SPD protection commercial and industrial

[LastManOnline]

I would never suggest a SPD protects (in spite of the name) - Extension leads (with SPD) for example, talk about reducing the potential impact of surges.

Same with SPD, they reduce the possibility of damage due to a surge, not eliminate it.

This is a critical point really. In the the event of an overvoltage lasting more than a few seconds, standard SPD,s are utterly useless. Having recently experienced this scenario I will be henceforth stressing to all customers that they should enquire from their electrical appliance suppliers as to how vulnerable their products are to surges and what measures they recommend in order to protect them. The whole "risk assessment" scenario is a joke.

 

[pc1966]

The whole "risk assessment" scenario is a joke.

Sadly risk assessment for lightning based over-voltage is fairly easy (for the sort of crude level used in the regs) as lightning statistics are well researched and some empirical models of strike-to-overvoltage are know. You can even watch real-time maps of lightning activity on sites such as this:

Lightning & Thunderstorms - Europe

Blitzortung.org provides lightning and thunderstorm information in real-time on maps for USA, United Kingdom, Australia, new Zealand, Europa, Africa, Asia and other Countries.

www.blitzortung.org

What is all but impossible is to predict the occurrence of a DNO fault such as an open PEN, and as you say there is no SPD going that is going to deal with that. Best solution would be a nice deep long earth connector, say like a metal water pipe. Oh, we got rid of those?

 

[LastManOnline]

What is all but impossible is to predict the occurrence of a DNO fault such as an open PEN, and as you say there is no SPD going that is going to deal with that.

1) And that information needs to be passed on to the client. "Standard SPD, s give no protection against DNO faults".

2) The client should also be alerted to hold equipment suppliers to account regarding their recommendation for best type of SPD for their product. And ideally get them to supply it.

3)Client should be advised of the need for periodic monitoring of the installed SPD. (similar to an rcd.)



In fact in best case scenario, I see standard SPD, s primarily as a source of protection for electronics connected to fixed wiring (led lamps, sockets with pcb, s, fire detectors).

Best solution would be a nice deep long earth connector, say like a metal water pipe. Oh, we got rid of those?

If only.... ?

 

[i=p/u]

The electronic equipment couldn't afford to adopt this so they launched it this way, due to costs in procdction and very likely product size..

 

[IAmSparkytus!]

443.4 Overvoltage control
Protection against transient overvoltages shall be provided where the consequence caused by overvoltage could:
(i) result in serious inj ury to, or loss of, human life, or
(ii) result in interruption of public services and/or damage to cultural heritage, or
(iii) result in interruption ofcommercial or industrial activity, or

Apologies for my ignorance on this but interruption of commercial activity being what exactly? Damage to equipment preventing commercial premises from operating?

 

[pc1966]

Apologies for my ignorance on this but interruption of commercial activity being what exactly? Damage to equipment preventing commercial premises from operating?

Basically yes.

You can imagine how much money a business would lose if their tills, etc. all died after a local lightning hit and they had to wait a few days before they were replaced. Even more so for anything fancier.

 

[pc1966]

Its not just the lost revenue of course, as such a business might also be the only local pharmacy, etc, that folk really depend upon.

 

[LastManOnline]

You can imagine how much money a business would lose if their tills, etc. all died after a local lightning hit

How confident are you of standard SPD, s being able to cope with lighting strikes?. I can appreciate that transients caused by switching within the home or perhaps transients eminating from the DNO supply are easily dealt with by the SPD. But a lighting strike seems a much more aggressive proposition. Is there a particular SPD you would recommend for domestic installations?
And Regarding periodic testing of them?

 

[pc1966]

How confident are you of standard SPD, s being able to cope with lighting strikes?. I can appreciate that transients caused by switching within the home or perhaps transients eminating from the DNO supply are easily dealt with by the SPD. But a lighting strike seems a much more aggressive proposition. Is there a particular SPD you would recommend for domestic installations?
And Regarding periodic testing of them?

It all depends on how much energy the SPD has to handle. That really is the distinction between Type 1 that are rated for the 10/350us shape of a direct hit on the system, and the Type 2 that are rated for the 8/20us shape from induced surges from something nearby being hit. So for a given peak current the Type 1 has an order of magnitude higher energy rating (and higher price tag, of course) than Type 2.

Unless you are the tallest thing around (in which case you ought to have a LPS anyway and then the regs say SPD must be fitted and manufacturers say they must be Type 1), or at the end of a long overhead LV supply, then the Type 2 SPDs that go in to most "18th edition" CU should be fine as you are unlikely to see the sort of energy that a direct hit delivers.

The SPD can be tested with a normal IR tester, basically if they "fail" at 500V and pass at 250V then you are seeing the usual MOV characteristics. Though some Type 1 have GDT elements and only show up if you try the 1000V test (often you get a slight squealing sound as the IR tester keeps charging up its HV supply then the GDT fires discharging it and then clears, so the cycle starts again).

In situations where it matters they work, or if you live in an area with a lot of lightning activity, then checking the SPD is obviously important. When folk don't test their RCDs twice a year they could also be not checking the good/bad flags in their SPD...

While the cheaper (usually single module) SPD that come for "free" with the likes of the Fusebox CU lack it, the higher-end SPD often have the option of auxiliary change-over contacts that can be used to generate a warning that they have failed, so even multiple DB over a wide installation could be centrally monitored. If you had a hospital, data centre, high-end engineering workshop, etc, than I think though ought to be done, but I suspect it is rare!

Edited to add: The monitor contacts are mechanically actuated by the plug-in modules, so you can test the monitoring simply by pulling a module. Handy really, as it warns you that someone has pulled a module....

 

[pc1966]

In terms of choice of SPD then for most domestic Type 2 cases I would go with whatever the option is you get with your favourite CU.

If it was for something higher-value or where Type 1 performance is needed then I would probably go with one of the bigger European suppliers like Dehn, or a company that specialises in LPS stuff like Kingsmill Industries:

Surge Protection - Kingsmill Industries

Surge Protection Devices protect electronic equipment from the damages caused by the secondary effects of a lightning discharge,...

kingsmillindustries.com

I suspect that Dehn make SPD for a few companies as the Wylex replaceable-element SPD I have seen look suspiciously similar but a different colour of plastic...