Rubber Flex Insulation Resistance Failure
Вставка
- Опубліковано 28 сер 2019
- A short piece of flex which shows unusual behaviour when tested at 500 volts. Also includes a demonstration of cable capacitance when testing insulation resistance.
► Support this channel:
Patreon: / jwflame
PayPal Donations: xo4.uk/?PPP
► Social Media:
Twitter: / jwflame
Facebook: / jwflame
Instagram: / jwflame
► Contact info, sending stuff in: etc.:
xo4.uk/?YTT
► Website - More on this video and many other subjects
Website: www.flameport.com - Наука та технологія
Some natural and man made rubber cables over time in damp or wet conditions go hygroscopic and actually absorb moisture. Then you get exactly the effect you got with the Megger. The insulation “breaks down” the longer a standing voltage is left across it.
Not far off the 100k subscribers now john!!
well deserved youve given free quality informative videos to help so many of us and for that im very grateful keep up the good work sir 👏
I echo that mate, a very informative selection of video's to help anyone interested in electrics :)
John , When i worked at a local electrical wholesalers 15 years ago, we had a batch of Collingwood spike lights ,where the paralleled leakage from the porous cable caused the rcd to keep tripping ,the customer brought them all back , and i offered to replace all the cables with some quality British rubber cable, problem solved, But probably invalidated their warranty
Great to see a real world example. Thanks John.
Very interesting video as always thanks!
I had exactly the same thing on a garden lighting call out last week, I ended up stripping the flex down to visibly see what was wrong,I even think it was the same make of cable,poorly made cable= moisture ingress I presumed
Oh what a fun job we have! Thanks John. Never take anything for granted eh? I found some conductive silicon sleeve recently.
Silicon is generally semi-conductive.
He means *silicone* .
Interesting video thanks mr ward. I’ve come across some 6242Y cables that have a much higher r1 r2 and r n than should be.
I used T&E 4core few months ago doing emergency lighting and exactly same things happened and according to NiC there’s over 20m meters of faulty cables come to uk from Turkey and there are still in many wholesalers to be discovered
PVC insulation often contains some (normally VERY small) quantity of lead. PVC insulation from China often has considerably more lead than normal. Lead is, of course, conductive, and combine that with moisture leaching through it, the minerals in the water may be reacting with the lead and forming conductive lead salts, which create numerous tiny current paths. I'd get a cheap lead test kit from a hardware store or similar, and rub the swab from it all over the insulation off those wires to see if there's lead in there.
But this is a rubber cable; I didn't think those used lead?
@@longrunner258 Rubber cable is usually vulcanized by extruding molten lead over the sheath before being autoclaved to finish vulcanization. This lead is then cut off and reused.
Great video JW.. I find this often with T&E connected to outside light fittings (which obviously is not permitted unless contained) the UV light breaks down the pvc insulation, cracks and moisture gets in. IR fails or is well below 2 megohms. I suspect that cable is not to spec or a Chinese fake cable 🤔 would be interesting to see what curren/voltage it could take before failure of the insulation? You could pinpoint the weakness in the conductors insulation then.
So I’m in a couple UK electrical groups on Facebook and observe all kinds of things that are very different than here in the states.
Here in the states there is a stamp on pretty much every cable from what certifying lab has accepted that cable, like UL, etc. also most of our cables here also show voltage rated for.
The other thing that blows me away about the UK and apparently Australia also and probably many other countries that I don’t know. The fact that you do all these tests on your installations. We do nothing like that here in the states. Nobody carries a meter like everybody I watch in the UK. We don’t do an Any kind of certification when we install stuff and we have nothing on any kind of regular basis. If it screws up your call us so we come out and find it.
If you do a new install that needs a permit from the city or county or whoever, all they’re really looking for Is how you installed it. Usually it’s two inspections. A rough inspection for your cabling and conduit, and then a final inspection after the walls and finish are done.
Cable in the UK generally does have makings from an aproval body (though I'm not sure it's mandatory), most commonly either BASEC for UK-specific cable types or ◁VDE▷ for harmonized flex. As far as voltage rating for harmonized flexes like the one in this video that is covered by the harmonized cable type code. The "05" in H05RR-F means that the cable is rated 300/500V (the first voltage being relative to ground, the second being voltage between conductors). T&E seems to have the voltage rating printed on it.
