**Show Us Your Installs!!!**

[wade88]

Was feeling quite creative when the cat died, so mounted some LED's in her eyes and fitted a photocell in the top of her head Just need another one now to make a matching pair.

It's what she would have wanted......

Wouldn't expect anything less from someone who has a cyanide and happiness avatar

 

[wade88]

Not being a facetious little ****...break free from where?

 

[Engineer54]

Not being a facetious little ****...break free from where?[/QUOTE

Tony has a valid point, ...Hes referring to pic #3, ...Plastic ties won't hold these cables in place on the occurrence of a heavy fault!! Cables carrying heavy fault current act like a fireman's hose under pressure, without a fireman or two holding it in place.

Generally, on panels where heavy cables are passing through a cable cabinet to a connection point a means of bracing those cables should be provided...

If you look at pic #2, you will see an example of bus bar bracing!! All panel bracing is designed to cope with the KA rating of the panel. If this is a 1MVA Gen-set, probably around 20 to 25KA

 

[Knobhead]

Not being a facetious little ****...break free from where?

Now E54 has added his bit. Can you now see why I'm concerned about it?

 

[wade88]

whats trefoil then?

- - - Updated - - -

 

[Engineer54]

whats trefoil then?

- - - Updated - - -

Correct!!! lol!!

 

[Silly Sausage]

Saw this today...
Should cleats be reclassified? | Professional Electrician & Installer

 

[t01474]

Good points made by everybody concerned. I'll bear them in mind for future works. Never even considered the tie wrap scenario
Would the same happen with 4-c SWA? Generally you see them just tie-wrapped to the ladder racking, tray, ect.

 

[Stroppy]

I had no idea cables jumped with fault current. Does the impulse come from the large magnetic field generated, or something else?

 

[Stroppy]

Wouldn't expect anything less from someone who has a cyanide and happiness avatar

Thanks, everyone agrees I'm an odd little man! Original cartoon: Cyanide & Happiness #2987 - Explosm.net

 

[pennywise]

I had no idea cables jumped with fault current. Does the impulse come from the large magnetic field generated, or something else?

This illustrates it quite nicely and why the correct type of cleats are needed.

Short Circuit Testing new - YouTube

 

[Stroppy]

Great video, most informative.

For non-mobile users: Short Circuit Testing new - YouTube

 

[Knobhead]

Good points made by everybody concerned. I'll bear them in mind for future works. Never even considered the tie wrap scenario
Would the same happen with 4-c SWA? Generally you see them just tie-wrapped to the ladder racking, tray, ect.

Under extreme fault conditions a SWA can be blown apart. But that would really be worse case scenario.
When singles are used then magnetic repulsion is a real danger. I’ve actually watched bus-bars bending under the start up load of a squirrel cage motor. That came about because a MCC panel had been extended several times without due consideration to the overall effect on the bars. “It’s only a 100HP motor, it’ll be OK.” The trouble was several “it’s only” situations that had happened over the years. To the point where the bars gave up the ghost, bent and shorted out.

 

[High Tower]

Tony and E54 thanks for that I must say I'm taking away some knowledge from this!

 

[Engineer54]

Under extreme fault conditions a SWA can be blown apart. But that would really be worse case scenario.
When singles are used then magnetic repulsion is a real danger. I’ve actually watched bus-bars bending under the start up load of a squirrel cage motor. That came about because a MCC panel had been extended several times without due consideration to the overall effect on the bars. “It’s only a 100HP motor, it’ll be OK.” The trouble was several “it’s only” situations that had happened over the years. To the point where the bars gave up the ghost, bent and shorted out.

I've only ever seen the results of a catastrophic fault on a dual supplied 3200A LV switchboard!! Where the bracing supplied by the manufacturer, was found to be, not up to the fault KA rating of the board. Which should have been 50KA but was in fact, barely reaching 32KA bracing levels. Two complete panel sections needed to be totally replaced and bracing upgraded throughout the entire switch board!! A very expensive exercise for the manufacture, which was only mitigated to a small degree by a wrong doing of the contractor who also ended up paying a pretty price!! lol!!

NOT one of my projects i should hasten to add!! lol!!

 

[Silly Sausage]

Looks like we're dealing with large forces here...

A three-phase short circuit in trefoil formation, the maximum force on the
conductor as detailed in IEC 61914:2009 (Appendix B Equation B.6), is
described by the following:

F[SUB]t[/SUB] = (0.17 x i[SUB]p[/SUB][SUP]2[/SUP])/S

Where
F[SUB]t[/SUB] = Maximum Force per unit length of cable (N/m)
i[SUB]p[/SUB]= Peak short circuit current (kA)
S = Centre-to-centre distance between neighboring conductors (m)

when the currents are in 100s of kA!!!



