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[Articles Home]  [Add Article]  

Power Line Misunderstandings

Larry Kendall (K5END) on July 16, 2008
View comments about this article!

Deadly Misunderstandings About Power Lines

The voltages on distribution power lines (typically 1200 V to 35,000 V) are higher than most people can comprehend. Transmission power line voltages are even higher, in the hundreds of thousands of volts. One need not come in direct contact with power lines to suffer electrocution. Here are reasons why.

Point 1. Air has an electrical breakdown point. If the electric field, or voltage over a given distance, exceeds the breakdown voltage/field property of the air, it will arc. That is why there is a MINIMUM distance to respect. Ignore it and you will pay. The higher the voltage, the greater the distance you need to respect.

Point 2. An object in direct contact with the power line need NOT be a conductor for current to flow across it. At sufficiently high voltage (and the power lines are sufficiently high in voltage) flashover can occur. Moreover, impurities (dust, pollen, etc.) on the surface of the object can enhance the flashover. Kite strings are an example of a "non-conductor" that conducts quite well.

Point 3. Consider the spark that occurs when you unplug the vacuum cleaner from the outlet when the motor is still running. That is because of the amount of current at the time, the motor's and other inductances and some very straightforward physics: Emf = L di/dt. Oversimplified, if you try to interrupt that current, voltages get very high as the current "attempts" to maintain itself and the voltage/electric field becomes higher than the breakdown level of air. Now consider how much more current the power line can supply! Once you've introduced a path for that current, no matter how briefly, you've invited an electrical Tsunami. And it won't stop flowing until it is good and ready to stop.

Point 4. Another hazard: power lines have switches located at the tops of the poles. Many of these are monitored and controlled remotely (by radio!) Many are programmed to open when a problem occurs "downstream." These switches can and will open, repeatedly, without warning. They are designed to break the arcing that will occur when the switch is opened, but nothing ever works perfectly all the time. Arcing can occur several meters through the air for the better part of a minute under the right conditions. If you are nearby, it may reach out and touch you.

Point 5. Periodically along the lines the poles have "pole bonds," ground wires that literally ground the overhead ground to mother earth. You can unwittingly parallel yourself to this harmless-looking ground wire. Worse, it is a prime target for copper thieves who cut the conductor a few feet above the ground. Then you have an open circuit to ground. If you complete that circuit, your loved ones may grieve.

The utilities refer to a shorted circuit as a "fault." When a fault occurs, it sounds like a cannon. Squirrels, snakes and tree limbs cause most faults. Cars hitting and breaking the utility poles cause a few as well, and often result in a fire. Sometimes the faults are would-be copper thieves (not knowing that the conductors are aluminum.)

Stay well away from the power lines. Stay away from the poles. Don't hang around under the poles or lines. It is a silent hazard. It only takes ONCE. No second chances, no do-overs, no repeats.

Member Comments:
This article has expired. No more comments may be added.
 
Power Line Misunderstandings  
by KU4UV on July 16, 2008 Mail this to a friend!
Let me be the first to say, excellent article, well written and very inforamtive. I guess I am probably kind of on the younger end as far as the median age of ham radio operators go, being 33 years old. It seems that almost everyone has some sort of story or "near-miss" incident to tell regarding electricity or lightning strikes. I have several I can think of myself. Some of them I saw or was involved in. Other incidents happened to family or friends. About 20 years ago, my dad was playing one summer afternoon in Indiana. A lightning bolt struck nearby, and he figured it was time to head toward the club house. He reached to pick up his putter which was lying on the ground. When he grabbed the putter, he received a quick electrical jolt. I'm not sure what caused this exactly. Maybe someone can let me know. I would assume the lightning energized the putter enough that even though it was lying on the ground, there was still some charge left in it. I guess when my dad picked it up, he completed a better path to ground, and thus received a shock.
Our local power company, Kentucky Utilities used to put on a power line safety demonstration every year at one of the local hamfests. The would back-feed a HV electrical transformer, producing something like 2000 Volts of electricity. They would take a Polish sausage and put it on the end of of lineman's pole. After the voltage went through the sausage, the thing was still smoking, and was essentially charred. The guys giving the demonstration explained how electricity mainly burns the body on the inside, and how the human body is much like the sausage in that it is basically meat, water, and salt. The also blew the fuse on the line to show what happens when a fault occurs. The bang is deafening. One thing that I was puzzled by though. One of the linemen giving the demonstration told a story about two men where working on a power line. One of the men was in a bucket, and the other man was on the ground, if I recall correctly. The man in the bucket was somehow killed by the high Voltage. The other man claimed that he never touched the power line with with the bucket. The man giving the demonstration told us that, "electricity does not jump." I had always thought that electricity could arc, or "jump" if the Voltages were high enough, even though you didn't make direct contact with the HV line.
Several years ago when I was working at the ABC affiliate here in Lexington, I remember hearing about a reporter in California who has hurt by high voltage. It seemed the reporter was covering a trial with a videographer, and the videographer had set up the live shot van near at the courthouse. There were some HV power lines overhead, and the videographer apparently did not noticed them. When she went to raise the mast on the van, the pole either touched the power line, or became close enough to arc over. The reporter and videographer both were hurt. The reporter ended up losing some fingers and toes if I recall correctly. The videographer received a shock, but was apparently unhurt otherwise. There are devices on live trucks that are desined to automatically lower the mast if a high voltage is detected. Apparently, this particular van was not equipped with such a device.
You were also correct about the copper thieves. We had an incident here in Kentucky just about a month ago of someone found dead trying to steal copper for a substation. Several years ago, I was working at our statewide PBS network center here in Lexington. One day, it was really windy outside, and the lights in the building kept flickering. It seemed they did this all day. Someone mentioned that the lights kept flickering. I informed them that this was to to the trees hittiing the power lines because of the high winds, causing them to arc. Great article. I am sure others have stories they can tell about thier experience withn high voltage lines.