Normally though voltage ratings aren't something we worry about because we don't have a proliferation of voltages.
If you are interested in the rest of the cable code, the "H" tells you it's a harmonized cable, the first R tells you it's rubber insulated while the second R tells you it's rubber sheathed and the -F
tell you it's a flexible cable.
I'm surprised that such a class of cable is allowed in such an installation.
If armoured cable is too much of a pain and mains power is needed for garden lighting then what is done down here is to use 12V lights. For larger installations I think 24V or 32V is used. This way anyone can install the lights and an oops with a mower or other implement isn't a major issue.
i once worked to seal up the discharge of shower sump pump while it was running, not bad but quiet noticable tingel in the water
I need to see John play that keyboard!
That's not any old keyboard.... it's a Hammond M-102 organ, as used by Rick Wright on all of the Pink Floyd's albums. You can see him playing one in the performance film "Love at Pompeii". I somewhat regret having to shed mine a few years back.
@@Peter_S_ and of course famously used on A Whiter Shade of Pale. I wonder if JW can play that particular piece :)
@@jaycee1980 I think if you own an M-100 series Hammond it's rather mandatory. I used to have the exact same M-102 and Whiter Shade of Pale was one of the first things I played on it.... right after Smoke on the Water which just didn't sound right until I patched a guitar distortion pedal into the circuit.
I hope he just surprises everyone one day and does a "Phantom of the Opera" style video. 😂
Hi John,
Can you test the inner resistance of that black outer shell?
The wires were inside, not on the outside.
I'm interested to see if degraded rubber caused some of the issue.
Thanks
Larry
some years ago it was found the rubber scan coil 'wedges' in some crt tvs became conductive and even 'leaked' out corrosive 'goo' onto the scan coil windings which turned them green with corrosion ., i've seen this for myself !
@JW: Do you have a Leslie connected to that M-102?
Hi John. I'm intrigued how the flex would have behaved in a 250v test, closer to actual operating conditions. I'm not denying that it would probably still fail, but would have been interesting to see.
Do you have any tips for outlet setup for using a welder at home? I have heard all kinds of things, such as that the cable inside the wall will heat up!
It would have been interesting to apply pressure to the cable while twisted or in the sheath and see what happened to the resistance/leakage? There may be one particular point where the leakage is affected more - or indeed over its full length.
Are you having your globe light on at the beginning and off at the end on purpose ?
Hello John, hope you are well. I've been looking into a techinque or equipment that would allow us to find an insulation damage on a buried conductor. We have voltage on the end but when drawing power it drops to 0 and the insulation resistance to earth is 0, so we believe it's partially broken, because we receive voltage but when current flows it drops so there must be a few wires still good but others cut. Any thoughts? It's a 1000 m run by the way.
You mention that some of the wires tested ok. I wonder if they had water in the junction boxes. Maybe the inner insulation is not water resistant and relies on the water resistance of the outer sheath.
JW can you do a video on how to calculate how far along the cable drum the fault is?
We’ve had a few odd faults where moulded on plugs have had insulation breakdowns, they have been all the same ‘Deka’ brand. Seeing that drum of flex rolled up, was wondering if you could do a video explaining why an extension cable shouldn’t be used rolled up?
He already did a video about high current through a coiled cable.
You could also try putting those wires into the oven for 30min or more at the cable´s max temperature rating.
Just to see if some moisture does indeed leave it or wheather the insulation is just degraded in some other way.
That's what I was going to suggest. May require longer than 30 mins however. Overnight at 80C might be good.
Expandable rubber sleeves also, I heard in the past
Yay recycling dirty milk bottles and posting them back.. You could have done the same test you did on the exterior insulation on the inner stuff after removing the copper.
It's been lovely weather for the neighbors to have a BBQ ,time to take the heather and big transformer into the garden with the other half of that cable.
If one end of this flex terminates inside a the spot light fittings that gets hot and the other end terminated inside a flooded with water junction box then the cable is turned into a 1metre long drinking straw.
