Swimming Pool Zapped by "Stray Voltage."

[k4kyv]

A family has been confronted all summer with a pool problem that's apparently not uncommon: stray voltage.  Three months later, the specific source of the low-level electrical shocks still hasn't been determined, although it likely stems from a nearby utility pole transformer.

"On June 10, we noticed we were feeling an electrical tingle when standing on the pool deck, and reaching into the water," said the pool owner.

The power company was contacted.  The pool owner was told that the transformer had been inspected and there wasn't a problem.

"On June 22 my mother was on the pool deck touching the water with the aluminium cleaning pole, when she felt a very painful shock and heard a noise that sounded like a cannon going off," when a fuse on the utility transformer tripped and left all of the homes on the road without power.

The transformer was replaced, but that didn't fix the problem either.

The ground wire, main and neutral wires for the house were disconnected from the utility company's electric lines and the voltage remained at the swimming pool.  But when the utility company's neutral wire was removed from the transformer, the voltage went away. The utility company says they are unable to locate the problem.

http://www.theleafchronicle.com/apps/pbcs.dll/article?AID=/20060909/NEWS01/609090307/1002

[wa1knx]

this is very common. When I lived in berlin ma, up a 900' drive  I had the same
thing, grab the water spiket bare foot and zap! there was a voltage there suffcient
to feel. the power companies try to keep the neutral line neutral but it doesn't
always work.  I would suspect laying a really good ground system around your
home and pool might bring up the local ground voltage to  match the neutral's
voltage, thus making it a relative neutral might work. I just lived with it..

[Bacon, WA3WDR]

That sounds like some massive unbalance in the high voltage feed, that is pulling the ground way off center, and this is causing voltage gradients in the area surrounding whatever ground stake the power company is using.  The report of a jolting shock at the same time that the fuse blew supports this.  Maybe they are near the end of a very long single-phase extension run.  Of course it doesn't take much to feel something with wet hands on an aluminum pole into a swimming pool, but gee...

Of course, I remember what happened when I ran the 2-813/2-810 rig on 120V single phase power.  I would key up and modulate, and the neighbors had some lights dim, and other lights got brighter!  So I guess it's possible to pull the neutral off center with loads.

Did the Consolidated Edison power problem in Queens, New York make national news?  I saw it on Google news, anyway.  It seems that there was some problem that nobody could figure out, and it kept power off for a week or so during the hottest part of the summer of 2006!  I'm not sure if it has been completely repaired even yet.

[wa2zdy]

Of course, I remember what happened when I ran the 2-813/2-810 rig on 120V single phase power.  I would key up and modulate, and the neighbors had some lights dim, and other lights got brighter!  So I guess it's possible to pull the neutral off center with loads.

This is usually a sign of a bad neutral, mostly a loose neutral connection in the breaker box or outside.  This of course results in the two sides of the house being a series circuit.   When something big sucks down surge starting current, like a refridgerator or your rig, it draws the surge through the other side of the 230 circuit thus brightening the lights rather than dimming them.

This is considered an immediate health and fire hazard.  I had it happening in an apartment I lived in a few years ago.  I gave up on getting the super to look into it and took the cover off the breaker box myself and found the neutral indeed loose in the box.  Tightened it up and problem solved.  Went through a few light bulbs until it was corrected.

[W1ATR]

Sounds like the local utility is feeding these people a bunch of BS. They know EXACTLY what causes "stray voltage" to appear at things like pools and wells, metal buildings, etc. (That's why the problem went away when they pulled the neutral at the transformer.) These people must be far from the substation, as the farther down the line they are, the more voltage appears on the primary neutral. I think they,(the utility), are supposed to have something like 4 or 6 ground rods on the primary neutral per mile from the sub. It's standard practice to for the util. to connect the primary neutral to the secondary neutral across the transformer and use to customers electrical service ground rods to help sink some of that voltage to ground and help keep the neutral near zero. The pool is acting like a low resistance shortcut for the current flowing thru the soil back to the sub. All they need to do is go back down the line and install some fresh ground rods on some of the poles, or fix the existing ones, and this problem would vanish.