73,
Michael KU4UV
 
Power Line Misunderstandings  
by N8DV on July 16, 2008 Mail this to a friend!
Excellent article. At the Hamvention, Dayton Power and Light would put on a demonstration complete with mini-power pole, transformer and line. The demo would show what a live tree branch would do if it was energized by a power line. Also the demo explained the transmission of how electricity gets from the generation plant to our homes. Dayton Power and Light also illustrated many safety tips regarding power line safety. The demo has been on for a number of years. It was always well attended. Let's petition the Hamvention committee to get the forum to return to Hamvention.
 
RE: Power Line Misunderstandings  
by KB9TMP on July 16, 2008 Mail this to a friend!
With KU4UV talking about the safety demos reminded me of our local ones. The fellow from the local REMC that was the lineman that did the demo had an accident himself just a few years ago. He ended up loosing a hand and foot to that accident. So if the 'experts' on power line safety can be injured by a power line, it's going to be even easier for the rest of us.

73 de KB9TMP
 
RE: Power Line Misunderstandings  
by N4CQR on July 16, 2008 Mail this to a friend!
Nice artice.

Speaking of utility electric, this video has been around for quiet some time on several different websites and has eventually found it's way to YouTube:

http://www.youtube.com/watch?v=hIkNY5xjy5k

There are several stories floating around (folk and otherwise)about it but the point is the energy displayed. There is a video of a recloser operating but I can't seem to find it.

73 Craig

 
RE: Power Line Misunderstandings  
by K0BG on July 16, 2008 Mail this to a friend!
What's tragic about this is, it came too late for two folks in Kansas City, Kansas this past Saturday. I didn't personally know the men, but having grown up in KC,KS, I knew several of the amateurs who reported the story to the ARRL. As a result, I was sent a photo of the installation.

It was a tripod roof mount with a Comet base station antenna mounted on it. The distance from the antenna to the 7,620 volt power line was less than the length of the antenna; about 5 feet.

Should they have known better? You bet, but sometimes folks just don't think about what might happen, if....

Alan, KBG
www.k0bg.com
 
RE: Power Line Misunderstandings  
by K5END on July 16, 2008 Mail this to a friend!
quote, "What's tragic about this is, it came too late for two folks in Kansas City, Kansas this past Saturday. "

I wrote the article Monday evening after having read the news on the victims. Eham processed and posted the article on the site practically overnight.
 
Power Line Misunderstandings  
by K4LJA on July 16, 2008 Mail this to a friend!
Great. Thanks for the safety reminder. Here's a
pretty good safety video link.
http://www.youtube.com/watch?v=2_4gsPe7BuM&feature=related
73 -- Randy , K4LJA in Monroe, Louisiana
 
A Massive Power Line Misunderstandings  
by N3QE on July 16, 2008 Mail this to a friend!
The firemen backing away as the rain gutters on the houses do their boom-boom-spark-bang thing, while hundreds of feet away the 38kV line is shorting to all the household 120V power lines with continual "buzz-buzz-burst" cannonfire, all without any breakers tripping, is very impressive:

http://www.youtube.com/watch?v=lEAtWiUGeiA
 
after 2 duds we have an informative article  
by N8NSN on July 16, 2008 Mail this to a friend!
Great article Mr. Kendall. Very informative and much appreciated.

Lightning could stand an informative article like this one. I think, if i am not mistaken, yesterday on the news a statistic was stated that 4000+ people a year are killed by lightning. Not sure whether that was world wide or just nation wide. I just wonder how many, if any, of the 4000+ lives could have been saved by observing any safety related factors concerning lightning strike prevention.


There are 3 things I have heard about lightning. I want to know if they are true. Perhaps, someone here knows or has witnessed these things first hand.
1) I have heard that before lightning strikes, the ground, in the area of the preeminent strike, puts out a type of static "feeler". In a sense, the charge between the sky and earth searches out the best spot for the strike before it happens.
2) I have also heard that lightning mostly travels from the ground up?
3) Lastly, I have heard that lightning goes both directions, from the clouds downward as well as the ground upward, and meets in the middle...?

Maybe someone knows of some good websites to read reliable material on lightning, lightning safety and possibly some prevention tips other than "stay indoors".

Thanks again Mr. Kendall.

 
Power Line Misunderstandings  
by NS2K on July 16, 2008 Mail this to a friend!
One other problem is that if a high voltage line is in contact with the ground, because the soil (or pavement) is only a moderately good conductor, there is a voltage gradient radiating out from the point of contact that can be lethal at quite a distance. Just the length from one foot to the other can have high enough voltage to arc through most footwear and into the body.
Because of this, people and animals can get electrocuted even though they are quite a distance from the downed line. I suppose that keeping the feet close together can be helpful, but giving real advice can be difficult as every situation is different. Perhaps someone more experienced can comment further.
 
RE: Power Line Misunderstandings  
by K5END on July 16, 2008 Mail this to a friend!
quote, "One other problem is that if a high voltage line is in contact with the ground, because the soil (or pavement) is only a moderately good conductor, there is a voltage gradient radiating out from the point of contact that can be lethal at quite a distance. Just the length from one foot to the other can have high enough voltage to arc through most footwear and into the body.
Because of this, people and animals can get electrocuted even though they are quite a distance from the downed line. I suppose that keeping the feet close together can be helpful, but giving real advice can be difficult as every situation is different. "

That is absolutely true, and perhaps I should have included it, even though the intent was to focus on antenna safety. Use of the term "gradient" is the best choice.

That raises another point. If a person finds himself in a car accident with downed power lines near or on the car, he should stay put until the responders have determined it safe. Fatalities have resulted when occupants have attempted to step out of the vehicle.
 
RE: after 2 duds we have an informative article  
by K5END on July 16, 2008 Mail this to a friend!
quote, "Lightning could stand an informative article"

Done. Will submit to eham for approval.