Again, water being drawn up inside the cable should not prevent good insulation from doing its job. This low grade insulation is clearly water permeable.
I wonder if some ionic salts have migrated into the insulation material from the soil? Maybe actually an electrolytic reaction occurring when a voltage is applied.
Does a Megger test with DC or AC at 500 or 1000v and what current can it source? Surprised the ‘good’ cable showed such a long charge up time. Capacitance at maybe 1nF per mètre so should charge almost instantly unless the current put out by the Megger is at the micro-amp level.
meggers of this style put out a very small DC current
Nothing whatsoever to do with capacitance, the megger is measuring leakage current that is simply increasing the longer that a voltage is applied.
Could have taken one core and done IR test on the insulation of it.
Good example of Chinese gutta percha. Or crap rubber.
Thanks for sharing.
@Indosarnia Ningbo Huashun is Chinese, so you are wrong again. Why are you trying to defend sub-standard Chinese crap?
Why does the Megger warn when using 1000 volt test? Is it only because it sounds fancy? Can it upset you it you get that voltage between your hands and you can drop something? I couldn’t find the current used in the leakage measurement but it must be quite small.
How does Britain handle certification of components? I was expecting to see some sort of testing lab logo on that cable: UL, CSA, ETL, or whatever.
Paul Ste. Marie Exactly call, I was thinking the same thing. Pretty much every piece of cable you buy here in the states has the voltage ratings on it.
H05 stands for a "harmonised" 500V cable, RN-F is for the insulatoon type.
@@ponderstibbons3718 Yes, but who did the testing? In the US, I'd expect to see the testing agency logo and a listing/recognition number, e.g. "UL E123456". You can look up listing numbers on UL's website to verify authenticity and the specifics of the listing (or recognition).
Usually has BS(British Standards) number on it but this means nothing as the Chinese will make any old cable and print the BS number on it.
It seems to be a cultural thing in China where if they can cut corners they do.
@@123tinhat123 should be tested, check to British standard in order to be imported into this country.
Better still UK should manufacturer own cables, switch, socket so on. 😳
What happened to old wire colours code .which red as hot line and black as neutral
In North America, we use black for hot and white for neutral. Where there is more than one hot wire, they are black and red with a white neutral. Three phase is black red and blue for hot.
@@heronimousbrapson863
Yes .. that in north america but we are use in our country red and blue and yellow for three phase and black for neutral .
Apparently the UK changed officially to the blue/brown colour code in 2004. Not sure about the rest of Europe.
@@Cadwaladr
The rest of europe use brown and gray and black for hot line and blue for neutral .
Correct colours (not colors) for Australia.
It would be interesting to cut 15cm from both ends of the cable and test again. This way we could see if the insulation is deteriorated only on the parts that were not fully enclosed inside the black outer isolation.
Can you please explain why electricians in UK tie Line and Neutral together for insulation resistance test? Thanks.
That is done where equipment is connected to the circuit, and it's not practical to disconnect all of it.
@@jwflame Thank you John. I think I am missing something here. So, what happens when equipment connected to the circuit contains sensitive electronic components? The high voltage applied to the tied line and neutral conductor will NOT damage the electronics? Thank you for clarifying that.
What brand is the tester?
So if the readings on the machine is low it means there is a breakdown of the insulation. The higher the reading the better the insulation?
Yes.
@@jwflame Would i ever obtain a O.L reading on the device when carrying out these tests. If i did would it mean that my insulation is close to ''PERFECT'' insulation?
I have some generic power cords that look like this junk.
The insulation on the wires is very soft. It's so soft you can cut it with your fingernails.
I don't know what type of plastic this is but it's dangerous.
It also burns very well.
I have come across that soft flex too. As standard on AEG angle grinders. Soft flex on an appliance to be used around metal....
@@johnsimpson8263 I got curious and took my import angle grinder apart and it also has this junk wire in it.
I'm surprised there isn't more house fires from this trash insulation.
I'm also curious if this deteriorates like the butaline based junk on appliances that gets sticky?
