Increased voltage!

[prateeksikka]

hi all!
today i noticed a strange phenomenon.
when i dip the grounding wire of my household in water the line voltage increases in magnitude .
how could that be?from where does the excess energy comes?
thanks in advance...

 

[MP1]

Hehehehe...you are playing with fire, my friend.... ;D

I am just curious, but what ever inspired you to stick one of your mains wires in water?  :

MP

 

[jstevenperry]

Really? What were you thinking?

 

[Alun]

The earth wire should be connected to the water main where it enters your house do dipping it in water shouldn't make any differance.

Anyway you're pretty stupid for playing around with the mains like this what are you trying to acheive? Death?

 

[Decade]

You could connect the mains earth to a waterpipe but these days water pipes aren't always conductive all the way to the pump station and water is a bad
conductor, isn't it? I think that if all pipes are conductive they got to be burried in soil with high conductivety to make a perfect ground.
Here's what happened to me, for twenty years ago I made a good ground for my antenna tower, burried down 2sqr meters of copper in real wet clay and the ground was perfect a good friend from the power company measured it up don't remember how everything was done, anyhow this ground was connected  through the shield of all cables going in to the house and my earth was automatically connected to the distributors earth.
The transformer located few hundreds meter from my house was strucked by lightning and the ground at the transformer was burnt off.
So what happened?  My ground was shared by other households so my ground went hot like h***  ;D

 

[Alun]

Shame about your ground decade, but it wouldn't have been very good either if the appliences connected to it weren't connected to the electrical distribution earth and a fault occured causing your earth (and all metal cased appliances connected to it) to become live.

Even if the water main isn't metal, the pipes in your house probably are and they're always earthed and so are the gas/oil pipes. All large metal structures are earthed in a building where an electrical system is present for safety reasons, the training centre I used to attend had a metal roof and frame - both had earth connections.

 

[Decade]

Hi Alun!

You are right, well... think my neighbours didn't know that their lifes was dependent on my ground  . At that time All appliances (that should be) in my house was connected to safety gnd.
When things like that happens it could end up with several serious accidents.
In my house (living on the country side) there is no special ground for water pipes, the only thing that connect them to mains ground is through couple of pumps.
At least not here are water pipes a good ground because every joint is sealed with teflon tape or lin and linseed oil, I wouldn't put my faith on them as a good ground.
Concerning the ground I think for new installations it is exactley as you say Alun but for old houses it's another story I guess.
About roofs, they'll make some kind of virtual ground because of its size, remember when I was installing an tv antenna, with one hand on the roof and the other touching screen of the coax I could feel that there was a small difference in potential eventhough a tv isn't connected to safety ground, guess there is aways some leakage through cables and other components to chassie ground.

 

[Alun]

As far as virtual grounds it depends on the frequency, as far as DC is concerned a roof is floating (if it doesn't have a direct ground connection) but at RF it's a totally differant story due to its capacitance.

 

[MP1]

the training centre I used to attend had a metal roof and frame - both had earth connections.

Hmmm....that is strange. Grounding the metal roof would make it a good lightning rod during thunderstorms. I would have left the metal roof floating. Of course, all of the plumbing vents that come out of the roof are all metal pipes with a good ground, so you still need a good lightning rod for protection.

MP

 

[ante1]

Hi Guys,

A TV set doesn’t have a ground lead but still the chassis sometimes carry’s mains voltage. If it does just pull the plug and insert it again the other way and the chassis is “grounded” through the neutral lead.  (Well, at least where I live)! 8)

 

[Alun]

Hmmm....that is strange. Grounding the metal roof would make it a good lightning rod during thunderstorms. I would have left the metal roof floating. Of course, all of the plumbing vents that come out of the roof are all metal pipes with a good ground, so you still need a good lightning rod for protection.

I can't remember whetehr it had a lightning conductor or not, but I think it'd be more unsafe to leave it floating because a higher resistance to earth would mean more power would be dissipated when lightning strikes, if it's grounded then all the power would be safely sent to earth.

