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Topic Title: CE Marking & Short circuit test
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Created On: 25 April 2014 06:40 PM
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 25 April 2014 06:40 PM
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AdrianWint

Posts: 261
Joined: 25 May 2006

I'm currently having a somewhat heated discussion with some work colleagues about the requirements of clause 4.4.2.8 of EN61010-1 of the CE marking standard.

For those that don't have access to this it basically states that its required to place a deliberate short circuit across any output from a piece of equipment & see what happens. This applies to 'utility outlets' which pass on mains power to a third party piece of kit.

The device in question has an IEC outlet. So, my colleague intends to create a shorting IEC plug which contains a hard link L-N, insert this into the IEC outlet & power up using the normal 13A bench supply ..... and see what happens (the outlet is protected internally by a B4A MCB so it should operate.... quickly).

I'm saying....wow... stop & consider. One doesn't normally deliberately place a short circuit across the mains! In fact we go out of our way (in testing dead) to make sure we don't do this. We need to consider the PSC at the socket outlet in question and try to understand and mitigate the risks here. What about the switch we use to close onto this fault, is it upto the job etc, will it fail? Should we do doing this from a normal 13A socket?

What is the collective opinion here? I am being over-cautious? Or is this OK and, as OMS would say, should we just crack on & get it done?

Comments please......
 25 April 2014 07:00 PM
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GeoffBlackwell

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Unless you are conducting the tests in a high fault level zone - such as the factory main switch room , the PSC is unlikely to be too great at a socket outlet.

However, your comments about using the switch on the 13A outlet are valid as I doubt that it is guaranteed to be capable of making onto a fault - certainly not repeatedly.

I don't have the latest copy of the standard but the one I have read makes no reference to test supply fault level.

Regards

Geoff Blackwell
 25 April 2014 07:20 PM
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OMS

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No test fault level is stated as far as I know - so you need to pick a suitable source that exhibits relativly low fault level and provide a switching device that can close (repeatedly) into the fault - say a 15kA MCCB set for non auto to act as the switch before any socket outlet

Plugging in at the bench socket seems a tad cavalier to me

Regards

OMS

-------------------------
Failure is always an option
 25 April 2014 07:22 PM
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Thripster

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What about anti-social EMI unless conducted in a protective environment?

Regards
 27 April 2014 08:27 AM
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AdrianWint

Posts: 261
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Thanks for the comments, Gents.

The point about the fault level not being specified is interesting. I hadn't picked up on that. Off to the deepest darkest corner of the factory I go......

I was initially thinking along the lines of using one of the 63A TPN supplies in the Engine Test bays and using a hefty contactor to close onto the rig in question..... but, of course, this will increase the fault current available.

I'm still not certain that I want to agree to a standard 13A socket being used as the supply, so perhaps we need to think in terms of a dedicated radial taken from a well chosen distribution board, terminated in something like a BS4343....

Adrian
 27 April 2014 08:29 AM
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AdrianWint

Posts: 261
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Originally posted by: Thripster

What about anti-social EMI unless conducted in a protective environment?

Regards



Indeed. And that is another can of worms, but, fortunately, outside of my remit :-)
 27 April 2014 04:54 PM
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cblackha

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I wouldn't expect any EMI issues with just doing a s/c test - it's a very transient event anyway.

I haven't had to do this particular test, but I'd be inclined to use an MCB, or other, perhaps double pole contactor designed to handle repeated s/c current

The manufacturer should specify overcurrent protection devices to be used with the equipment as per 6.11.3.1 or 9.6.2.
Any equipment fuses should be ceramic with minimum breaking capacity of 1500A (and not glass fuses)

Charlie
 30 April 2014 01:29 AM
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mapj1

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Oh sausages, now should I worry I wonder, I've a horrible feeling there is at least one piece of CE marked kit out there in the wild where we did no more than the 25A PAT test style overload. I may even have signed something about it being fit for purpose. Hmmm- oops ;-)

Be aware that the 'short circuit' current may be disappointingly (!) low depending on the length of the mains lead and what else like surgegard devices may be in between inside the equipment you are designing - the main effect is to briefly stress the N-E insulation by pulling N up to the midpoint of L and N. But if you are CE marking you will be robust against L-N reversal anyway won't you - that breaker is it double pole ? ;-)

Personally if I had to test under full stress, I'd power up the kit (not from any circuit that powers the company IT system or anything important like the coffee machine) and once its all done with inrush, then introduce the short circuit fault on the IEC lead, probably with a motor start style contactor from a bench supply some way away rather than my best mate's wire cutters or favourite screwdriver ;-)
I'd also suggest a pre-test with a known higher impedance in series (pile of 25m extension leads anyone?) to shake out silly vulnerabilities with less risk of serious damage.
Joking aside, please take great care.
regards M.

