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Aredwood
3885 posts

Uber Geek


  #1996682 15-Apr-2018 23:35

mdav056:

I'm interested in this thread.  Many years ago, in London, I was working in a lab building equipment from ex-military 24vDC relays and steppers (back in the days when Tottenham Court Road was full of such stuff -- shows my age).  Arrived in one morning to a very nasty smell and found all my equipment blown, exploded, etc.  Very expensive, very depressing. The lab had a 3-phase 230vAC supply for some massive heaters, and the electrician told me that the neutral had blown and I would have been getting around 460vAC on the outlets.  I've always wondered if this was right, and why 460 vAC (a root-mean-square thing?).  Thanks for any technical person who can explain this for me.



When the neutral fails in a 3 phase system. You in effect get the equivalent of a series /parallel circuit involving the loads on each phase.

Imagine 2 of the phases have those big heaters connected to them. And your equipment was connected to the 3rd phase. When the neutral failed, you had your equipment connected in series with those heaters. And the phase to phase voltage across both. Since the heaters have a much lower resistance, most of the voltage would have appeared across your equipment.

Although normally your fault scenario would produce 400V instead of 460V.

And the above is why I said to the OP earlier to also unplug their appliances.





Jase2985
9956 posts

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  #1996694 16-Apr-2018 05:31
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why do you want them to respond? you have logged a fault, all you can really do is wait


 
 
 
 


mdav056
443 posts

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  #1996723 16-Apr-2018 08:01
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Aredwood:
mdav056:

 

I'm interested in this thread.  Many years ago, in London, I was working in a lab building equipment from ex-military 24vDC relays and steppers (back in the days when Tottenham Court Road was full of such stuff -- shows my age).  Arrived in one morning to a very nasty smell and found all my equipment blown, exploded, etc.  Very expensive, very depressing. The lab had a 3-phase 230vAC supply for some massive heaters, and the electrician told me that the neutral had blown and I would have been getting around 460vAC on the outlets.  I've always wondered if this was right, and why 460 vAC (a root-mean-square thing?).  Thanks for any technical person who can explain this for me.

 



When the neutral fails in a 3 phase system. You in effect get the equivalent of a series /parallel circuit involving the loads on each phase.

Imagine 2 of the phases have those big heaters connected to them. And your equipment was connected to the 3rd phase. When the neutral failed, you had your equipment connected in series with those heaters. And the phase to phase voltage across both. Since the heaters have a much lower resistance, most of the voltage would have appeared across your equipment.

Although normally your fault scenario would produce 400V instead of 460V.

And the above is why I said to the OP earlier to also unplug their appliances.

 

Thanks, @Aredwood, understand more now.  I probably had this stored as "about 2 x 230v", and I'll reset to 400 v now!





gml


Shin

274 posts

Ultimate Geek


  #1997272 16-Apr-2018 20:16
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@hio77 We have responed from Vector from facebook messenger, first ever contact from vector. they still not answering phones for an hour but the facebook messenger just works in an hour. they said we just have to wait. the irony is that our nextdoor is a local tennis club and they are using all the night light for their night games run while all the house down the road is completely dark. As a look of it on the pole and line we shares all same line, however they have power we are not. No its not a generator I already asked, they said they just have power as normal. Now I’m seeing more blue dots around my house, must be neighbors helped from their kids to use the app to lodge the fault, because they cant lodge fault by phone. Anyway I was bit unexpected that Vector giveaway UHT milk and canned food. And Flick is charging my electricity bill even they not getting metre reading and just assume consumption.

RunningMan
6108 posts

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  #1997283 16-Apr-2018 20:31
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Tennis club probably on a different phase to you


Shin

274 posts

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  #1997286 16-Apr-2018 20:36
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@RunningMan may be. i can see 3 lines on the pole, the house next to tennis club seems ok as well. my room is much brighter than before because of their night light and i can hear the bouncing tennis ball because my home is so quiet haha.

Shin

274 posts

Ultimate Geek


  #1997626 17-Apr-2018 10:20
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Just found blue dots are disappeared on my home and neighbors on outage map on Vector website. checked voltage again, nothing changed. still at 60v

 

Lodged fault again. The APP and website outage map is not functioning I guess.

 

Now it's more than 7 days since the blackout. We are not at remote area and there is no line down at tree as I drive through the road around.

 

 


 
 
 
 


MurrayM
1973 posts

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  #1997648 17-Apr-2018 10:39
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Didn't Vector admit that their app didn't work well and told people not to bother using it and that they'd review it after everything settles down?


Shin

274 posts

Ultimate Geek


  #1997654 17-Apr-2018 10:47
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Finally got the Vector person on the phone after 45min waiting.

 

They just said that even on low voltage just turn the main on and use whatever power you can.

 

 


Jase2985
9956 posts

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  #1997733 17-Apr-2018 12:19
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was it an actual technician or call center staff? if the later i wouldnt not be turning the mains on unless you were 100% in knowing where the fault was


hio77
'That VDSL Cat'
12554 posts

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  #1997740 17-Apr-2018 12:33
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Shin:

 

Finally got the Vector person on the phone after 45min waiting.

 

They just said that even on low voltage just turn the main on and use whatever power you can.

 

 

 

 

That's insanely bad advise!





#include <std_disclaimer>

 

Any comments made are personal opinion and do not reflect directly on the position my current or past employers may have.

 


cyril7
7761 posts

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  #1997782 17-Apr-2018 13:04
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Hi, if you were to understand why the voltage is sagging (ie its dropping across/between your house wiring and ground due to the probable loss of the return neutral circuit), then you should take that advise to reconnect with caution.

 

I realise that Vector staff are probably overwhelmed with work at this time, but this situation needs addressing immediately, its clearly not safe.

 

Cyril


Shin

274 posts

Ultimate Geek


  #1997826 17-Apr-2018 14:00
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Vector said it's feeder problem and many also affected. however they have no idea when it's going to be fixed. Advised to use power anyway, however voltage is now at 30v.


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