Worse case high voltage scenario

Status
Not open for further replies.
R

ronaldrc

Senior Member
Location
Tennessee
Had something on my mind that Bennie Palmer use to talk about.I believe this is what he was trying to get across to everyone and no one agreed with him click on the URL below and examine the picture closely please.The bond between the primary and secondary of the utility transformer can be very dangerous and we should maybe consider doing away with it.Unless Someone can explain how it benefits some how.

http://home.comcast.net/~ronaldrc/wsb/High_voltage_illistration.htm :)
 
Interesting scenario that's seldom spoken about. I havn't really ever taken any recordings that have ever evidenced anything approaching that, however. I notice that much of the distribution primary in many areas is a loop feed or double-ended (however they say it in your area), so a loose primary neutral would cause less of an issue.
 
mdshunk said:
Interesting scenario that's seldom spoken about. I havn't really ever taken any recordings that have ever evidenced anything approaching that, however. I notice that much of the distribution primary in many areas is a loop feed or double-ended (however they say it in your area), so a loose primary neutral would cause less of an issue.
Click to expand...



Mark

I have no idea of what you mean by the loop or double ended feed. I am not a lineman but I do know 4160 0r 7200 volts is a voltage you don't want to have traveling in your #12/2 nm romex, it might just arc a little bit, its hard too take voltage readings from a pile of ashes.

In the wosre case here you can not say there would not be high voltage on the premise wiring.
 
ronaldrc said:
I am not a lineman but I do know 4160 0r 7200 volts is a voltage you don't want to have traveling in your #12/2 nm romex,....
In the wosre case here you can not say there would not be high voltage on the premise wiring.
Click to expand...
That's true, but I was simply pointing out that there are schemes that exist within the infrastructure to prevent or lessen these occurrences. For it to occur, the service would have to be on a radial spur.
 
Pictorial example of simplified loop primary, not to be confused with a network primary:

loopprimary.jpg
 
Yeah, but you're talking about a huge shift in how things are done. A bit like fighting windmills. It practically takes an act of God to get the PoCo to install something as simple as a Ronk blocker. Lord only knows what it would take to get them to separate the pri and sec neutrals.
 
Last edited:
ronaldrc said:
Mark

You are right.

But if this is as a great danger as it looks like it might be.
Then the word needs to be put out. :)
Click to expand...
Good luck with that. Two bushing pots are probably 20 dollars more. ;)
 
But if this is as a great danger as it looks like it might be.
Click to expand...
Taking the bond out may even increase the danger. In the event of a primary to secondary winding short or a primary line that drops across a secondary line, without the primary to secondary grounded conductors bonded together, the only fault clearing path is the building service grounding electrodes.
Don
 
Don

I do not buy that.


Power utility Co. should not be able run high tension lines where they able to fall on a secondary feed or premise wiring.
Nor should a builder be able to build there.

I do know that in one of our neighboring cities where I wired a new nation wide Atuo parts store the owners of the property had to put the high voltage lines 3 ft. in the ground at his expense before they would issue him a Bldg. permit. Oh he furnish the materials and labor including the high voltage cable,Pvc conduit and the rigid galv. long sweep Ells.

And since I'm not a high voltage Electrician they did furnish the labor and men to make the connections on both ends.So considerate of them. :)
 
Last edited:
Ron,
I do not buy that.
Power utility Co. should not be able run high tension lines where they able to fall on a secondary feed or premise wiring.
Click to expand...
Take a look at any overhead system...the primary conductors are installed above the secondary conductors. Note I am not talking about high voltage transmission lines, but about the distribution lines which in many areas are 34.5kV. Even where the disrtibution is only 4.16kV the lack of a bond between the primary and secondary grounded conductors would limit the fault current and increase the time for the primary distribution system OCPD to clear the fault.
Don
 
ronaldrc said:
Had something on my mind that Bennie Palmer use to talk about.
Click to expand...
I'd like to be sure I understand what would happen in the scenario pictured, as the explanatory text is rather limited.

With "earth" as the 0V reference, in normal operation the primary conductors are at 4.16kV (ungrounded) and 0V (grounded). The center tapped transformer gives secondary voltages of 120V / 0V / -120V. If the grounded primary conductor develops a high resistance and all the earth connections are also of high resistance, then the primary grounded conductor could rise to, say, 2.00kV above ground. Then the center tapped transformer gives secondary voltages of roughly 2.06kV / 2kV / 1.94 kV above ground, with obviously bad results. This is because the bond between the primary and secondary grounded conductors insures they are the same voltage above ground.