In the meantime, here are some main lightning safety points:

1. If you can hear thunder, you are within range of a strike. Lightning can travel laterally for several miles across a clear blue sky before it reaches the ground. Thus the cliche' "out of the blue."

2. The first lightning strike of a storm is as deadly as any other. People seem to think an electrical storm has to "warm up" before it is lethal. Wrong.

3. Lightning ranks second only to floods in U. S. fatalities from natural disasters. Florida has the highest lightning fatality rate--and it's not because of all the golf courses! :-) It is because of the local geophysics. Alaska has virtually zero lightning.

4. The interior of a metal car is a GREAT haven during an electrical storm. This has nothing at all to do with the rubber tires, but is because you are surrounded by a conductor, as discussed in part by Gauss's law in Maxwell's equations.

5. Trees are not great conductors, but are common lightning targets. This results in a plasma "umbrella" flashover in the tree's vicinity. Anyone in the vicinity is subject to injury.

6. The majority of ham antenna installations I've seen (including my own) are not sufficiently protected against lightning strikes. We need to change this.

 
Power Line Misunderstandings  
by TANAKASAN on July 16, 2008 Mail this to a friend!
Thank you.

Tanakasan
 
Power Line Misunderstandings  
by W4VR on July 16, 2008 Mail this to a friend!
Too bad the ham and his son who got electrocuted recently while putting up an antenna did not have a chance to read your article. They could have avoided "death."
 
Lightning  
by K0BG on July 16, 2008 Mail this to a friend!
I apologize for this being a little off subject. I operate a lot while mobile, and in all kinds of weather. I have had my HF mobile antenna struck three times.

The first time nearly destroyed the transceiver I was using. The antenna wasn't DC grounded. The second time I was unaware of the strike until later. The matching coil had been burned into, and probably took the brunt of the strike.

The third time was last year when driving home from Dayton. There were tornadoes in the area at the time, and I was listening to NOAA weather. The strike was one of a series which happened in a matter of seconds. The last one was so loud, had I not had a seatbelt on, there would have been a dent in the roof! It turned the hood blue for a second or two, put a neat little hole in the corona ball, heated the whip hot enough that it bent over 90 about a foot from the top end, and blew the solder out of the shunt coil's connections. Whether that coil saved the transceiver from damage is perhaps moot, but I shudder to think what could have happened without it.

Alan, KBG
www.k0bg.com
 
Power Line Misunderstandings  
by KU4UV on July 16, 2008 Mail this to a friend!
I hope it doesn't seem like I am hogging the forum, but there are a few other stories I wanted to pass along regarding electrical safety. One other thing that the lineman mentioned that gave the safety demonstration at the hamfest was about the safety involved with generators during a power outage. He mentioned that you never want to "back-feed" from a generator into a 110 Volt household outlet if you have a storm or other emergency. He said that what can happen is that it can cause the utility line to be "hot" with the HV coming off of the primary on the line transformer. This creates a dangerous situation for the linemen, because they think the line is "dead," when it is actually still hot, because it is being back-fed by the generator. We had a situation here in Lexington back in February of 2002 where we had a major ice storm. The ice storm began on a Saturday evening around 8:00, and didn't end until sometime early the next morning. When it was all said and done, the entire city looked like a war zone from the downed trees and power lines that had been brought down because of several incehes of ice buildup. I worked at a distribution center here in town for Amazon.com at the time. We were out of work for several days because most of the city was without power. The company had to eventually rent some generator trucks to supply the warehouse with electricity. I was lucky in that my apartment never completly lost power, although the power would go out for a few seconds each day, and then come back on. There was a house here in town that had a power line come down on top of it, or somehow was damaged in the storm. Well, the local power company apparently never checked this, or they were simply never notified that there was still a line on the house. When the power company finally tried to restore power to this line, can you guess what happened? A really nice house went up in flames. I understand there were other house fires in town related to incidents like this. Yes, you certainly have to use some common sense when you are dealing with electricity. It is a very unforgiving force that a lot of us take for granted until we are forced to live withought it for whatever reason. Be careful gang!

73,
Mike KU4UV
Lexington, KY.
 
RE: Power Line Misunderstandings  
by N4OI on July 16, 2008 Mail this to a friend!
Since someone already "arced" the subject from power lines to lightning -- Is an attic antenna in any way more prone to lightning strikes than the house itself? Does the attic antenna increase the probability of a strike to the house? Just curious. 73 de Ken N4OI
 
RE: Power Line Misunderstandings  
by K5END on July 16, 2008 Mail this to a friend!
quote, "Since someone already "arced" the subject from power lines to lightning -- Is an attic antenna in any way more prone to lightning strikes than the house itself? Does the attic antenna increase the probability of a strike to the house?"

That's hard to answer without examination of the individual case, but the collective belief is that an attic antenna does not influence *whether* lightning will strike the house. My opinion is that the answer is too general, but you know what they say about opinions.

However, the presence of the antenna and its transmission line to the radio, which is in turn connected to a power source and an operator may influence what happens inside the house or to the operator when lightning strikes.

Lightning and power line safety are sibling topics on the same danger: electrocution.
 
RE: Power Line Misunderstandings  
by NI0C on July 16, 2008 Mail this to a friend!
On July 6, I had an encounter with the HV line that crosses the back of my property when I was putting up my Force 12 Sigma 40XK vertical dipole after a manual band change. My life was saved by the fiberglass insulator between the top and bottom halves of the antenna. Fortunately, I had removed the hairpin match coil from the antenna when changing bands.

To say I was lucky is an understatement I was not physically hurt at all; however I have had nightmares since the incident.

The top T bar that touched the wire had a 3/8" hole melted in it, the SO-239 on the balun assembly became unsoldered, and my MFJ remote antenna relay blew up in an explosion that sounded like a shotgun blast.

I reported this incident on the F12 reflector, and received a very sobering e-mail from a ham who survived a HV accident in his work at a utility company-- he suffered horrible injuries.