I learned this from a customer that was having the same problem with a large koi pond and they blew him off and told him the pond needed to be grounded. (What do you mean, it's a pond, it's IN the freaking ground.)[I was laughing my butt off the way he was telling the story.] Anyway, he had to get an electrical engineers report and finally take the util. to court before they would go out and fix the grounding fault.

[k4kyv]

This is usually a sign of a bad neutral, mostly a loose neutral connection in the breaker box or outside.  This of course results in the two sides of the house being a series circuit.   When something big sucks down surge starting current, like a refridgerator or your rig, it draws the surge through the other side of the 230 circuit thus brightening the lights rather than dimming them.

This is considered an immediate health and fire hazard.  I had it happening in an apartment I lived in a few years ago.  I gave up on getting the super to look into it and took the cover off the breaker box myself and found the neutral indeed loose in the box.  Tightened it up and problem solved.  Went through a few light bulbs until it was corrected.

The exact same thing happened to me right after moving here about 25 years ago.  We had the electric service upgraded and a new 200-amp Square D breaker box installed by a licensed electrician, and had the job inspected and OK'ed by the local electrical inspector.  About a year later, I fired up my KW transmitter one day, and as soon as I hit the transmit switch, the house lights lit up like flashbulbs.  I immediately shut everything in the house down, took the cover off the breaker box and looked inside.  All the neutrals to the individual  circuits were tied to one of two bus bars, which were in turn connected to the main neutral wire from the meter and the ground rod at the entrance.  I could see heat damage on one of the bus bars.  Turns out, the main bus bar was indeed directly bonded to the incoming neutral wire, but the second bus bar was electrically connected to the main one through nothing more than the the rivets that fasten each of the bus bars to the steel box.  I could see hot spots at rivets.  I turned the power back on, and I could wiggle the secondary bus bar and actually see sparks around those rivets.  Each bus bar had a few blank holes, so I took some #10 bare copper and bridged the two bus bars together by inserting one end in a blank hole on one busbar and the other end into a blank on the other one.  I think I ended up using 6 or 7 separate wires, so I was pretty sure the second bus bar was firmly bonded electrically to the first one.  I am still using that breaker box.

Of course, what happened is when I hit the plate switch, the KW transmitter, which runs on 110V single-phase, pulled a near dead short across one side of the line, so that nealy all the 220V appeared across the opposite side.  Luckily, I didn't have the TV or other sensitive electronic devices running at the time, no computer in the house, and my hollow-state receiver and other station equipment was able to take the momentary voltage surge without damage.

I suppose I could have hired a hotshot lawyer and sued Square D, claiming extensive damage to the electrical system and appliances in the house, but that would have been a huge hassle, plus leaving the box unrepaired and power off for days until the insurance adjuster could have inspected it, so instead I just fixed it myself (about a 30 min. job) and went on about my business.

As for the pool problem, I have heard of people getting electrocuted merely standing close to a metal utility pole and touching it.  This was due to a potential gradient in the earth, resulting from a severe unbalance, such as an open neutral, causing the earth ground to pull enough current to create a  lethal voltage drop in the soil immediately surrounding the pole.  The person happened to be standing on the ground, barefooted or in wet shoes, just far enough away to create a deadly potential difference between himself and the grounded pole.

The question in this case with the pool is, where is the ground fault that is causing such a severe unbalance?  The article says they completely disconnected everything going into the house, including both hots and neutral and the problem persisted.  But disconnecting the neutral from the xfmr stopped the stray voltage.  Sounds like a neutral has opened up somewhere nearby, and the earth is providing 100% of the return path from that transformer, not the neutral wire that goes with the 11 kv line.  (I am guessing you still call the grounded conductor that goes with a single-phase medium-voltage distribution line, the "neutral").

