3 phase supply

[sparky 81]

Hey, I'm needing some advice. I'm at my wits end with this one. I have an underground supply (240 4core swa) feeding a 400 A breaker. The problem is every few days this panel keeps tripping out the breaker at the main distribution panel sometimes the generator supplying power. Could this be related to cold weather effects or the possibility of moisture getting in to the panel or cable??

 

[telectrix]

testing the cable and the installation it feeds might be a way forward.

 

[Knobhead]

Are you a qualified electrician? Because if you’re not call in someone that is before you hurt/kill yourself or someone else.

 

[Deleted member 26818]

Could be moisture due to condensation, as the equipment is very likely warmer than the environment.
Any moisture in the air within enclosures would very likely condense into liquid.
Or it could be a leak.

 

[Engineer54]

Could be moisture due to condensation, as the equipment is very likely warmer than the environment.
Any moisture in the air within enclosures would very likely condense into liquid.
Or it could be a leak.

Yep, and why small purpose made thermostatically controlled heaters are provided within decent switchboards and panels.

 

[Hawk81]

Quote removed


Tony's reply is not only helpful but the correct answer to give with the amount of detail you give in your op. how dare you join this forum and ask a question without giving any background details on your knowledge/experience then when questioned call someone those names. You will not find help here with that attitude. Either wind your neck on or jog on.

 

[Hawk81]

Quote removed

You can jog on too if you have nothing useful to say.

 

[telectrix]

joined in september, banned in december. :90:

 

[Engineer54]

Tony's reply is not only helpful but the correct answer to give with the amount of detail you give in your op. how dare you join this forum and ask a question without giving any background details on your knowledge/experience then when questioned call someone those names. You will not find help here with that attitude. Either wind your neck on or jog on.

I think he's a gonna already!! I don't think the Mod's are going to wear those sort of responses from a newbie!! lol!!

 

[LlandrilloSpark]

Sparky81- I think Tony's point is based on the fact that just lately the forum is becoming clogged up with DIYers & beginners doing things they shouldn't be, i have no idea if you fall into either category or not, but whilst we are all here to help fellow electricians (and apprentice's) we aren't here to guide non-sparks thru procedures they shouldn't be doing.
I hope I haven't offended anybody , but that's the facts

 

[sparky 81]

everything here is pointing to damaged cable in the ground was just wanting to get another perspective on it incase ive over looked something

 

[Engineer54]

You can find out if there is a sheath breech, by conducting a sheath test on the SWA cable!! You haven't mentioned any tests (and results) you have conducted so far on this suspect cable. So what tests have you conducted??

 

[sparky 81]

Sparky81- I think Tony's point is based on the fact that just lately the forum is becoming clogged up with DIYers & beginners doing things they shouldn't be, i have no idea if you fall into either category or not, but whilst we are all here to help fellow electricians (and apprentice's) we aren't here to guide non-sparks thru procedures they shouldn't be doing.
I hope I haven't offended anybody , but that's the facts

hey man ive been a spark since I Left school 15 years ago, I'm working with sparks who are older than me to, just thought it might be a good idea to through the question out there and see what kind of feed back i get.

 

[Knobhead]

The moment someone mentions a 400a MCCB repeatedly tripping I get worried.

With a 400A MCCB, if it was damp in an enclosure or on equipment there would be obvious blast damage. Similarly if the cable is damaged the fault will cause a drop in the insulation resistance which as Tel has pointed out you should test for. If this comes back clear I would start by checking the normal / abnormal running current of the equipment and the possibility of transient overloads.

The more information you can give the better the answer. Otherwise you’ll get the board’s speciality, wild guesses.

 

[High Tower]

We will not tolerate abuse or use of derogatory remarks aimed at any members.........Period!

 

[sparky 81]

The moment someone mentions a 400a MCCB repeatedly tripping I get worried.

With a 400A MCCB, if it was damp in an enclosure or on equipment there would be obvious blast damage. Similarly if the cable is damaged the fault will cause a drop in the insulation resistance which as Tel has pointed out you should test for. If this comes back clear I would start by checking the normal / abnormal running current of the equipment and the possibility of transient overloads.

The more information you can give the better the answer. Otherwise you’ll get the board’s speciality, wild guesses.

this is more like it.........there is no obvious blast damage........there is no access to the outer sheath of the cable, the cable is buried.........the previous installation was to NEC standards now converted to BS, meaning the yanks installed the main feeder cables using swa but never glanded to the panel as this not a requirement in the nec code.........Done an insulation resistance test and a continuity test........between L1 & L3 to earth the reading we're gettin is around 280 ohms........

 

[Knobhead]

Sorry to say this, looks like you've got some digging to do.

Back in a minute. Got a calculation kicking about somewhere that may help finding where to dig.

 

[Knobhead]

Can you fill in the values? They're going to have to be faily accurate.

 

[Engineer54]

this is more like it.........there is no obvious blast damage........there is no access to the outer sheath of the cable, the cable is buried.........the previous installation was to NEC standards now converted to BS, meaning the yanks installed the main feeder cables using swa but never glanded to the panel as this not a requirement in the nec code.........Done an insulation resistance test and a continuity test........between L1 & L3 to earth the reading we're gettin is around 280 ohms........

I think you'll find that glanding of SWA cables IS a requirement under NFPA 70 (NEC electrical codes) But like the UK, there is always a rouge element!! lol!!

You won't need a sheath test with IR readings like that. As Tony stated looks like you or someone else is in for some digging!!

 

[Engineer54]

Can you fill in the values? They're going to have to be faily accurate.

And that will only work if you accurately know the route taken by this cable!! Otherwise it's all down to your thumper and looking for the smoke!! lol!!