HV is nothing to take chances with.

73,
Chuck NI0C




 
RE: Power Line Misunderstandings  
by K5END on July 16, 2008 Mail this to a friend!
"Too bad the ham and his son who got electrocuted recently while putting up an antenna did not have a chance to read your article. They could have avoided "death." "

Actually, I did write some brutally frank opinions on the topic very recently when another eham poster discussed locating his antenna near power lines. In fact, several eham members expressed concern.

I wish it had occurred to me to write this up as an article at the time. (But that is no guarantee the parties would have seen the article.) It was after I read the terribly sad news that I felt motivated to write it.

This issue is something we should all be aware of. Even armed with the knowledge, human nature is such that we will sometimes still take risks, or somehow rationalize that it only happens to other people.

The unforgiving nature of this hazard requires a very frank, personal or even sensational presentation.

People learn in at least three ways.
1. Receiving information.
2. Observing others.
3. Trying it.

At this point the readers of this news are armed with #1 and, unfortunately, #2 as well.

Don't employ method #3.
 
RE: Power Line Misunderstandings  
by K0BG on July 16, 2008 Mail this to a friend!
While we (it was I, actually) are bridging the gap (couldn't resist the pun in hopes of putting some levity on the subject) between power lines and lightning, they are related in that they both arc. But is isn't things that arc per se, it is watching out for all of those things that can "getcha!". The key word here should be one of safety first.

In times past, QST (and CQ for that matter) has always stated the obvious with respect to safety. However, from a personal perspective, that outlook has diminished of late. I regularly see articles violating all manner of safe operating practices, without so much as a second thought to it. Let me give you an example, albeit one of my pet peeves; the lowly mag mount antenna.

Some time back, I mentioned in a thread that there had been two reported cases, and possibly a third, where someone was struck and killed by a mag mounted antenna. One luckless amateur actually responded with a statement to the effect that that was pretty fair odds.

If anything comes out of the loss suffered by the families of the two men in question, perhaps it will be that the editors of the respective amateur radio magazines will take a renewed look at the importance of stressing safety first.

Alan, KBG
www.k0bg.com
 
RE: Power Line Misunderstandings  
by N6AJR on July 16, 2008 Mail this to a friend!
One of my miriad of jobs was as a lineman for a cable TV company in the San Jose area of Ca. I had a super lineman to instruct me in some of the finer points, of using climbing gear ( hooks and a belt) and we were very aware of the power in the overheads.

a second mention is the back feed problem. that is so true . if you think about it, the same transformer that drops the 7 to 10 KV power down to 110/220 v house power works just fine in the reverse also. so to use the "gorillia power" trick you just plug your generator in to either leg of the house wireing, ( like an extension cord with males on both end)

the trick here is to throw the breakers ( the main power breakers ) at the panel where it comes in the house. this removes the power from back feeding the powerlines. be sure to remove the generator power before throwning the brakers when power comes back on.

Also when you throw the breakers to isolate the generator from the power lines, put a note on the breakers so some one does not throw them with out you knowing, and you can lock them open on some panels.

better yet is to just run a couple of power cords in the house and hook up the tv, fridge and a couple of lights to the generator that way, and be sure to run the generator where the fumes won't kill you, like in a closed garage.
 
RE: Power Line Misunderstandings  
by AI4NS on July 16, 2008 Mail this to a friend!
"better yet is to just run a couple of power cords in the house and hook up the tv, fridge and a couple of lights to the generator that way, and be sure to run the generator where the fumes won't kill you, like in a closed garage."

The best solution is to have your main service panel modified to allow a connection with a generator. I have a whole house generator that automatically switches commercial power off, etc. I also have a plug on the side of the house for a portable generator. It feeds a breaker in the service panel that can only be turned on when the main breaker is shut off. There is a mechanical interlock that allows only one of the breakers to be engaged at one time. It cost me a few hundred dollars, but the piece of mind and safety is well worth it.

Mike
AI4NS
 
RE: Power Line Misunderstandings  
by K0EWS on July 16, 2008 Mail this to a friend!
Great article! One of the best I've seen on Eham for a while. Great subject; timely and informative. Thanks for sharing it!
 
RE: Power Line Misunderstandings  
by AC7ZL on July 16, 2008 Mail this to a friend!
Some additional comments about power lines and the energy that they carry:

When I was kid back in Michigan, we suffered a pretty nasty ice storm one winter. The ice glazed everything to such an extreme that large tree limbs snapped off, power poles toppled, and power lines broke under their own weight. Lots of people lost power. We didn't have electricity for a week---serious business in the dead of winter.

There were numerous warnings on TV and on the radio. Here are a few things that I observed:

a) A power line landed on a chain-link fence that separated our backyard from our neighbors. That line remained energized for a long time, and in the dark, one could see the blue glow of corona discharges from the fence. You could hear it buzz and sizzle.

b) A wooden fence in an adjacent yard came into contact with one of those wires, and simply burst into flame. Interestingly, it burned from the bottom (where the posts went into the ground) on up.

c) I was lying in bed in the dark one night and had just closed my eyes when I heard a loud, deep rumble. The room seemed to light up with daylight. I jumped out of bed, peered through the window into the darkness, but saw nothing. I went back to bed. I had just closed my eyes when I heard a rumble and the room filled with light. I jumped out of bed, and again, saw nothing. This happened several more times until I committed to standing at the window until that "something" happened again. As near as I can tell, an intermittent short somewhere was causing huge currents in some lines across the street, which begin to thrash. They would contact each other, and a blue fireball the size of car would race up and down the wire.

d) The following spring, my brother and I poked around in the dirt beneath one of the utility poles that had lost a wire. We found "tentacles" of dirty glass---literally molten and fused sand, where downed lines had contacted the earth.