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regards Mike
 30 April 2014 09:48 AM
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OMS

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LoL - that'll be one of those "China Export" type CE marks then, Mike

OMS

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Failure is always an option
 30 April 2014 11:10 AM
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mapj1

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I think it may well have marks to show it as being to the standards required for 'fabricated cheaply in china' too.
Actually, in a fit of butterfies in stomach this morning I've just had a little play, and while testing is far from what would be accepted for type approval standard, based on a lab sample of one and abusing a starter solenoid I had from something else, it does indeed survive perfectly well with barely a flicker while a 13A fuse and a 16A c-type race to pop their dutch footwear (tested using both mains plugs for use here and in the wider EU ) so I feel reassured but I must admit it didn't feel very nice for a moment.
Lucky there are so few other non-compliant items out there is it not - ha.
regards M.

-------------------------
regards Mike
 30 April 2014 11:28 AM
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OMS

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All good then - lets hope you've still got a supply to the coffee machine and it's happy days

Regards

OMS

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Failure is always an option
 30 April 2014 12:00 PM
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mapj1

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Indeed.
Actually I strongly suspect that if the coffee machine supply round here ever failed in any seriously irreperable way there might well be exposed cables or even singles of some utterly inappropriate cross-section trailing off down the corridor towards the nearest live fitting, dis-board or sub-station or even out the window to a genset in the car park if required . Probably installed and energised faster than one could find the reg that permits the use of a 'protection ommited' strategy for certain types of critical safety of life supplies, which obviously that would be, or indeed could possibly raise the paperwork for any normal installation.

regards,
M.

-------------------------
regards Mike
 30 April 2014 01:05 PM
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OMS

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I did a job a few years back for a facility that managed major hazards.

At one of the early design team meetings we were outlining our approach to multiple normal, short break and no break power supplies all arranged with complete parallel redundancy and meeting design basis criteria that extended from a 1 in 10,000 year seismic event to a 1200kg mass being thrown at the building (basically a small car being picked up by a tornado) and everything in between including extreme hot and cold conditions and ballistic insult.

The very first response was that the tea point and coffee maker would be fine then, provided we could keep them fixed down and the water supply held up - and they weren't joking, even down to quantifying the bottled water inventory so they could use that for a brew if required.

Sensible chaps !!

Regards

OMS

-------------------------
Failure is always an option
 30 April 2014 01:41 PM
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James Broughton

Posts: 25
Joined: 25 May 2006

Quite right too!

Nothing like a good old cup of char whilst the world is collapsing around your ears.

I know a similar site where the whole area is being re-arranged, with the one constant being the positions of the kettle and water bottles!

-------------------------
'This place would be a paradise tomorrow, if every department had a supervisor with a sub-machine gun'
 07 July 2014 10:56 PM
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civi

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Joined: 26 May 2014

@AdrianWint: Hi, It is never safe to conduct this test as we can't put a short circuit to the mains without testing it and for me it seems crazy test whether is a normal 13A socket.

Edited: 18 July 2014 at 04:34 PM by civi
 08 July 2014 07:42 AM
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Zoomup

Posts: 157
Joined: 20 February 2014

Originally posted by: AdrianWint

I'm currently having a somewhat heated discussion with some work colleagues about the requirements of clause 4.4.2.8 of EN61010-1 of the CE marking standard.



For those that don't have access to this it basically states that its required to place a deliberate short circuit across any output from a piece of equipment & see what happens. This applies to 'utility outlets' which pass on mains power to a third party piece of kit.



The device in question has an IEC outlet. So, my colleague intends to create a shorting IEC plug which contains a hard link L-N, insert this into the IEC outlet & power up using the normal 13A bench supply ..... and see what happens (the outlet is protected internally by a B4A MCB so it should operate.... quickly).



I'm saying....wow... stop & consider. One doesn't normally deliberately place a short circuit across the mains! In fact we go out of our way (in testing dead) to make sure we don't do this. We need to consider the PSC at the socket outlet in question and try to understand and mitigate the risks here. What about the switch we use to close onto this fault, is it upto the job etc, will it fail? Should we do doing this from a normal 13A socket?



What is the collective opinion here? I am being over-cautious? Or is this OK and, as OMS would say, should we just crack on & get it done?



Comments please......




Hello Adrian Wint,
I'd be inclined to undertake this test situating the equipment behind a bomb-proof window, behind sand bags, using a robot to go into the danger area to operate the self destruct button whilst I wear my PPE earthed metal colander on my head. Good luck.

Bye,

Z.
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