Power surge and fire

[Engineer54]

Nick,

This is not just a phenomenon associated with PME, this could happen with any LV distributed supply system... It's only the neutral earth problem that comes with PME supplies...

It is as Tony has tried to explain, and his right, it is difficult to explain without being able to show the various stages of vector shift!!

 

[GLENNSPARK]

This is a bit over me (at the moment) but i will be asking all sorts about this at college this year.................

 

[nickblake]

Nick,

This is not just a phenomenon associated with PME, this could happen with any LV distributed supply system... It's only the neutral earth problem that comes with PME supplies...

It is as Tony has tried to explain, and his right, it is difficult to explain without being able to show the various stages of vector shift!!

Totally agree 54 didnt quite make it as clear as i could have dont think i was awake this morning

 

[nickblake]

Just a slight up date , All the damage caused , blown up lights till phones TV's etc shop owner has told me she has been told me that scottish power has stated that anything damage after there meters is not there resoncability so realy i think we should all inspect our insurance policies

 

[Knobhead]

This is what I meant about phase shift and voltage.

Blue is current.
Red is voltage.

Balanced

View attachment 7250

Unbalanced. A bit like me :iamwithstupid:

View attachment 7251

 

[nickblake]

Thats a cracking explanation , i look like the bottom one first thing in the moring , or trying to find my way back from the pub

 

[Knobhead]

Just don’t ask me to put power factor in it, I know the theory but with the 20 year old drawing package I’ve got I’d rather put my fingers in a food mincer!

It would defiantly look like me on the way home!

 

[nickblake]

I keep telling myself i must get my theroy books out again ,and refresh my knowlage ,its all in my tiny mind some where so easy to get lost in the complexity of electricity

 

[johnboy6083]

I was going to suggest that adding an earth rod with a 16mm min CSA to the MET would alleviate this, but I suppose that you would then get the streets neutral earthed at your rod! However if it became a requirement that every property had a rod in addition to a supplied earth, then maybe the risk would be reduced.

 

[Engineer54]

I was going to suggest that adding an earth rod with a 16mm min CSA to the MET would alleviate this, but I suppose that you would then get the streets neutral earthed at your rod! However if it became a requirement that every property had a rod in addition to a supplied earth, then maybe the risk would be reduced.

All or most council house estates built in the 50's had exactly that!! All were TN-S and all were provided with an earth electrode.

 

[johnboy6083]

Is it something in your opinion, that should become commonplace once again? I think so. At our companies offices/ warehouse we have a supplementary rod. As a minimum I think it would reduce the effects of a lost neutral.

 

[Knobhead]

It would be a good idea. My view is the more earths the better.

John have a look at http://www.electriciansforums.net/electrical-forum-general-electrical-forum/21227-tingley-taps.html for what happens with neutral - earth faults.

 

[Engineer54]

I would like to see such a system in place, but i think in these days of financial restraints and project costings, you have as about as much chance as seeing a pink pig with blue dots flying past. ....lol!!!

 

[johnboy6083]

I agree the more earths the better, especially in industrial environments. I do hate fitting bonding straps to tray, when you already use joiners, or links on trunking, again where you've used joining plates. I can't see the logic in them. Pointless. Only time I'll happily fit a bonding strap without being told too, is on a fresh air bend, or to bond between separate trays.

 

[nickblake]

Im suprised TNCS has not been banned and go Back to TNS it fun trying to get the screws out of a three phase metal clad CDU when there a neutral fault i pulled the main fuses still live ,ended up disconnecting the main earth , SP said it could be 3 hours before the attended i couldnt leave as it was so didnt have much choice