Pete
AC7ZL
 
Power Line Misunderstandings  
by KC0TAS on July 16, 2008 Mail this to a friend!
In the Army (Signal Corps) we were always taught twice the height away from any overhead line (powr or otherwise). Try and to the same in my QTH Installaiton. Very lucky that the P{ower feed comes in form neighbors back yard on an angle to the back of my house. The other line is a cable feed on the other side from across the main road. All Antenna are on the roof or over it. Just have to make sure that I disconnect when at work or when there is a forecast for a Thundersotrm. Kansas -- home of Thunder boomers and high winds!!

All of the remarks are good to follow.

Work for the state as a dispatcher. Last spring the main tower outside the dispatch center took a direct stike. I was standing inside the building about 15 feet from the base of the tower!! Played havoc with our systems. Took 24 hours to get everything back up.

That taught me quicker than any other5 class I could have taken ro given!!

Joe
NJ0E
 
RE: Power Line Misunderstandings  
by K5END on July 16, 2008 Mail this to a friend!
Regarding back feed from home generators to the power lines, I can affirm this is indeed a big, big problem presented unwittingly by consumers.

There are enough problems in removing trees and fractionalized houses, etc. etc. from the power distribution facility after an event such as a hurricane. This back feed just adds to the problem and presents a significant delay in power restoration for the community.

Those who make this error are likely to get their meter pulled and will be of the last to get service restored, or so I have heard.

Yes, running a generator without disconnection from the service line is a bad thing to do and can lead to injury or fatality.

If nothing else, what consumers do not realize is that they are providing free power to the neighborhood when they back feed the lines. That will overload their generator and use up their fuel that much faster.
 
Brutal Facts  
by KA4KOE on July 16, 2008 Mail this to a friend!
The difference between gettin' kilt by house AC at 240/120V, vs the 14.4/7.2 KV typically running overhead is very simple......open vs. closed casket funeral.

Charbroiled baby.

FEELEEP
 
Power Line Misunderstandings  
by W8KQE on July 16, 2008 Mail this to a friend!
Phenomenal article! We need more like this regarding power lines.

Just curious. What about the 3 wire (2 insulated black, 1 exposed aluminum?) twisted feeder line that goes from the power pole to your house? Is that 120VAC or 220? That particular line seems to be well insulated, and I have been using one of those 15 foot fiberglass/plastic branch trimmer poles to trim nearby smaller tree branches that are just mere feet away from the feeder line. If a branch, or my fiberglass/plastic pole should come in contact with this feeder line, am I safe, because it is seemingly insulated? Or is it just the super high voltage power lines that run from pole to pole that we should be mainly concerned about?

Thanks in advance!

73, George
W8KQE
 
RE: Power Line Misunderstandings  
by WC4V on July 16, 2008 Mail this to a friend!
"One other problem is that if a high voltage line is in contact with the ground, because the soil (or pavement) is only a moderately good conductor, there is a voltage gradient radiating out from the point of contact that can be lethal at quite a distance."

This is what is called step-potential. If you find yourself in this situation, it is best to keep your feet together, and hop to safety. The plan is to keep both feet within the same "potential zone."

"if you think about it, the same transformer that drops the 7 to 10 KV power down to 110/220 v house power works just fine in the reverse also."

Yup that is right. During a major ice storm in Lexington Kentucky, back in 2003, a utility lineman met an unfortunate fate. While all the circuits were pulled in the substations, one must always presume that downed power lines are "hot" One customer had taken an extension cord, with to male ends, from his generator to a wall outlet. The main breaker was not in the off position and his meter was still in the base. When the line was in the back yard clearing a tree off the downed line, he picked up the line, taking 7.2 kv through him. Just remember, always consider power lines live!

WC4V
Steve
 
RE: Brutal Facts  
by KA4KOE on July 16, 2008 Mail this to a friend!
Another thing to consider....the voltages encountered render most common insulators conductors. Its a wonder that Ben Franklin wasn't killed in his kite experiment (if in fact it happened), even though the kite line at the end was silk.

Nasty stuff. Zeus' Thunderbolts are not to be trifled with.

PAN
 
RE: Power Line Misunderstandings  
by KA4KOE on July 16, 2008 Mail this to a friend!
The two black conductors are phase a and phase b. The bare conductor they are wrapped around is the neutral or a traveler which all three are supported by. The neutral can be aluminum. Also, 220V is a misnomer. Its 240V. The typical house drop is 120/240V, 1 phase, 3 wire.

 
RE: Power Line Misunderstandings  
by KA4KOE on July 16, 2008 Mail this to a friend!
"That particular line seems to be well insulated, and I have been using one of those 15 foot fiberglass/plastic branch trimmer poles to trim nearby smaller tree branches that are just mere feet away from the feeder line."

NEVER NEVER NEVER NEVER assume the insulation will protect you if you come into contact with it. Friend, stop taking chances.
 
RE: Power Line Misunderstandings  
by KA9HXD on July 16, 2008 Mail this to a friend!
The line to which you are referring is the "triplex" power feed to your house. The two insulated lines are 240 volts as measured between them or 120 volts as measured to the uninsulated grounded "neutral" line (this line is grounded - bonded at the pole and at the house service panel). It is somewhat difficult to receive a shock from this line, but not impossible. The insulation on the insulated conductors can crack with age making it possible to come in contact with. These lines are only protected by the power company distribution transformer primary side fuse. The instantaneous fault current available on these lines can approach 10kAmps or more. So, they're nothing to mess with. The power company distribution lines typically located at or near the top of power poles run in the range of 2.4kv to 25kv and are the ones that sometimes come down in storms and can come in contact accidentally with antenna installations. These lines are usually uninsulated and are very bad news.
 
RE: after 2 duds we have an informative article  
by W4LGH on July 16, 2008 Mail this to a friend!
KC8BYF asks..."There are 3 things I have heard about lightning. I want to know if they are true. Perhaps, someone here knows or has witnessed these things first hand.
1) I have heard that before lightning strikes, the ground, in the area of the preeminent strike, puts out a type of static "feeler". In a sense, the charge between the sky and earth searches out the best spot for the strike before it happens.
-----
This is very true! Its referred to as a stringer!