Interesting stuff!

 

[Knobhead]

Excel went in to E numbers :fuk2:

 

[Engineer54]

Looks like we're dealing with large forces here...

A three-phase short circuit in trefoil formation, the maximum force on the
conductor as detailed in IEC 61914:2009 (Appendix B Equation B.6), is
described by the following:

F[SUB]t[/SUB] = (0.17 x i[SUB]p[/SUB][SUP]2[/SUP])/S

Where
F[SUB]t[/SUB] = Maximum Force per unit length of cable (N/m)
i[SUB]p[/SUB]= Peak short circuit current (kA)
S = Centre-to-centre distance between neighboring conductors (m)

when the currents are in 100s of kA!!!



Interesting stuff!

Fault currents are limited by what the transformer in question can deliver into a fault!! Obviously the larger the Transformers KVA/MVA rating, the more current it can deliver into a fault!! For a typical 240/415V 1000KVA transformer, is roughly about 20KA...

 

[Silly Sausage]

Deleted, note to self, 'Don't attempt any maths after a few beers!'

 

[Knobhead]

So Ip is only 400,000,000 (20K²). That’s OK then :ack2:

It gets worse the more you look at it.

So if we allow 50mm conductor centers:

Ft = (0.17*(20K²))/20 = 3,400,000 N/m

A nylon strap’s going to hold that, isn’t it?

 

[Stroppy]

Is this force only generated between conductors carrying different phases, or does it happen in single phase cables too? I'm wondering if this effect happens in, say, your domestic T&E to a lesser extent with the lower fault current.

 

[johnboy6083]

To be honest in final circuits, the fault current is very low so although there will of course be repulsion, it will not be anywhere near the levels of the forces generated at the origins of larger industrial installations. Use Archie's formula to try the numbers for yourself. You could transpose it to see what fault current you would need to cause a certain force.

 

[Knobhead]

OK assume a fault current of 0.5KA on a 2.5 T+E, I get 127 N/m. It's not going to do it a lot of good.

To put this in to context under a load of 20A the 2.5MM T+E has got 0.2M/m of force acting within it.

 

[Silly Sausage]

OK assume a fault current of 0.5KA on a 2.5 T+E, I get 127 N/m. It's not going to do it a lot of good.

To put this in to context under a load of 20A the 2.5MM T+E has got 0.2M/m of force acting within it.

That would explain why cables blow themselves to pieces.
It's all starting to make sense now!

 

[Knobhead]

Have a look at Home - Scatco Europa Ltd. I installed quite a few of these. Look for the fault withstand current. It's not the CCC of the bus-bars, it's the current the bars will carry without distortion.

 

[Engineer54]

Have a look at Home - Scatco Europa Ltd. I installed quite a few of these. Look for the fault withstand current. It's not the CCC of the bus-bars, it's the current the bars will carry without distortion.

Along with the bracing to hold those bars in place during a high magnitude fault!! 50KA for 3 secs, takes a fair bit of bracing to be in place!! lol!!

 

[Knobhead]

The bars I watched bending were within 20m of the 1000KVA transformer. Don't know what current they were carrying at the time but couln't have been much above 1500A It was a 100HP DOL motor starting on an already loaded board. Normal running would be about 1100A The board was a Metro Vick open slate panel.

 

[Engineer54]

Never seen bars actually bending, a sight to see that i bet!! lol!!


I have seen package sub-stations (MV/LV) that have come from the factory with next to no bracing on the 3 phase bars entering the LV panel. That was after a factory visit (GE) too, ...where the units that were up for delivery to site were inspected and witness tested by myself!! Those 3 units were fine, but the next 4 units were crap, (12 X 1MVA units in all on that project) and after opening the first unit, instructed the contractor to send them back for remedial work, which both the contractor and myself will inspect at the factory, before they are shipped back to site!! That was in Saudi, but the factory was run and operated by GE (USA) at the time!!

 

[Knobhead]

The Metro Vic panel was from the late 40's, all open at the back. I was the wet behind the ears idiot that got talked in to watching what was happening.

After talking to Archy we’ve revised the figures for the 20KA calculation (I used A and not KA) the new value of F = 1360N/m. Not as bad as it was, but it’s going to throw things about violently if the cables get loose. The last transformer install I did I used 3.5T of cable on the secondary side. I wouldn’t fancy getting clobbered by that lot.
As Archy said the film of the multi-core cable exploding says it all.