 

[prateeksikka]

the topic deviated!
Actually i had read about an experiment which people in rural areas of our country do ...
in india mains voltage is 230V(standard) but in rural areas it falls to say 130V which makes the people impossible to run their appliances.
they generally put the ground wire in wet mud(soaked in water) and voltage rises to 230! and believe me its true!
can anyone suggest a mechanism behind this(rural people dont know the logic! ofcourse!!!!!) ;D

 

[Decade]

Hi Ante!

The tv-set has two seperate grounds, one for the mains rectifier and one for the secondary side of the smps which is same as the chassie gnd. There is not any real ground before the mains rectifier, minus side of the mains rectifier is usually connected to the secondary side of the smps through a high ohmic resistor in parallel with a capacitor approx. 2,2nF that's the only connection to the chassie itself, it is isolated from the mains by doing so, minus of the mains retifier is ofcourse connected to primary side of the smps  ;D.
But in the good old days when the lovely tubes still was popular it wasn't unusual that the chassie was connected to the mains.
Ante you got to have an old tv, let me know if you want my old LUXOR I have in the basement?  ;D

Sorry prateeksikka the increased deviation  ;D

I guess that either the ground resistance at transformer is to high or the power company is just simply to meagre to run a conductor with proper size ;D
Can't think of any other reason.

Hi Alun!

Yes I know for DC there isn't anything lika virtual ground at the roof but for AC I think, there is always a mains field that will be induced into any metal.
For RF the roof will more or less act like a groundplane.
I'll measure that tomorrow

 

[MP1]

sorry to deviate from the original topic...

I can't remember whetehr it had a lightning conductor or not, but I think it'd be more unsafe to leave it floating because a higher resistance to earth would mean more power would be dissipated when lightning strikes, if it's grounded then all the power would be safely sent to earth.

The roof would become the lightning rod. This would mean that all of the lightning current would rush through this metal roof on it's way to ground. Any wood or other flammables connected to the metal would go up like stick matches. Even a lightning rod on a metal tower must cause the electricity to go straight down to the earth rod or all the equipment on the tower is toast.
Simply grounding the roof is no protection, either. A good lightning rod connection is a large gauge wire which goes straight to the ground with no bends or curves. Lightning does not take curves very well. It tends to go straight. Whatever is in the path will be effected.
I see a lot of bad grounding protection of equipment outdoors. The only thing that saves it, is the fact that lightning has never hit it.
In such a case as this roof, I suggest no ground connection to the roof and use a lightning rod which is significantly higher than the roof. Electricity will take the easiest path to ground. If the roof "must" be grounded for some other reason, then it will depend upon the lightning rod to take the blow.

MP

 

[ante1]

Hi Decade,

I don’t do TV-sets anymore but you are wrong about only the tube era and as I told before “the chassis sometimes carry’s mains voltage”. The voltage in chassis phenomena was way into hybrids and semi sets too, not on all but quite a few. However I don’t know about Japanese sets since I did not touch that stuff back then. 
 
And you know what you can do with that old Luxor set! ;D ;D

 

[Decade]

Hi Ante!

Yes you are right about that those chassies carried mains voltage, these days chassie ground is only connected to secondary side of the smps and the primary is decoupled to chassie ground and will therefore carry a small potential.
If the mains were grounded to chassie it would blow fuses once in a while depending on how you insert the plug, the chassie would be grounded through the coax shield, before the antenna connector was decoupled through capacitors to prevent the mains from going out on the shield of the coax.
I'll be glad to get rid of the tv I'll send you my LUXOR tomorrow  ;D ;D

 

[audioguru2]

I still have my very 1st colour TV. It is a 1971(?) 27" Philips hybrid and it still works fine!
Its degaussing circuit scares my wifey and dog. Its dripping electrolytics scare me.
I haven't used it for about 5 years so I should remove my descrambler circuits and also get rid of it. ;D

 

[Decade]

Don't throw it Ante might be interested

 

[ante1]

I remember when dad brought home the first color set, it was just before the 1968 Olympics in Mexico. The color technique was not really ready by the time and when somebody dressed in bright read colors moved fast the color smeared over the screen. It was a Philips set and it kept the room warm in winter time too. ;D