2) I have also heard that lightning mostly travels from the ground up?
-----
False..#3 is the correct answer!

3) Lastly, I have heard that lightning goes both directions, from the clouds downward as well as the ground upward, and meets in the middle...?
Yes..the stringers go up, and there are stringers coming down from the clouds. If they meet, you get a lightning strike. The strike is traveling in BOTH directions at the speed of light, hence it is traveling at twice the speed of light. As the old saying goes.."faster than Lightning!"

Maybe someone knows of some good websites to read reliable material on lightning, lightning safety and possibly some prevention tips other than "stay indoors".

There are lots of great articles about lighting out on the web. Just Goggle it!

73 de W4LGH - Alan
http://www.w4lgh.com

 
RE: after 2 duds we have an informative article  
by K5END on July 16, 2008 Mail this to a friend!
quote, "The strike is traveling in BOTH directions at the speed of light, hence it is traveling at twice the speed of light."

Wellll...we'd have to look carefully at the physics. The plasma wave does indeed travel fast, but not "at" the speed of light. (Of course the light radiated from the lightning plasma does travel at the speed of light, by definition.)

The real gotcha in physics is that two wavefronts traveling toward each other at the speed of light would not imply that they congress at twice the speed of light.

I know that sounds wrong according to intuition, but that is, in part, the theory of special relativity. Break it down logically. Why would light travel at something other than the speed of light? This is part of what perplexed Einstein and therefore led him to the fruits of his genius and contributions to physics.

There isn't really a way to prove or debate this point further without going to the math and rigorously detailing it, as Einstein did, so for me this won't be something I'll debate here.

Even when Einstein won the Nobel Prize for the Photoelectric effect, the scientific community was still not yet wholly convinced of his theories of special and general relativity. Therefore I hold little hope of convincing anyone of the same with merely an internet post.


 
RE: Power Line Misunderstandings  
by K5END on July 16, 2008 Mail this to a friend!
"If anything comes out of the loss... perhaps it will be that the editors of the respective amateur radio magazines will take a renewed look at the importance of stressing safety first."

Alan, I'm pleased to hear someone say that.

Amateur radio isn't meant to be an "extreme sport" with high risk for injury.

The inherent dangers can be made safe with a reasonable effort. I believe this.

PS. Thanks for what you've written concerning mobile on the Ridgeline. I've promised myself that when the weather cools down a bit I'll get rigged up for HF mobile. It's just way too hot and humid here right now for me to be working outside on a car. Heatstroke is another safety issue!!
 
RE: Power Line Misunderstandings  
by N6AJR on July 16, 2008 Mail this to a friend!
so here is a speed of light question

if you turn on a flashlight the light comes out at the speed of light, so if you hold it out the window facing foward while traveling 60 MPH in a car is it actually going the speed of light PLUS the speed of the car..

inquiring minds want to know :)
 
RE: Power Line Misunderstandings  
by K0JEG on July 17, 2008 Mail this to a friend!
No, because nothing can travel faster than the speed of light, as theorized by Einstein.

http://en.wikipedia.org/wiki/Special_theory_of_relativity#Causality_and_prohibition_of_motion_faster_than_light

Interestingly (at least to me), it is possible for light to travel slower than 186,000MPS, as it does when passing through matter such as air.

Strange stuff.
 
RE: Power Line Misunderstandings  
by WA1KWA on July 17, 2008 Mail this to a friend!
Great post. Safety cannot be over-emphasized.

Maybe someone more eloquent & knowledgable than myself can develop this into a series. I would go so far as to suggest this be a series in QST to reach the widest audience. They have issues devoted to various subjects, such as antennas & vintage radios; an issue devoted to safety should be considered.

Lightning was previously mentioned as a subject for a future safety article. I would like to suggest a couple more:

Equipment Safety. Liner amplifiers have components operating in the kilovolt range, with subsiquent safety issues.

Mobile Safety. Installation and operating. Poor installations can result in injury or worse in a collision. Poor installations can cause a fire. Poor installations can cause a collission, due to the driver being distracted.

A previous poster said trees were poor conductors. Reminded me of an incident when I was a teenage ham. A friend was swimming in a large lake. There was a lightning storm on the horizion. I suggested he get out, his answer was that water was a poor conductor.

Trees & water are indeed poor conductors. But they are still conductors.

Be safe.

73,
Colin WA1KWA
 
RE: Power Line Misunderstandings  
by W4LGH on July 17, 2008 Mail this to a friend!
Ok...good debate going on here....

K5END said.."I know that sounds wrong according to intuition, but that is, in part, the theory of special relativity. Break it down logically. Why would light travel at something other than the speed of light? This is part of what perplexed Einstein and therefore led him to the fruits of his genius and contributions to physics."
----------------
To explain what I said about twice the speed of light, was, in simple terms if you have 2 objects traveling towards each other at 100mph, the difference between them is 200mph, or twice their speed. Now if lightning originates from the ground as a stringer, and then the cloud, and they travel at each other, the difference between them would be twice the speed of light.
---------------
N6AJR asks..."if you turn on a flashlight the light comes out at the speed of light, so if you hold it out the window facing foward while traveling 60 MPH in a car is it actually going the speed of light PLUS the speed of the car.."
-
N3KQX answers..."No, because nothing can travel faster than the speed of light, as theorized by Einstein."
---------------
I personally would say "Yes" the speed would be increased by 60mph. When Einstein did his work, it was good. But there is no logical reason why the speed of light would be the fastest anything can travel. In the gran scheme of things, what would 60mph be, added to 186,000 MPS? Hardly measurable. We know that different wavelengths of light travel at slightly different speeds. We use this data to measure whether stars are traveling to us, or away from us.
Everything in life is relative, so using the speed of sound, we know when we travel faster than sound, we leave the sound behind us, so why would light be the same? If we were able to travel faster than light, we would have to travel in total darkness, as far as our human senses are concerned, as we would be leaving the light behind us, and the light coming at us, would be compressed into higher wavelengths, above our visual spectrum.

