shorted together and connected to one lead of the secondary.. while the other lead is connected to neutral

Yes.

(and the center lead to ground)?

What center lead?

But won't the Siemens sound fault alarm if line 1 and line 2 are shorted??

Unlikely from the product description

Regarding the Leviton 5100-PS you found at Amazon:
If you are comfortable with the 600V VPR its as good as any. If you are interested in 330V VPR look at the TSFA6A120V here: https://www.erico.com/part.asp?part=TSF6A120V
One reference I ran across (can't find it now) is the lowest UL rating is 330V, then in goes up 400, 500, 600...

Tom. Since you only surf a few moments in the evening..

Not quite so, more like 4+ hours; most of it lately looking up data for, or explaining to, you!

More to follow...

 

[kiki_danc]

Yes.What center lead?

.

The black wire in the center... but then if you short the L1&L2 of the Siemens leads and connect it to one of the blue leads.. then what do you connect to the 2nd blue lead? This was what I was trying to figure out yesterday for an hour.

Unlikely from the product description

Regarding the Leviton 5100-PS you found at Amazon:
If you are comfortable with the 600V VPR its as good as any. If you are interested in 330V VPR look at the TSFA6A120V here: https://www.erico.com/part.asp?part=TSF6A120V
One reference I ran across (can't find it now) is the lowest UL rating is 330V, then in goes up 400, 500, 600...

Oh.. I'd get the erico then.

Not quite so, more like 4+ hours; most of it lately looking up data for, or explaining to, you!

More to follow...

Thanks so much.

 

[jim hardy]

Edited source for that informative IEEE Surge presentation in post 143 , see cautionary note

 

[Tom.G]

Edited source for that informative IEEE Surge presentation in post 143 , see cautionary note

Hey Jim, it says 'download' in the link. Thanks for the heads-up!

 

[Tom.G]

The black wire in the center... but then if you short the L1&L2 of the Siemens leads and connect it to one of the blue leads.. then what do you connect to the 2nd blue lead? This was what I was trying to figure out yesterday for an hour.

That's an 18VCT transformer though.

Here is what I was trying (un-successfully) to describe in words.

 

[kiki_danc]

That's an 18VCT transformer though.

Here is what I was trying (un-successfully) to describe in words.

View attachment 231767

But we were talking about the split phase Siemens with 2 Line 1 and Line 2, and neutral and ground. I'm still confused how do you connect it to the transfomers? pls use the following image instead.. thanks.

After your reply. I'd know all and can already decide. Thanks.

 

[Tom.G]

Those drawings take me For-ever!
Just connect the L1 and L2 together and treat them as the Line in the post #152 drawing with the outlet strip. The Neutral and Ground also connect as shown there.

 

[kiki_danc]

Those drawings take me For-ever!
Just connect the L1 and L2 together and treat them as the Line in the post #152 drawing with the outlet strip. The Neutral and Ground also connect as shown there.

Ok. I got it. So you short L1 and L2 together and connect them to one transformer secondary terminal. While the 2nd terminal of transformer secondary is connected to neutral, and ground to transformer ground wire. Ok. I'd order the Siemens 140,000 at amazon now. It's the best type 2 surge protector in the market. I'd put it in the main panel breaker as type 2 in parallel with my existing 50,000A prosurge surge protector. then get the erico as type 3. I guess this would produce the best of all worlds.. so many thanks to you Tom and others. :)

 

[kiki_danc]

Tom. Jim still couldn't understand why I'd try to tap 120 volts to neutral in my country since he didn't have time to read our 9 pages of surge protection thread. So I need to know the following as finishing touch since you understand the context.

To avoid using transformers in the equipment for type 3 surge protection, I can just tap the Line to Neutral in my main panel for one particular breaker to the security equipment.

If you use the neutral of one subpanel as ground for the aircon metal casing (top subpanel).. while for another panel (bottom subpanel).. you use the neutral as conduit for line 1 (that is, line to neutral to get 120 volts service like in your country).. would the neutral in the top subpanel you are using as ground gets electrified? What would be the danger of combining it?

 

[Tom.G]

you use the neutral as conduit for line 1

I don't understand what that means. Must be your turn to draw a picture showing details.

In the drawing, there is some text "NEUTRAL CONNECTED TO LINE 1". If I take that literally, it leads to BIG sparks, and tripped circuit breaker; it's called a "Short Circuit".

 

[kiki_danc]

I don't understand what that means. Must be your turn to draw a picture showing details.

