Sprecification of TVSS

[vinsa]

About TVSS specification I have a question

How are linked the size and the guarantees?

About the size in the market we can find models with "capacity" of 40, 80 or 100, 160 and maybe up to 640 Kamp /phase depending of where we want to put them A, B or C . In fact there is also a "guide" to select accordingly with the Main breaker capacity ( 60 ,100 800 , 1,600 Amperes)

I guess that internally a TVSS is composed let´S say of MOV´s in parallel, they are going to fail
(to be crossed) along its usefull life and the will gradually reduce its capability . In fact some manufactures offer a way to check the PERCENTAGE that remains till the end of the TVSS protection function.

About the guarantee if you look at the same rating model the one with more years guaranteeing is bigger ( 5 vs 20 years)

Am I correct ?

[ron]

The guarantee is a marketing idea. Compare the amps/mode. Be sure it has the modes of protection you want.
The manufacturer is planning on most folks not taking them up on the guarantee, so the years offered is marketing and a gamble by the Manuf.

[ October 16, 2003, 03:32 PM: Message edited by: ron ]

The guarantee may be pro-rated too which means if it fails within the warranty period you only have to pay for the years actually used. The remainder is only credited towards the purchase of a new unit. This locks you into continuing with their brand unless you want to forfeit the warranty credit. Again, mostly a marketing scheme. Best yet is a non-pro-rated warranty where if the unit dies within the warranty period you get a brand new unit. You don't get an extended warranty, but you do get a new item. Even this kind of warranty in a sense locks you into staying with that brand. Best to do careful shopping and buy the higher quality unit regardless of warranty. Only use the warranty as a consideration, not as the acid test.

[vinsa]

Ok Thanks

I agree about guarrantee. In fact in my experience two or three failed supresors have been changed for new ones and the only charge has been transportantion back and foth to the manufaterer

What I would like to stress is the first part of my question

Do the TVSS capacity in Kamp/phase is because they supposed to absorb " so many" spikes and they gradually are "failing" ?

Regards

[dereckbc]

MOV's will degrade with each turn-on action. What you should look for in the specs is how many ANSI Cat C3 impulses the device will survive without degration.

The better units will have SAD's as the primary device, and MOV's as a secondary device to absorb large amounts of energy. Theory is SAD's will take care of the small stuff, and MOV's for large events.

Just make sure you are looking at amps per mode and not amps per phase.

[ October 20, 2003, 04:31 PM: Message edited by: dereckbc ]

[jrdsg]

derek, you just blow me away, man.

jr

[tom baker]

With TVSS you get what you pay for.
Look for a TVSS with multiple protection methods such as MOVs and gas tubes. Also a monitoring function with a relay and alarm light to indicate failure.
don't worry about the response time.
Look at the joules and clampling voltage, and of course listing to UL 1449 Second edition.

[dereckbc]

Originally posted by vinsa:
Do the TVSS capacity in Kamp/phase is because they supposed to absorb " so many" spikes and they gradually are "failing" ?Each manufacture is different. Again look at the spec sheet and see how many ANSI Catagorie B1, B2, B3 or C1, C2, C3 Pulses were used to test without any degration. Make sure it is third party tested, and not by the manufacture.

The better units will survive 5,000 ANSI Cat C3. The cheaper units will not publish or self test.

[ October 20, 2003, 04:55 PM: Message edited by: dereckbc ]

[vinsa]

I´m searching in ANSI C 62.41 and C62.45

Accordingly with the Standard Surge Test Waveform , let say we are in a C3 High System Exposure and so we will expect a 20 KV and 10 Kamp Surge ambient.

On the other hand (I don't know exactly where)

but based on the Dereckbc comment , the best TVSS will resist 5,000 Spikes for this location

Now the question is on the SELECTION process of the TVSS how is related the "capacity" offer by some vendor let say for a 2,000 Amps distribution panel a 300 Kamp /phase model with the ANSI SPECS?

[dereckbc]

You base the size of Class C devices per your risk assesment. C3 high risk, C2 medimum risk, C1 low risk. Some manufacures do reccomend amps per mode based on service size, but ANSI bases it on risk assesment. In other words you decide. If in doubt C3 CYA.