Saying the NOTHING can travel faster than the speed of light is the same as saying there is a finite number out that that once reached, there is nothing higher, or that there is an end to the universe, a line that if reached one would venture into complete NOTHING.

Einstein certainly was a very smart man, and advanced our knowledge a great deal, but I can not buy into the idea that NOTHING can travel faster. Maybe he meant that Light can not travel fast than the speed of light?

Its a deep subject, a certainly opens up a BIG can of worms. But thats my 2 cents worth.

73 de W4LGH - Alan
http://www.w4lgh.com



 
RE: Power Line Misunderstandings  
by K5END on July 17, 2008 Mail this to a friend!
quote, "But there is no logical reason why the speed of light would be the fastest anything can travel."


Sure. Go with that.

If you can prove this you'll be a good candidate for a Nobel Prize in physics and will join the ranks of Isaac Newton, Albert Einstein, Bohr, Pauli, Dirac, La Place, Fourier, Heisenberg, etc.

There are some discussions regarding electron spin requirements, and you may wish to look up Bell's Theorem. That ought to get you started.

Also, there is much to learn about gravitational theory, so you may have some leads through that.

You won't get far until you've mastered Tensor analysis, vector calculus and can solve a differential equation or two, so you may wish to back up a bit and start with those.

Keep working on it. Best of luck. :-)
 
RE: Power Line Misunderstandings  
by K5END on July 17, 2008 Mail this to a friend!
Colin,

I think you have an excellent idea. A monthly column/article in QST on safety would be great.

If QST receives enough letters requesting such a column it just might happen.

I'll write my letter and submit my request (based on your suggestion) to them today.

73
Larry
 
Power Line Misunderstandings  
by KN4LF on July 17, 2008 Mail this to a friend!
My Very Close Encounters With Florida Lightning Bolts

http://www.kn4lf.com/kn4lf1.htm

73 & God Bless,
Thomas F. Giella, KN4LF
Lakeland, FL, USA
 
RE: Power Line Misunderstandings  
by W9PMZ on July 17, 2008 Mail this to a friend!
"Yup that is right. During a major ice storm in Lexington Kentucky, back in 2003, a utility lineman met an unfortunate fate. While all the circuits were pulled in the substations, one must always presume that downed power lines are "hot" One customer had taken an extension cord, with to male ends, from his generator to a wall outlet. The main breaker was not in the off position and his meter was still in the base. When the line was in the back yard clearing a tree off the downed line, he picked up the line, taking 7.2 kv through him. Just remember, always consider power lines live"

OK, you back feed the power panel, so everyone else on the branch that feeds the transformer will also have AC? Wouldn't the current required to back feed everyone else on the branch take the generator down?

Just wondering....

73,

Carl - W9PMZ
 
RE: Power Line Misunderstandings  
by KD2BD on July 17, 2008 Mail this to a friend!
N3KQX wrote:

> Interestingly (at least to me), it is possible for light to travel slower
> than 186,000MPS, as it does when passing through matter such as air.
>
> Strange stuff.

True, but it IS traveling the speed of light *for that medium*.

What I find fascinating is that scientists have discovered that there isn't enough voltage potential between a thunderstorm cloud and the Earth to produce a lightning strike. Yet, there's no question that they occur.

It appears that lightning bolts receive the extra energy they need to form a strike through background cosmic radiation. The radiation reaches the levels required to form the conductive path in bursts, and arrives at Earth from various directions.

(See http://www.pbs.org/wgbh/nova/sciencenow/3214/02.html)

If you've ever watched NASA-TV during a Space Shuttle mission, NASA will often point Shuttle cameras toward active thunderstorms over the dark side of the Earth.

It soon becomes obvious from this video that lightning strikes aren't random acts of nature. They occur in bursts, even over large areas, much like the waves of cosmic rays from outer space that help produce them.

The lesson in all this is that just because you've just experienced a nearby lightning strike doesn't mean you're out of the woods for the next few minutes.

Thunderstorms don't need time to "recharge".


73, de John, KD2BD
http://kd2bd.ham.org/
 
RE: Power Line Misunderstandings  
by K5END on July 17, 2008 Mail this to a friend!
quote, "OK, you back feed the power panel, so everyone else on the branch that feeds the transformer will also have AC? Wouldn't the current required to back feed everyone else on the branch take the generator down? "

If the load exceeds the generator capacity, yes, something like that would happen. Most likely the voltage would drop. The generator may overheat or self protect.

The load impedance as seen "looking" toward the utility plus the local impedance and the internal impedance of the generator would dictate what happens to the voltage and current.

Note, there are some pretty big standby generators out there among the population.

I saw a lineman safety poster that says, "if it isn't grounded, it isn't dead." I suppose that means the procedure is to ground all the conductors presumed to be off line before doing any work.

Again, backfeeding the utility could have many adverse effects. It might even result in getting the offender's meter, thus service, removed with replacement of the meter after an outage as a last of the last priorities. I don't know.
 
RE: Power Line Misunderstandings  
by WA1KWA on July 17, 2008 Mail this to a friend!
Larry,

When I get home I'll email ARRL & add my voice to this.

73,

Colin WA1KWA
 
RE: Power Line Misunderstandings  
by KE7FD on July 17, 2008 Mail this to a friend!
Great information and the kind of in-your-face reminder. "No do-overs" is right.

Thanks for the article.

Glen - KE7FD
 
RE: Power Line Misunderstandings  
by K5END on July 17, 2008 Mail this to a friend!
quote, "What I find fascinating is that scientists have discovered that there isn't enough voltage potential between a thunderstorm cloud and the Earth to produce a lightning strike"


One thought on this problem, based on the premise that cloud-cloud lightning is more common than cloud-ground lightning, is that the Earth's surface may sometimes be merely the medium between two equalizing regions of clouds.

