# Strange Voltage On Line Connected To NOTHING??



## cdnelectrician

belldogs said:


> Hi everyone,
> 
> Im a second year apprentice linesman in Australia, i recently came across something that completely confused the **** out of me and everyone i work with. I'll try and explain what happened as briefly and as best as i can, with as much detail as possible.
> The job was to to run a new two phase, three wire line, one span from the transformer. We had an outage for the job and everything went relatively smooth. We ran the new conductor and tensioned it. So at this point i need to make it very clear that this new line isn't connected to anything, its just aluminium conductor hanging in the air. We set the transformer up for two phase and corrected the tap settings. At this stage we are ready to turn the juice back on and commission the transformer.
> We re-energise the transformer and head back up to complete the commissioning tests. I'm not sure what tests are done in the states but the first thing we do is test to see if we have voltage off the neutral bushing of the transformer, we do this by using a voltmeter with one lead connected to the earth and the other to the conductor we are testing. The reading is zero volts, (as you would expect a measurement from a neutral conductor off a transformer to earth should be zero) so all is good up to this point. The next test we perform is to measure the neutral conductor thats hanging in the air to earth, now this is where the really strange part comes into it. This conductor that isn't connected to anything, it is just a piece of wire hanging in the air, has 180 volts! How the **** can a wire completely suspended in air have a voltage of 180??
> Now the first thing we thought was that it must be a static charge built up in the line so we tried to dissipate the charge by connecting it straight to earth, we then tested again. It still had 180v! we thought **** this volt meter must be ****ed! so we got another one and performed the same test. Still the same result, 180 ****ing volts. Don't tell my employer but we eventually came to the old ozzy conclusion that "she'll be right", and we connected it up anyway. So we did and there were no adverse affects. the phases had the right voltage and everything else tested out fine.
> So the question i'm asking all of you is why the **** did this line that was merely suspended in air have a voltage of 180 that would not go away?
> 
> Im happy to answer any questions.
> Thanks,
> Belldogs


Was the conductor in question strung near a HV line? Only thing I could thing is it was induced voltage?


----------



## Big John

Have some trouble following that story, but it sounds like you had a disconnected neutral running parallel with live overhead, right?

You're gonna get induction into the ungrounded line. That's why you always put safety-grounds on de-energized overhead.

EDIT: I didn't see you were an apprentice lineman. Then you really need to talk to your journymen about induction and how to set up a safe-work zone through grounding and isolation. 

At high voltages, or long distances, induction can be severe enough to kill you. You were lucky this time it was only 180V.


----------



## erics37

Sounds like ****ing phantom voltage to me?


----------



## McClary’s Electrical

Read it with a meter with a low-z function.....


----------



## belldogs

thanks for the replies,

Ok so i have to mention that we performed the work to safety standards, the HV was isolated and it was short circuited and earthed. It was only when we re-energised the line and we were performing our tests (with rubber gloves) that we noticed the problem.
And yes the new line we had run, runs directly beneath the high voltage line, so could this explain why the voltage was constant and did not dissipate when we connected it straight to ground?


----------



## belldogs

oh and sorry about the duplicate, i first posted in general electrical then realised it was more appropriate in this one.


----------



## 8V71

belldogs said:


> thanks for the replies,
> 
> Ok so i have to mention that we performed the work to safety standards, the HV was isolated and it was short circuited and earthed. It was only when we re-energised the line and we were performing our tests (with rubber gloves) that we noticed the problem.
> And yes the new line we had run, runs directly beneath the high voltage line, so could this explain why the voltage was constant and did not dissipate when we connected it straight to ground?


It sounds very normal and I would think that you would run into this quite often. How much distance were the lines paralleing each other? Where were you measuring the 180 volts? When you say straight to ground does that mean the earth itself?


----------



## belldogs

8V71 said:


> It sounds very normal and I would think that you would run into this quite often. How much distance were the lines paralleing each other? Where were you measuring the 180 volts? When you say straight to ground does that mean the earth itself?


There was about 3 to 4 metres between the lines, the 180 volts was measured between the conductor and earth and yes straight to earth.


----------



## boora2

Interesting,but where in Straya do ya use 2 phase,only saw that once bout 32yrs ago when working in US,Philadephia,Incoming supply to this factory was 13.2kV to what this US sparky called Scott transformers.


----------



## hardworkingstiff

boora2 said:


> Interesting,but where in Straya do ya use 2 phase,only saw that once bout 32yrs ago when working in US,Philadephia,Incoming supply to this factory was 13.2kV to what this US sparky called Scott transformers.


Something tells me it's 2/3 of a 3-phase transformer bank.


----------



## belldogs

yeah two phase isn't something you see too often here, i'm not really sure why it was needed actually, it was just in the design specifications.

And no it wasn't a 3phase transformer bank, we don't have those here. There are only 2 types of pole mounted transformers here.
1) single phase transformer- can be connected in either single phase or 2 phase
2) 3 phase transformer- i've only ever seen delta - Y

I haven't heard of a scott transformer before
Our distribution HV line is 11kv, and LV is 240v or 415v


----------



## 8V71

So anyway...you have inducted voltage on the wire with little/no current behind it. The soil itself (earth) is not a good conductor so you are still reading 180 volts. Does this sound like what is happening?


----------



## belldogs

yeah i think you're right, i just find it hard to believe that a conductor hanging 3 m below would have an induced voltage that high


----------



## gnuuser

its not uncommon to see this 
ive seen phone lines 4 feet below a hv line induce a voltage (40 volts) with enough current to tickle you a bit
(phone company guy was new and put the line too close):laughing:


----------



## austliney

was there no MEN at the transformer or end of line?


----------



## RIVETER

If the secondary of the transformer is grounded...that is, taken to the earth at the base of the pole...what would one expect if you tested a conductor of the same transformer to earth.


----------



## Five-oh

Emf field was a factor, See it all the time...


----------



## Rockyd

If it's not grounded in linework, it's live. If there's any doubt, this was at our job site - looks like potentially working outside the grounds. Don't know for sure, as we were down in the yard....jut considering all possibilities.


----------



## Frizratz

Sorry, I know this is a month old but I was curious......

Did you happen to test the un-grounded conductors also ?
Did you use a Fluke and did you try a solenoid type, wiggy, tester by any chance ?


----------



## josh5879

Frizratz said:


> Sorry, I know this is a month old but I was curious...... Did you happen to test the un-grounded conductors also ? Did you use a Fluke and did you try a solenoid type, wiggy, tester by any chance ?


try almost a year old


----------



## just the cowboy

Didn't you ever see a fluorescent light glow just being near (10-20 ft away) from HV. Touch the pins on one side and wave it in air, it will light by induced voltage.


----------



## maddhatter

My concern is that phantom voltage / ghost voltage completely confused you and everyone you worked with... I would have thought awareness / mitigation of induced voltage would almost be the second thing you'd do as a linesman, up there next to isolation of the HV supply. Certainly something that should have been covered during your prestart / safety training...


----------



## Frizratz

josh5879 said:


> try almost a year old


Thanks for pointing that out.
I was looking only at the post ahead of mine, about a month ago.


----------

