What could cause a drastic variation in voltage on a municipal supply to a house?
Is it possible that something on the house circuit side of thee main switch is causing it? Or can it only be something on the supply side?

 

What could cause a drastic variation in voltage on a municipal supply to a house?

The described difficulty may owe to any of several conditions - prominent among them being:

1) Defective watt-hour meter/socket contacts.
2) Problems with the primary fuse, distribution transformer proper, or service drop line (similar considerations apply to secondary network systems).
3) Feeder or system-wide 'brown-out' conditions.

The good news is that all of the above are the 'POCO's responsibility -- Though it may behoove you to identify the fault prior to reporting difficulty (inasmuch as most utilities bill for 'unfounded' service calls...)

Is it possible that something on the house circuit side of thee main switch is causing it?

Assuming proper load-center OCP installation and absence of conspicuous arcing at or inbound of said load center - No!

Best regards and good luck!
HP

 

Addendum:

Re: 120V--N--120V service - an open neutral may produce the described symptoms Re: the 120V circuits --- Said circuits being thence 'stacked' in a 'series-parallel' arrangement line to line - permitting an EMF range at any 120V receptacle of (essentially) 0V-240V (dependent upon load distribution)...

Best regards
HP

 

Addendum:

Re: 120V--N--120V service - an open neutral may produce the described symptoms Re: the 120V circuits --- Said circuits being thence 'stacked' in a 'series-parallel' arrangement line to line - permitting an EMF range at any 120V receptacle of (essentially) 0V-240V (dependent upon load distribution)...

Best regards
HP

Tnx!
Its an intermittent problem so I will have to wait for it to happen again and maybe make a video of my testing procedure and readings as proof before I can call out the municipality, because if they pitch up there and test to find nothing wrong (as at this moment) they'll probably think I'm "nuts" like some of the guys on this forum.( I spent some time discussing the problem on the forum last night while it was happening, sharing readings as I measured them and got the feeling that the very helpful members comments suggested that its not really possible).
Thanks for your input, appreciate it!

 

Its an intermittent problem so I will have to wait for it to happen again and maybe make a video of my testing procedure and readings

A good start would be to check the integrity of your neutral connection via observation of the 'cross-line' EMF (i.e. any 240V circuit) during an 'event' -- Stability of the 240V supply under said conditions implicates the neutral connection -- Be warned that a 'bad' neutral may damage 120V loads via an 'over-voltage' condition!

Best regards and, again, good luck!
HP

 

Ground rods that connect to neutral at your breaker box do NOT last forever.
It is a bare copper to copper connection between rod and wire using only a compression collar.

Drive a new rod and make a new connection on clean copper.
Also know that very dry ground, such as you would experience during drought can cause a high resistance neutral conductor condition, and cause voltage fluctuations based on current draw.

 

define "drastic"?
State where/how you are determining there is a problem? Where are you measuring? What tool are you using?

If you are measuring at an outlet in the room then the problem could be anywhere upstream.. And up to an including the distribution box is your issue.. Before that would be the utilities problem and sometimes they will throw a logger on and check it over a period of time..

 

define "drastic"?
State where/how you are determining there is a problem? Where are you measuring? What tool are you using?

If you are measuring at an outlet in the room then the problem could be anywhere upstream.. And up to an including the distribution box is your issue.. Before that would be the utilities problem and sometimes they will throw a logger on and check it over a period of time..

Hi!
Did all measurements at the point of supply entry on the main switch in the db box with a fluke T150 voltage tester

 

Hi!
Did all measurements at the point of supply entry on the main switch in the db box with a fluke T150 voltage tester

Voltage readings at this point of entry ranged between 0volts and 102 V (it is supposed to be, and is at the moment 230V

 

Ground rods that connect to neutral at your breaker box do NOT last forever.
It is a bare copper to copper connection between rod and wire using only a compression collar.

Drive a new rod and make a new connection on clean copper.
Also know that very dry ground, such as you would experience during drought can cause a high resistance neutral conductor condition, and cause voltage fluctuations based on current draw.

In usa ground and neutral aren't same thing cuz neutral is just center tap from transformer which is tied to ground and house wiring both so you still have neutral if you lose ground.

 

Is your incoming supply via underground cabling or overhead cables? If overhead, can the cables at any point be touched by tree branches (which can cause intermittent shorting of line to neutral, or leakage from line to ground)?

 

Voltage readings at this point of entry ranged between 0volts and 102 V (it is supposed to be, and is at the moment 230V

If you checked it before main house breakers its utilities trouble and you should call right now cuz is probably arcing which is major fire hazard!

 

yep.. call them immediately.. If your readings are correct then its already arcing and a fire/total loss of electricity is soon to follow..
But its their problem not yours..

 

I have yet to see the country of origin, although the problem could apply universally the distribution/measured voltage will be different according to country?
Max.

 

Voltage readings at this point of entry ranged between 0volts and 102 V (it is supposed to be, and is at the moment 230V

If you checked it before main house breakers its utilities trouble and you should call right now cuz is probably arcing which is major fire hazard!

yep.. call them immediately.. If your readings are correct then its already arcing and a fire/total loss of electricity is soon to follow..
But its their problem not yours

FWIW I wish to add my voice to those of @Aleph(0) and @mcgyvr --- Don't await recurrence of the malfunction! - Please report your observations ASAP! Additionally, please be advised that transformer explosion is possible in the event of internal arcing! ('Praise' be to supplanting chlorinated dielectric compounds with combustible hydrocarbon substitutes)

Please take care!

Best regards
HP

 

FWIW I wish to add my voice to those of @Aleph(0) and @mcgyvr --- Don't await recurrence of the malfunction! - Please report your observations ASAP! Additionally, please be advised that transformer explosion is possible in the event of internal arcing! ('Praise' be to supplanting chlorinated dielectric compounds with combustible hydrocarbon substitutes)

Please take care!

Best regards
HP

Thanks for al the input and advice, I really appreciate it.