 

[Silly Sausage]

You'll notice I've edited a few of my recent posts!!!

 

[Knobhead]

I'll sort mine out tomorrow. I'm knackered at this time in the morning!

PS it gets interesting if you convert it to Kg force

 

[Engineer54]

That would explain why cables blow themselves to pieces.
It's all starting to make sense now!

Many factors involved, depends on the cable size, (they also have a KA/s withhold rating too) length of cable etc. More chance on a short length of cable, say between TX and Main Switchboard, than on a long run (depending where the fault occurs), as the cable will act as resistance/impedance, limiting the fault current the transformer can deliver into the fault...

As i say too many factors involved that can/will influence each other, to pick-up on just one aspect and predict what will happen under a given fault condition.
Safe to say, any fault that involves the full fault current of a transformer, will always be catastrophic, ...and expensive!! lol!!

 

[onions1066]

Engineer 54 you are obviously very knowledgeable but I've never seen you post any pics of your work up, come on I think it's time to show us lol

 

[johnboy6083]

Engineer 54 you are obviously very knowledgeable but I've never seen you post any pics of your work up, come on I think it's time to show us lol

I can see some material requisitions, snagging sheets and emails coming our way lol

 

[onions1066]

I can see some material requisitions, snagging sheets and emails coming our way lol

Not sure what I will get but I'm pretty sure there won't be a plastic tie wrap in sight and I'm pretty sure he will be hugging and earth rod in one of the pics

 

[Engineer54]

Engineer 54 you are obviously very knowledgeable but I've never seen you post any pics of your work up, come on I think it's time to show us lol

Should have asked a couple of weeks ago. Not that i have much in the way of past project photo's anyway!! What i do have are on the PC, and it's too late getting that out of mothballs now, as i'm off flying back tomorrow!! So you'll have to wait till the summer now!! lol!!

 

[wade88]

here he is

 

[gonefishing]

Is this a commercial unit for lighting displays?

 

[Gage]

Rewire sorting this mess out. Will post drawings and other stuff gradually as I do them

 

[Gage]

Rough and missing terminal numbers, just rough copies before a proper computer drawing neat and standardised. Pretty basic circuit as you can see but I thought I'd share

This is just a control panel for a Plasma Nitrider. The complicated side of this machine is all in an Electronic Circuit (which I have the drawings for if anyone is interested) it's packed full of inverters and rectifiers. The more complicated stuff comes with the Arc Detection parameters. My company had a Romanian Physicist custom make it for us, he apparently works on the LHC now lol.

 

[Gage]

Just realised the power circuit is missing the contactors/stop start. Wasn't thinking straight LOL

 

[Knobhead]

You may find the missing bits on Google :seeya:

Sorry Kid.

Couldn't help myself.

 

[Gage]

You may find the missing bits on Google :seeya:

Sorry Kid.

Couldn't help myself.

Would've been rude not to! Haha

 

[Kamikaze]

I know some of you speed freaks would have done this in 40 minutes but it took me a couple of days.

 

[dan86]

I know some of you speed freaks would have done this in 40 minutes but it took me a couple of days.


View attachment 17721

nice work matey

 

[CSEE]

Looking Good there!! Have you ever considering installing Slotted Panel Trunking to inside of the DB instead of cable ties around the cabling?? I always do this and think it looks neat, and a lot easier if need to trace cables out at a later date.
Not a critisism just some of my knowledge and learnings from over time.
Regards Darren

 

[Knobhead]

I know some of you speed freaks would have done this in 40 minutes but it took me a couple of days.


View attachment 17721

Time well spent kid.

 

[DL electrician]

Anyone else used M2??

Anyone used any M2 Gear?

Apparently MK now refuse to stock any CEF's!!

 

[dan86]

I've used M2 stuff. customer recently supplied a few metal clad sockets to be fitted at their farm.

 

[Gage]

Rough and missing terminal numbers, just rough copies before a proper computer drawing neat and standardised. Pretty basic circuit as you can see but I thought I'd share

This is just a control panel for a Plasma Nitrider. The complicated side of this machine is all in an Electronic Circuit (which I have the drawings for if anyone is interested) it's packed full of inverters and rectifiers. The more complicated stuff comes with the Arc Detection parameters. My company had a Romanian Physicist custom make it for us, he apparently works on the LHC now lol.

Just a quick update, getting there, just doing bits and bobs when I can. Not as pretty as I'd like lol but getting rushed to do things, have to show progress while dealing with other breakdowns and what not. Also I duno what's happening with my photos lol