Is this a correct explanation?

Thanks, Wayne
 
Yes Wayne

Thats right

Simply put if the primary grounded conductor opens upstream then the other route left open for the 4160 volts would be your house neutral and that would make a mess and just maybe and I do say maybe that happens more often than we want to believe.The resistance of the ground between that poles grd. rod to the next one through the earth would be very high.

Like I said earlier Its hard to trouble shoot a pile of ashes.

I know I am sounding like some of the our paranoid customers.
But thats the way I see it.
 
Utility grounding jumper Redrawn

Utility grounding jumper Redrawn

I have redrawn this scenario with the utility grounding jumper.


http://home.comcast.net/~ronaldrc/wsb/High_voltage_illistration.htm

Chances are of this ever happening are very slim.
But never the less it could happen.

And if you are one of the ones that say well anythings possible,
well theres the posiblity it could be your house.

There are other scenarios that could be just as dangerous.

Stuff does happen :D
 
Don

About the high lines you are right, but I want to point out this danger.

I am not sure which would be the worser of the two.

Seems like the utility never get any concern as far as most electricians are concerned.

If someone complains of a voltage surge the electrician always assumes it couldnt be any higher than the 240 volt secondary.

This is not hard to understand and I'm sure this causes surges all the time
and a lot higher than 240 volts. :)
 
Help with question

Help with question

Hello

I see a problem with a voltage feed back by bonding the primary and secondary grounded conductors on the final distribution Utility transformer
serving so called Separate Derived Systems.

Others also find problems with this by creating stray voltages on farms
I see that , but I think it could result in a far greater danger than they do.

The url below is a link to their report on it.

http://home.comcast.net/~ronaldrc/wsb/SV_Utility_.htm

I do have a question for the Utility Engineers on this forum.

I can not do the math and do not have the field experience in this area
to know the answer to the question I am going to ask.

The question is: Less assume that the ground between the pole the transformer is attached to and its ground rod are at the maximum allowed
resistance to the next ground.Would this maximum allowed resistance be low enough to pull the primary voltage down enough across the primary coil enough not to be dangerous? I do assume this resistance is considered? :)
 
This is the recurring nightmare of the multigrounded sytem neutral circuit arrangement used (as far as I know) exclusively in the US, and in particular the problems produced by the bond between the primary and secondary neutrals.

It's shortcomings are well known. On this very site you will find a copy of a document entitled The Hazardous Multigrounded Neutral Distribution System And Dangerous Stray Currents (PDF) - highly recommended reading.

It is known that this distribution arrangement contributes directly to the stray current problems, swimming pool and marina tingles, gradient steps across RV parks, agricultural problems (particularly with dairy cows) and multitudinous other issues.

And just recently I found This account of a lineman getting thrown off a pole due to a rogered multigrounded neutral system. Lucky lad, it could have been worse.

I doubt that this All American Beauty will be scrapped in any of our lifetimes, but it's good the issue continues to be aired.

As a postscript, the NEC is also hampered by the same blinkers, as it requires almost without exception that a transformer derived SDS (ie the "isolating" transformer secondary) has it's neutral bonded to the primary neutral, and although there are cases where this is sensible, this inflexible requirement removes the possibility of an isolating transformer as a safety device, as, well, basically, there is no siolation between the source neutral and the secondary neutral, and by extension, from the so-called isolated secondary and the MV distribution neutral conductor.
 
Only two additional issues I can think of:

1. Without the HV/LV neutral bonds, the utility would lose all of the millions of free grounds that need and use.

2. No HV/LV bond would require surge suppressors an every xfm.

Those two changes would really bug the utilities. Can you ever imagine a utility saying they were wrong and this HV/LV bond was not good for the customer. Hell would freeze over first. :roll:

carl
 
Several months ago,in an earlier thread,I discussed people within a community swimming pool receiving electrical shocks when they attempted to leave the pool.The pool was within 100 feet of the main electrical transformer feeding this town(the pool was inadvertently providing the ground for this substation).The solution was to remove the neutral jumper between primary and secondary of the pool's distribution transformer.This was approved by all the electrical safety agencies.

Result:

There were no electrical shocks reported anymore by the swimmers
 
Status
Not open for further replies.
Top