Order based on amps per mode, ignore amps per phase. Service entrance only requires L-N modes. L-L and N-G modes are redundant at the service entrance and only raise unit cost. Also look for units that obtain their "amps per mode" with a single MOV device rather than multiple parallel MOV devices.

The best method is to use TVSS integrated into the service and sub-panels. It will eliminate installation issues that plague add-on units.

If you request I can suggest some manufactures and models.

Dereck

[vinsa]

OK Dereckbc but how relates the "amp / mode " capacity ( I have " Kamp /phase" ) with the location (C1, C2, C3)

If I may expect a C3, 10 Kamp transient that some day will hit my entrance and the vendor is saying that I need a 300 Kamp/ phase I may think is because during its useful life this TVSS may resist 30 big 10 Kamp strikes or maybe 5,000 lower spikes ( accordingly with IEEE C 62.41 or 45). Is this correct ?

Regards

[dereckbc]

The "amps per phase" is simply the theoretical addition of all the "amps per mode" on a phase. For example; lets say each mode device is rated 120KA. On each phase you have a device installed L-N, L-G, and L-L, or in other words you have three modes of 120KA each, which equals 360KA per phase. But it cannot be tested, it is a theory, the impedance is different in each mode and therby will react differently.

At a service entrance you only need L-N modes because of the N-G bond. The L-L, L-G, and N-G are redundant and only add cost. So if you are looking for a service entrance device with 300KA per phase, forget it, look for one with L-N mode only rated 300KA per mode... What a beast that would be.
Does that answer your question?

[vinsa]

Mr . Dereckbc

Thanks for all your usefull comments

I still dont know how a TVSS manufacturer RATES their products ( 360 Kamp / phase = 120 Kamp / mode ) as an example

From the user point of view I have a clear picture of how to make a good specification, refering among other things the IEEE C62.41 wave forms and the UL 1449 clamping voltages.

From the Internet I got a usefull manual issued by Leviton

The question remains

[dereckbc]

Vinsa, the proper method is "amps per mode". I assume you know this means i.e L-N mode. "Amps per phase" is the simple addition of all the modes associated with the phase.

The better manufactures will list dual ratings, one for mode, and another for phase. Just ignore the "amps per phase".

The other things to ignore are "joules" and "clamping voltages", they mean nothing as the are the indivdual component rating rather than the device rating.

You are already on the right track. Study and comprehend ANSI C62.41, ANSI C62.45, UL-1449, NEMA LS-1, and I think UL-1289. Once you understand these documents you will be able to spot the better devices with a quick glance. The key is to look in the specs and see if all the above references are made.

FYI UL-1449 is SVR rather than "clamping voltage". Two completely different ratings and is one of the keys to understanding the tricks manufacture use.

[vinsa]

OK Dereckbc , thanks

Just one question . Could you explain the difference between SVR and Clamping Voltage?

Bye the way is it possible to get the UL 1449 Standard free from the Web ?

Regards

[dereckbc]

Sure. The clamping voltage is a measure of the turn-on voltage of the Surge Protection Device (SPD) with no leads. This means that testing excluded the parasitic onductance of the SPD. Parasetic inductance is made up of the internal and external leads, connections, fuses, etc. In fact this practice could eliminate 24 inches or more of lead length from the test. Extremely mis-leading

The Suppressed Voltage Rating (SVR) is a value that is assinged by UL to indicate its protective charactristics. Each mode of the SPD is subjected to three impulses of 1.2/50us, 6kv voltage waveform and an 8/20us 500 a current waveform. The resultant measured limiting voltage, is measured at the ends of 6 inches leads extending from the terminals of an integrated product or 6 inches extending from the enclosure of a wall-mounted cabinet. Real life situations.

The ratings are:
330 or less = 330
331 - 400 = 400
401- 500 = 500
and so on.

As far as a free copy of UL-1449 Second Edition. Beats me.

[pierre]

Dereck

I am very impressed :eek: with your knowledge and the ease in which you explain it. Just how much would that info normally cost us if we had to find it on the 'street'?
I used to think I knew about SPD, you made me realize there is a lot to this!!
Thanks

Pierre

[Marlongua]

Dereck

I would like to ask your opinion about the protection systems udes by the Rayvoss unit and the common MOV´s units. And wich ones you think are the best MOV´s brands?

Thanks