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Surge Protective Device

02/02/2017 12:30 AM

Good day

Is there any performance problem if the SPD is oversized?

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#1

Re: SURGE PROTECTIVE DEVICE

02/02/2017 12:31 AM

Maybe a wallet performance problem....

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#7
In reply to #1

Re: SURGE PROTECTIVE DEVICE

02/02/2017 1:08 PM

Right on.GA

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#2

Re: SURGE PROTECTIVE DEVICE

02/02/2017 2:39 AM

yes.if you oversize an SPD so that the Vp voltage of SPD is higher than your equipment highest voltage level "Um" , then your eqipment will fail when SPD starts conduction on overvoltage. point is select an SPD with Vp less than Um of your equipment .Um are defined for different catagories of equipment from catagory I to IV . find your equipment catagory and Um , then select an SPD with Vp less than Um. hope this helps a bit.

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#11
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Re: SURGE PROTECTIVE DEVICE

02/02/2017 11:27 PM

Protective devices usually have two parameters: the voltage and the energy they can dissipate. I guess the forum thinks that this thread is about the energy, where oversizing protection is equivalent to multiple Surge Protection Devices connected in parallel.

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#3

Re: SURGE PROTECTIVE DEVICE

02/02/2017 3:12 AM

Yes, if it doesn't fit where it is supposed to be installed...

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#4

Re: Surge Protective Device

02/02/2017 6:07 AM

Not fundamentally. I usually follow the philosophy that, if it is a "one off" job and the voltage/current to be handled is uncertain; then it is better to oversize than finish up with a "failure, rethink & replace cost" known in industrial design as "Not Right First Time".

Oversizing must not mean a higher SPD working voltage (and power) which exceeds that safe for load.

Aside from cost, and space to fit it, fitting "remotely" with long leads might give excessive inductance/resistance/"cross-coupling in to out" in connecting leads.

In some cases, the higher leakage current in a high power SPD might have an effect on residual current protection before the SPD.

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#5

Re: Surge Protective Device

02/02/2017 12:09 PM

No this is common practice...it's done for longevity and dependability....

..."When a surge enters a panel, it does not care or know the size of the panel. So how do you know if you should use a 50kA, 100kA or 200kA SPD? Realistically, the largest surge that can enter a building’s wiring is 10kA, as explained in the IEEE C62.41 standard. So why would you ever need a SPD rated for 200kA? Simply stated - for longevity."...

Ref...

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#24
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Re: Surge Protective Device

02/06/2017 5:28 AM

I agree. I heard that each surge will degrade the protection. So oversizing is key to insuring the unit will remain operational after a few good surges.

To the OP, I think you should ask others in your physical area to see how "clean" the incoming power is. Some places are known to have large and frequent surges (burned out equipment), while others have very few. I believe another factor is if you have a high power user nearby. They'll cause fluctuations in your power. And watch for places with lots of lightning strikes!

I am not an expert in this field, but I'm posting things I've been told by others who are experts.

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#26
In reply to #24

Re: Surge Protective Device

02/06/2017 6:22 AM

Can someone explain why over sizing, (over design) is imperative when no one has yet established the assumed Ka that is being experienced. Protection is not cheap and going greater than is required is a foolish expense.

Is this normal line voltage surges, lightning? Factory, house, computers?

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#6

Re: Surge Protective Device

02/02/2017 12:19 PM

As others have hinted about, it depends upon your application and what you mean by "oversized", so please provide more details regarding both.

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#27
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Re: Surge Protective Device

02/18/2017 5:15 AM

By oversize i mean kA, my application is in office, VRF air-conditioners and Server's distribution boards

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#8

Re: Surge Protective Device

02/02/2017 2:42 PM

STD - you should go to the hospital and get that checked.

SPD - Site planning and design - an oversized sewer line will not provide enough water level and velocity to carry away solids, and will clog up (nastily I might add) more frequently than one that is properly sized.

Why in the 21st Century are we still doing sewer lines, and not instantly vaporizing poo back to the elements?

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#10
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Re: Surge Protective Device

02/02/2017 7:59 PM

Yes I have to agree that this is probably going to be realized soon....the prions and drugs are going to make this a necessity.....We are contaminating our food supply and our water supply, add in air pollution and you should be able to read the handwriting on the wall as they say.....

..."The human sex ratio is of particular interest to anthropologists and demographers. In human societies, however, sex ratios at birth may be considerably skewed by factors such as the age of mother at birth,[3] and by sex-selective abortion and infanticide. Exposure to pesticides and other environmental contaminants may be a significant contributing factor as well.[4] As of 2014, the global sex ratio at birth is estimated at 107 boys to 100 girls (1000 boys per 934 girls).[5]"...

We start off with more boys than girls, and end up with more girls than boys...

https://en.wikipedia.org/wiki/Sex_ratio

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#9

Re: Surge Protective Device

02/02/2017 7:29 PM

For an informed answer, use a search engine.

How to choose the right surge protector? - Schneider Electric Blog

Surge protection devices: how to choose them?

