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Grizzly
19-11-2012, 07:46 PM
I seem to be having a run on Electrical problems.
The inside of this panel was rather warm, I shut everything down sharpish!


http://i851.photobucket.com/albums/ab77/grizzlysj/SAM_0488.jpg

Grizzly

monkey spanners
19-11-2012, 08:07 PM
Caught that just in time!

I wonder if the greening of the copper is due to chlorine from the pvc insulation on the cable degrading?

glenn1340
19-11-2012, 09:07 PM
A bit of black tape will sort that out, job done

Frikkie
08-12-2012, 09:29 AM
More than one of those connections is heat damaged. It could be poor crimping or wrongly sized lugs but maybe the wiring is undersized as well.

Grizzly
08-12-2012, 02:01 PM
Hi Frikkie.
Yours are sensible and logical comments as are most above.
However there is something strange happening on this site.
Yes the equipment at 15yrs is a little tired, but I have seen plenty of the same much older without these issues.
If you look at another photo of another cabinet on site, you will see that the Crimping is substantial.
The plastic Insulation around the cables does indeed appear to be degrading. In fact the reason I took this photo was because I had previously noted that the cables were "Sweating"?
My supervisor had even questioned my terminology used on my report sheet. So I wanted to use a photo to show what I was on about.

Sadly there was very little of the sweating I had witnessed the month before.
I am beginning to suspect the huge voltage fluctuations on site which we record with individual data loggers.
May have a part to play in this unusual cable degredation?
As I have said these panels are common, what is happening on this site however. Is not!
Grizzly

http://i851.photobucket.com/albums/ab77/grizzlysj/SAM_0528.jpg

r.bartlett
08-12-2012, 02:51 PM
perhaps the panel needs a heater?

install monkey
08-12-2012, 05:08 PM
http://www.rayleigh.co.uk/metapdfs/HRN-43-43N.pdf 3ph mains moniter, maybe get thermal imaging on the panel, will indicate hot joints

Frikkie
09-12-2012, 12:02 AM
I agree, the crimping looks like it was performed nicely with an indent crimper. From this picture as well I still have a suspicion of the lugs being oversized for the wire but it's difficult to tell from the photo plus the lugs don't look like they've overheated in this photo so maybe not.

I like the idea of thermal imaging, this is a great thing I'm sorry that we never had when I was working. It would be useful for predicting likely problems with terminations.

When you say that the wiring 'sweating', can you describe more what you mean by this please? Is there some kind of stick goo or glue type stuff coming from the insulation or is it more like water or damp condensation. I'm afraid am having difficulty finding the words to explain what I'm asking but maybe you can better describe for me please.

How large are the voltage swings seen on your data loggers? It's very unlikely voltage would cause cable or wires to deteriorate, it's much more likely to be load although the type of load that causes the most damage can't be seen with normal test meters.

Can your data loggers monitor reactive power and apparent power? Do you have figures you can post? Also has there been more problems with neutral faults than phase or line faults. Does the equipment have variable speed drives or adjustable speed controllers?

Sorry, I have lots of questions and not very many answers but the info will help.

I suspect you might have a problem with harmonics. Some of the things you say and also the age of the equipment point to this. There's different types of harmonics that can give entirely different problems. If the harmonics are in the Triplen range (3rd, 9th, 15th and 21st are the most guilty) this usually results in problems on the neutral because these are all zero sequence harmonics. Any triplen harmonics on any/all of the phases will add up to make a large single load on the neutral.

Another harmonic type which sounds more like your problem is the negative sequence harmonics such as the 5th, 8th and the 11th. These actually cause high iron losses, torsional oscillation and reverse torque in motors which results in the motor drawing a higher running current for the same absorbed shaft power. This might also cause burned or overheating lugs and wiring as well as tripping of thermal overloads and other protective devices. Harmonics in this ranges are often caused by variable speed drives and speed controllers.

I think you might need professional help if you have harmonic issues. You need special instruments to measure and define the problem and it's often a result of more than one cause. Existing power factor correction equipment could also be a contributer to your problems if it's causing resonance with the loads that are being supplied.

Edit.
The voltage fluctations might also be the result of series resonance caused by harmonics.

Magoo
22-12-2012, 01:28 AM
Hi Grizzly.
looking at both pics there does not seem to be a lot of crush taking place with hex crush crimp lugs and the one with punch crimp, may indicate crimp lug mismatch to cable conductor size, which would create a poor conductor connection and heating problem, the one with the punch crimp would indicated that it has been replaced before.

Grizzly
22-12-2012, 09:57 AM
Hi Magoo.
The both pictures are of leads that have been installed since new (15 yrs).
The second picture has obviously had the contactor replaced by me around 5 yrs ago.
I don't suspect the lugs.
However! I do feel that the composition of the cables PVC insulation together with the horrendous voltage fluctuations this site suffers with.
May well be a factor?

More lugs have their rubberised white sleeves fading and degrading.. Heat induced maybe?
Old age will have a bearing as well.
This equipment is near the end of its working life anyway. So its a case of "keeping it going"!
Thanks for the input though.
Grizzly

chemi-cool
22-12-2012, 12:50 PM
Grizzly, If you do a lot of checking out electrical connections, you must have a thermal camera with you.
In the second picture it is difficult to tell if the problem comes from the cable end or the contactor.
Even the cheapest one could tell you of the source of the problem.

Grizzly
22-12-2012, 02:35 PM
I totally agree, however our bean counters would never agree to the costs in the first place.
I out of habit always open panels and give the insides a once over.
It is surprising how often a quick visual can yield results.
Thanks for the input.
If you guys celebrate some form of public holiday ? Have a good break!
Grizzly

redroge
22-12-2012, 03:31 PM
I assume you,ve had the contactor to bits to check for pitted contacts?