If everything is properly grounded, the neutral is functioning and there is no ground fault associated with a power circuit, there is no reason for any significant voltage to appear on nearby grounded objects.  Sounds like someone doesn't know what they are doing.

[kd5cpl]

Hi--

If  disconnecting the neutral from the pole transformer secondary and the ground at the pole caused the stray voltage to go away, they need to look at the service going into other homes on the same transformer. Somewhere there is a bad or overheated connection in the neutral wire from a house (or whatever else) that is connected to the same transformer. If the stray voltage is coming from the HV distribution side of the system, disconnecting the neutral should not kill the stray voltage in the pool. It seems that they could figure this out easily enough.

I once has the neutral going to a house I lived in go open (burned in two) thanks to utility workers stripping 1" of insulation from each 110V line right in the middle of the drip loops where the overhead line was attached to the house. They had done this to clip on leads to a chart recorder after I had complained about unstable voltage and brownouts. (They told me nothing was wrong on their side, yet the problem remained until the pole transformer went up in smoke about 6 months later and got replaced.) Anyway, a windy storm got those drip loops swinging into each other and one of the bare spots touched the aluminum neutral/suspension wire, which lost the battle when things got hot. I got home and found lights, etc. behaving oddly, depen ding on what else was turned on. Went outside and looked and saw the problem. Called the utility, they said they would have someone out the next day. I turned the main breaker off, checked across the open with a meter to verify no stray voltage, then connected the ends together with a splice lug since I didn't want to spend the night in the dark if I didn't have to. The next morning the utility supervisor asked ME how the bare spots got there. He said their workers would never leave a conductor stripped like that. He also said that those bare spots looked like someone had tried to steal unmetered electricity from the utility. I always wondered how many times they inspected the lines AND the meter seal after that.   It's a wonder that that  problem didn't cost me a refrigerator, a/c compressor, audio gear, etc.

Even if the problem in the pool incident ends up being inside the breaker panel in someone else'e house other than the pool owner, you'd think that the utility could figure it out.


73, Gary

[wa1knx]

your lucky Gary,
       that happened to my mom, lost the neutral to the pole. your small house
ground is not much of a return, and the one side of neutral must return via the
stuff connected to the other side! thus put on a electric heater on one side and
a 60w bulb on the other, and pop goes the bulb! we were pretty lucky as
well nothing go damaged once we figured it out.

Dean

[N9NEO]

I seem to recall I study that was ongong while I was at college..  Apparently stray voltage is common on farms (rural areas) and cows are normally subjected to electric shocks.  I think the study had to do with milk production.  I built the gear that did the shocking.  I was reluctant at first because I don't have anything against cows.  I think cow milk is a very nice thing to give to children, and I really like a nice thick prime rib from time to time.

So point is farmers are also very familiar with this problem.  And I agree that utility knows exactly what they are dealing with.  If they are dragging feet I wonder if it is because it might not be a simple fix.

regards,
Bob

[KB2WIG]

                  "I don't have anything against cows."
 Yes, cows are effected by very low voltages... If you look closely at one, you'll notice that they have a tendency to bury each foot (hoove) into the ground, which is usally full of cow urin..  They have a fine ground connection. Although I've fed them mash, I've never tried to load one up....  Anyways, that big, wet cow tounge gets zaped on metal stanchions, water troughs, etc. Not good for mother cows milk..... As Bob said, the utility knows whats happining and probably don't care.  DLW - delay, linger wait. Hope that the cus timer will get tired and fold..., W2WME, had a multi year run in with the local power co. He was in a rural area, at the end of the line. His Voltage ran anywar from 90 to 135( as close as I can remember). It took a few years for NiMO to give him a new pole pig....   klc

[Jim, W5JO]

In the telephone industry one of the training seminars they receive is to check for stray voltage at the pedestal where interconnections are made in rural areas.  Seems as if this is not an uncommon problem and workers can be electrocuted if they try to open a pedestal with voltage on it.