You will get opinions here, not necessarily a correct answer.

Consult a manufacturer's website.

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#12

Re: Surge Protective Device

02/03/2017 12:02 AM

Yes

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#16
In reply to #12

Re: Surge Protective Device

02/03/2017 11:34 AM

How do you mean oversized? As in fat? As in over-staffed? As in stature?

Oh and by the way, stop hiding behind that mask, Mr. AP

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#18
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Re: Surge Protective Device

02/03/2017 12:13 PM

Looks like a witch hunt going on for Anon.

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#19
In reply to #18

Re: Surge Protective Device

02/03/2017 12:23 PM

We don't witch hunt them, just hunt them. Then like a man-eater, we put them down.

Rails don't get laid down when the workers are afraid of the lions in the grass.

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#21
In reply to #19

Re: Surge Protective Device

02/03/2017 1:31 PM

That's why Ethiopia gets the Chinese to lay track and Kuwait doesn't have a railway. Too many lions and no grass.

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#22
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Re: Surge Protective Device

02/03/2017 1:36 PM

But the lions we can see are not the dangerous kind. It is always the hidden ones....those are the ones that spring up when not expected.

The real worst are the lyin' Democrats. They are the snarly beasts that eschew truth, munch on lies and innuendos, and when their hate fails to keep the undercrust in tow, they resort to name calling, tirades, stalling, and bargaining with the devil.

But for them, there would be no undercrust to keep in tow. They are the ones keeping down the masses from realizing their dreams. I hate them with a white hot passion.

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#23
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Re: Surge Protective Device

02/03/2017 2:33 PM

Agreed. I hate the lyin' downs, they just sit and watch you and wait for the lyin' arounds to gather, then they swarm like doughnut holes to a jam jar. So that snarly beast with a snottery nose, es'chewed you up a tad that you are sizzlin' with the d'evil. Ah well, what can you do with these democrantics, they get up everyone's nose, and had a fair go at screwing things up world wide.

But if you want to stop a lyin', wake up. And BTW, definitely not Safrican.

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#25
In reply to #18

Re: Surge Protective Device

02/06/2017 5:48 AM

Surprise!!!!!

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#13

Re: Surge Protective Device

02/03/2017 4:53 AM

G/A to Lyn.... And pay attention to the installation recommendations made by Schneider. There has been a lot of development around Surge Protection and many of the "old school" electricians I have had in to work on our rather complex set-up have certainly not kept up to date. Here are some pointers worth looking into:

  1. Ensure that the connection to the main incoming Distribution Board is off the main buzz bars.
  2. The cables connection to the Surge Protector are heavy enough, at least 1,5 to 2 times the thickest connection coming off the buzz bars if the appliance does not specify a heavier cable.
  3. The connection cable is as short as possible but not longer than 300mm (12") and then directly to heavy earthing. The path of least resistance is where the surge will go.
  4. I have had great success in minimising surge damage by adding a high capacity surge arrestor to each bucket in the panel as well.
  5. Fit protection to each incoming end of auxiliary distribution boards. That helps reduce the number of reverse surges from your own equipment malfunctions and lightning strikes on your building/s.
  6. Check that you have correctly specified fault protection in the different d/b's to provide a good cascading protection level from the Electricity Supply Co's outgoing breaker to your incoming and all the way down to the last breaker...... get an electrical engineer to check your system. Too many electricians simply fit the first/cheapest kit they can lay their hands on. Respect to the crews that still do it the RIGHT way, you are few and far between.
  7. Make sure after installing energy saving equipment that the breaker capacity is also reduced to match the lower currents. Heavier circuit cables are not a problem unless they are starting to show signs of insulation degradation.
  8. Oh.... never let an accountant near electrical installation specification.
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#17
In reply to #13

Re: Surge Protective Device

02/03/2017 11:41 AM

Just recall Meneer, if you are on the highveld the surge from lightning is not the same as in Durbs. The BIL for Jo'burg is rated at 95kV and not 75Kv as at sea level. Barbeton and Benoni have the highest lightning strikes to ground.

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#14

Re: Surge Protective Device

02/03/2017 9:56 AM

What are your parameters? Oversized in what criteria? Voltage, Ka rating. On a OH line, in your house, in a factory, in a sub station?

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#15

Re: Surge Protective Device

02/03/2017 10:42 AM

Go Big at the panel and small at local equipment.

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#20

Re: Surge Protective Device

02/03/2017 1:05 PM

The most common mistake regarding surge protection is how it is installed. A simple demonstration at this facility will make a believer out of anyone.

Surge protection comes in a lot of forms. There are AC and DC types of surge protection. Usually most people are asking about the AC types. The common mistake is locating the protection on long leadwires away from the power source. Every foot of leadwire reduces the effectiveness by 500 volts of overvoltage. So, short leadwires are key to the protection. After that, since most surge protection devices burn up without letting you know, you are smart to error on oversizing. They have to be replaced eventually because they do die.

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