In the drawing, there is some text "NEUTRAL CONNECTED TO LINE 1". If I take that literally, it leads to BIG sparks, and tripped circuit breaker; it's called a "Short Circuit".

What I mean to say is. The equipment would be connected to Line 1 and neutral so I can use 120 volts surge protector type 3 without using transformer as you suggested earlier in the thread.. of course you won't short it.. mistake in the drawing :)

 

[jim hardy]

I asked the same question.

See my post #12 over at tripping thread.. https://www.physicsforums.com/threads/tripping-behavior-of-circuit-breakers.956954/#post-6067795

 

[kiki_danc]

What I mean to say is. The equipment would be connected to Line 1 and neutral so I can use 120 volts surge protector type 3 without using transformer as you suggested earlier in the thread.. of course you won't short it.. mistake in the drawing :)

This is the correct illustration: :)

 

[Tom.G]

What I mean to say is. The equipment would be connected to Line 1 and neutral so I can use 120 volts surge protector type 3 without using transformer as you suggested earlier in the thread.. of course you won't short it.. mistake in the drawing :)

We already covered that in the discussion about the security system. Safe and effective surge suppression is not directly compatible with your electrical system. Forget it! Use a transformer.

 

[kiki_danc]

We already covered that in the discussion about the security system. Safe and effective surge suppression is not directly compatible with your electrical system. Forget it! Use a transformer.

Yeah. It's the best then because if given the option to ground the building appliances (use the neutral as grounding) or use optimum surge protectors (120 volts without transformers). Then I'd choose grounding anyday because electrocution is worse than having fried computer you can replace. You can't replace a fried body :)

Well. For most of our office building with already neutral wires that aren't used (because we used line to line of 240 volts) only. Our neutral is our ground. It would be too costly to make separate ground wires because you have to redesign the entire building and it's no longer possible when it's fully constructed.. hence the least thing is to make our neutral wires as ground (by adding rods to Earth and connecting this to the neutral at main panel) as you described earlier. Unfortunately. We can no longer dig 8 feet of ground to insert the rods because the floor is already cemented with tiles. In case like this.. then the only option is to use the neutral to connect to metal enclosure.. at least it can trip the breakers if hot lines get into contact with the enclosure.

 

[Tom.G]

There are drills made to put holes in concrete. Here in the US the Grounding is often done at the enclosure for the electric meter (they are usually outdoors) and then carried thru to the breaker box with the power wires.

If you decide to add a Ground, make sure it is legal and safe to do before attempting it.

 

[kiki_danc]

There are drills made to put holes in concrete. Here in the US the Grounding is often done at the enclosure for the electric meter (they are usually outdoors) and then carried thru to the breaker box with the power wires.

If you decide to add a Ground, make sure it is legal and safe to do before attempting it.

Maybe adding those ground rods can minimize those electrical jolts in my concrete ceiling.. isn't it.. but can't we rely on the power utility Pole ground since neutral in the pole is already connected to the ground at soil (i'll confirm if my pole indeed ground its neutral).

 

[Tom.G]

Any ground at the pole is obviously not the same as your Neutral, you wouldn't get a shock if it was!

 

[kiki_danc]

Any ground at the pole is obviously not the same as your Neutral, you wouldn't get a shock if it was!

If all my neutral were connected to the breaker panel and it is connected to the pole and then to ground, you mean we won't get any shock?

Hmm... then I wonder where the shocks came from. If I'd hire electrician... I wonder how he would start since my panel were all properly connected... If hot wires are touching the concrete.. won't this trip the breaker? Maybe there is low threshold short from hot wire to concrete.. this is possible?

 

[Tom.G]

If hot wires are touching the concrete.. won't this trip the breaker? Maybe there is low threshold short from hot wire to concrete.. this is possible?

Trip the breaker --- probably not
short from hot wire to concrete.. possible --- yes

 

[kiki_danc]

As we came to the close of our discussions. Time for some bit of reflection. I wonder how many of you really use surge protectors. I have IBM XT that is still working even though I don't have a surge protector for 30 years. For some, surge protectors may be like nit picking, isn't it. I just need one now to protect a $1500 fire panel system with 30 smoke detectors.. but it's been on for a year without damage... so my inquiry into surge protectors is partly to gain more understanding of things electrical. Here I learned of the importance of proper grounding, etc.

 

[kiki_danc]

Trip the breaker --- probably not
short from hot wire to concrete.. possible --- yes

Locally I'm being quoted for $400 for the Erico TSF6A120V (the only 330V clamping voltage UL 1449 4th edition strip surge protector in the planet?). Crazy price. I think I'll find a way to order it right at USA where it could be just below $100. If you find the micro physics how clamping voltage is related to surge current rating.. please let me know because I can't find any reference that explains the link. Thank you.