I installed about 10 of GU10 spike lights with the same flex. Can't remember the make but bought them from TLC Electrical. Got called back about 3 times with the RCD tripping thought it was to do with damp getting in the fitting but eventually narrowed it down to the flex. Had them 13 months so manufacturer wouldn't take responsibility.This flex should not be allowed. Wasted my time and money.
The key to the issue was on the outer sheath. Its Chinesium.
We don't know that - damp may have got in at the ends.
@@millomweb Explain how damp getting in the ends would cause a good, non water permeable insulation to breakdown please.
DJ_PailTUK Correct, this is low grade Chinese crap. Weird how quite a few people in the comments are trying to suggest it's somehow not the fault of the cable.
@@ferrumignis I never said it would but it could create an electrical path around it.
@@millomweb How can moisture create a conductive path from one core, through two layers of insulation and into a second core unless the insulation itself has been compromised?
Would be interesting to slow heat those wires to drive out any moisture and test again.
They'd need to be heated in a dry atmosphere to drive the moisture out of the porous plastic.
Bake at 105°C for two hours, turning once every fifteen minutes.
Ensure product is piping hot before serving.
Maybe it's not water conduction but chemically altered insulation. Remember iron conducts but rust doesn't - so perhaps corroded insulators start conducting ?????
@@robroysyd Alternatively, put them in an air tight container with a desiccant.
Made by good old Ningbo Huashun, what could go wrong?!
Next time, spec Won Hung Lo Cable and Fireworks Corporation Ltd.
Have we discovered a new type of semiconductor?
No - we've known water as a semiconductor for years.
If you mean the fact that the resistance decreases as the voltage increases, that is called _negative (dynamic) resistance._ That´s not characteristic of a semiconductor though.
was the cable copper coated aluminum?
The way it twisted together easily makes me think it was actual copper.
@@Cadwaladr - I've seen copper plated steel stranded wire from China. That stuff is impossible to work with.
@@deadfreightwest5956 That does sound like it would be awful.
another example of fine chinese quality manufacturing!!
@Indosarnia And you know who installed those... how?
@Indosarnia You have a real bee in your bonnet about people calling out shitty sub standard cable don't you? Do you manufacture this crap?
Same thing actually happened to my original figure of 8 Xbox power cord.
Can you tell us the cord manufacturer?
Shouldn't really have that sort of thing left outside in the garden. But then again why do you need an Xbox in the first place.
@@longrunner258 No idea sorry it got thrown out.
@@g7mks383 It had been in the loft for a number of years, and I went on a clear out spree and randomly decided to test all the mains cords so I could get rid of the dodgy ones.
@@g7mks383 What a strange thing to ask 'why do you need an xbox'? Why do you need a phone or a computer?
This cable will self destruct in thirteen months.
Smeg !
Next, we shall test the lead and organic toxics content of this piece of Chinesium.
If you have no resistance in your flexing. . .
Try yoga
@Indosarnia dont worry. . It's just a PHASE. . . . Even if it is a reVOLTing thought
Thanks for showing us another reason not to buy Chinese rubbish. Well explained and proven with your trusty Megger. (It takes no prisoners)
Thanks John
Wow now im now better of test and how to do it far better
Im so proud of my mentor
Thanks now my mind is test eyes open
Your videos is my go back when im stackt
Then i go check fast tru your videos and found my answer
Thanks
I no people will said what a idiot better a idiot as im set up a fire
Then i said if anny one how not makes misstacks wow you a creat
That this people where i found plentty fualts misstacks
According to BS7671 it was within minimum required
That minimum in BS7671 is intended for an entire installation with multiple circuits, not a single piece of cable.
@@jwflame it’s also intended for one circuit for example: single socket installed in hall cupboard, total length of cable:20cm. Still the same rule applies. Bottom line is if you tested even whole installation with such a cables and you achieved more than 1MOhms you are not allowed to fail it . Nevertheless I agree there is something wrong with insulation of this flex . In order to find out we need to know BS of the cable and check testing procedure to achieve this British Standard
Faulty flex but okay
Could elaborate why the earth is a globe?
Absolutely no point - people have made their own determinations in that regard.
For the same reason that all the other planets are globes; gravity.
Made in China!
Testers faulty 😛