 

[kiki_danc]

Yes.What center lead?Unlikely from the product description

Regarding the Leviton 5100-PS you found at Amazon:
If you are comfortable with the 600V VPR its as good as any. If you are interested in 330V VPR look at the TSFA6A120V here: https://www.erico.com/part.asp?part=TSF6A120V
One reference I ran across (can't find it now) is the lowest UL rating is 330V, then in goes up 400, 500, 600...

The 330V is from here: https://www.ewh.ieee.org/r3/atlanta/ias/IEEE_Meeting_SPD_Standards.pdf I wonder if those countries that use 220 volts electricity also use step down transformer 220V-110V to get lower clamping voltage by using 150Vac SPD. Anyone knows?

Not quite so, more like 4+ hours; most of it lately looking up data for, or explaining to, you!

More to follow...

 

[Tom.G]

If you find the micro physics how clamping voltage is related to surge current rating.. please let me know because I can't find any reference that explains the link.

Please take into account that a type 1 SPD typically has a very high surge current rating and a higher clamping voltage than a type 3 of the same MCOV. This may not be an inherent characteristic of the MOV, but just a design decision of the SPD manufacturers.

We were probably thinking in slightly different contexts, but here are a couple examples of voltage rising with increasing current. I was mostly referrring to similiarly sized hardware that may be rated somewhat differently by different manufacturers.

http://www.ijeee.net/uploadfile/2016/0316/20160316114821550.pdf

 

[kiki_danc]

Please take into account that a type 1 SPD typically has a very high surge current rating and a higher clamping voltage than a type 3 of the same MCOV. This may not be an inherent characteristic of the MOV, but just a design decision of the SPD manufacturers.

Won't Type 2 SPD with high surge current rating and low clamping voltage be more advantageous.. I wonder why all manufacturers won't design it that way.. unless it's more expensive to design low clamping voltage?

We were probably thinking in slightly different contexts, but here are a couple examples of voltage rising with increasing current. I was mostly referrring to similiarly sized hardware that may be rated somewhat differently by different manufacturers.

http://www.ijeee.net/uploadfile/2016/0316/20160316114821550.pdf

View attachment 231777

 

[kiki_danc]

The 330V is from here: https://www.ewh.ieee.org/r3/atlanta/ias/IEEE_Meeting_SPD_Standards.pdf I wonder if those countries that use 220 volts electricity also use step down transformer 220V-110V to get lower clamping voltage by using 150Vac SPD. Anyone knows?

View attachment 231775

By the way, the Erico 330V clamping voltage SPD model has only Imax of 20kA (nominal of only 3kA). I wonder what would happen if say a 30kA surge cross it? Would the MOV be damaged or just ignore that higher transient than it's capacity? For voltage.. anything higher than the MCOV can short and shorten the lifespan of the MOV. I wonder what higher transient than capacity would behave? Got any idea?

 

[Tom.G]

Won't Type 2 SPD with high surge current rating and low clamping voltage be more advantageous.. I wonder why all manufacturers won't design it that way..

Staged Protection. http://lit.powerware.com/ll_download.asp?file=SA01005003E_150dpi0607.pdf

I wonder what higher transient than capacity would behave? Got any idea?

Used to be would short the MOV and trip the breaker, these days many (most?) of the SPDs built into outlet strips come with built-in fuses to disconnect the MOVs when they short. This sometimes stops the breaker tripping but disables the protection, as indicated by the little red Idiot Light labeled "PROTECTED" not being illuminated.

By the way, an SPDs lifetime is one full-rated surge. It is a sacrificial device, cheaper than the equipment it protects. Lifetime increases with smaller surges.

 

[kiki_danc]

Staged Protection. http://lit.powerware.com/ll_download.asp?file=SA01005003E_150dpi0607.pdf

Used to be would short the MOV and trip the breaker, these days many (most?) of the SPDs built into outlet strips come with built-in fuses to disconnect the MOVs when they short. This sometimes stops the breaker tripping but disables the protection, as indicated by the little red Idiot Light labeled "PROTECTED" not being illuminated.

I was asking about surge current. I know higher surge voltage can short the MOV.. But maybe you also mean if the surge current is say 30kA, it can also short the 20kA SPD even if the surge voltage is below the MCOV of say 320Vac?

By the way, an SPDs lifetime is one full-rated surge. It is a sacrificial device, cheaper than the equipment it protects. Lifetime increases with smaller surges.