Interestingly, nuclear weapon tests normally have significant lightning activity surrounding the bomb cloud as it expands, as is the case for the rising plume from a volcanic eruption.

I concur with your use of the word "fascinating."

 
Power Line Misunderstandings  
by K9EEE on July 17, 2008 Mail this to a friend!
We had a situation a week or two ago in one of our Twin Cities (Minnesota) suburbs with a new pedestrian / bike path bridge that opened.

Several people complained to the City about problems, most notably the bicyclist who described it as feeling like he had 'bees in his shorts'.

They decided that the steel bridge was inductively coupled with the high voltage power lines that passed over it. Though there was no contact with the wires, the bridge was closed until more effective grounding could be installed to dissapate the charge.

Not something I would have ever assumed.

Phil
K9EEE
 
RE: Power Line Misunderstandings  
by FORMER_W7LV on July 17, 2008 Mail this to a friend!
>>> and can solve a differential equation or two

Oooh, yuck. I can remember shlepping across campus twice weekly for an 0800 torture session called, "Ordinary Differential Equations."

One of MANY bad things to remember from 1967-1973...
 
RE: Power Line Misunderstandings  
by KA4KOE on July 17, 2008 Mail this to a friend!
Its really rude when one clicks on a link, and a loud WAV file blasts them out of a chair.

PAN
 
RE: Power Line Misunderstandings  
by W1RKW on July 17, 2008 Mail this to a friend!
If you're back feeding power using a generator you're nuts in my opinion. First, you're in violation of the NEC. Second, for the few hundred or so dollars you could spend on a transfer switch you could save the life of a line worker if you become absent minded or have someone flip a breaker unknowingly. That's very irresponsible as far as I'm concerned.
 
RE: Power Line Misunderstandings  
by W9PMZ on July 17, 2008 Mail this to a friend!
Well I agree that a circuit shouldn't be back feed. I was just trying to understand what would happen if you did.

Since most generators that seem to be sold are in the 5KW range and since transformers are bidirectional devices, If someone fed his panel and did not disconnect it the mains I can't see how in an urban or city enviroment how the generator wouldn't trip its own breaker. The load presented to the generator to power the grid would be enoromous. We all don't go to the panel to trip the mains until power is resoted.

The only thing that I can think is if you feed you panel and didn't disconnect the mains and you had a break in your line to the transformer, especially common in a rural area, that this would be a major issue.

73,

Carl - W9PMZ
 
RE: Power Line Misunderstandings  
by K5END on July 17, 2008 Mail this to a friend!
quote, "The only thing that I can think is if you feed you panel and didn't disconnect the mains and you had a break in your line to the transformer, especially common in a rural area, that this would be a major issue. "

If I understand the scenario you're posing, a customer is disconnected from the utility because of open fuses or broken lines severed somewhere between his meter and the rest of the distribution, yet runs his generator without pulling his meter or opening his mains(?)

Then, yes that would be perhaps one of the most dangerous possibilities of all.

His generator would not be loaded down by his neighborhood, but the lines from his house would still be live from his own generator. That would present the highest voltage on the open lines.

That is a good example of how an unsuspecting utility worker, or kids playing, or anyone, could be could be exposed to high voltage on assumed dead lines.

Thanks for posting that example.

 
RE: Power Line Misunderstandings  
by W9PMZ on July 17, 2008 Mail this to a friend!
K5END, thanks for the information, but your not really in my mind answering the question that I am curious about.

Assume you live on a city block where 4 or 5 houses connect to the same transformer (I don't work for a utility so I don't know the proper configuration) and the break is upstream from that transformer.

The power goes out. The 5 houses are all dark. House number 3 goes grabs his 5KW generator and connects it to the panel without disconnecting the mains.

As I understand electricity, not only will his panel be energized, but also houses 1, 2, 4 and 5. How can a typical portable generator energize the circuit without tripping?

73,

Carl - W9PMZ
 
RE: Power Line Misunderstandings  
by G3RZP on July 18, 2008 Mail this to a friend!
The potential along the ground from a lightning strike ia the usual thing that kills cattle. Cows are very susceptible to quite small voltages between front and back legs, and, of course, are frequently in very good electrical contact with ground. In the UK, there are special requirements for wiring milking parlours because of this.
 
RE: Power Line Misunderstandings  
by W4LGH on July 18, 2008 Mail this to a friend!
W9PMZ asks..."As I understand electricity, not only will his panel be energized, but also houses 1, 2, 4 and 5. How can a typical portable generator energize the circuit without tripping?"

That has always been a good question, and the logical answer would be, YES, it would LOAD the generator down and would either trip out YOUR main circuit breaker, or choke out the generator. However a 5K generator will only make about 25amps and my main are 200amps. This is why you disconnect your mains before starting your generator. Another reason is, that it is possible to energize the main trunk lines thats service techs could be working on. The same transformers that drop the voltage coming into your house, will now step that voltage back up, and it could KILL the tech working on, what he thought was a DEAD line.

73 de W4LGH - Alan
http://www.w4lgh.com


 
RE: Power Line Misunderstandings  
by K5END on July 18, 2008 Mail this to a friend!
"As I understand electricity, not only will his panel be energized, but also houses 1, 2, 4 and 5. How can a typical portable generator energize the circuit without tripping?"

I think I posted the answer a day or two ago, but it just depends on the parameters. If the additional load from his neighbors exceeds the generator's "ability," then the voltage will decrease, it will overheat, self protect, open a breaker and/or use a lot more fuel.

The 5 KW size you propose will barely run one house with central HVAC or air conditioner sized for a single house where I live, so it wouldn't handle more than one house in the summertime, at least not for long.

After a hurricane here we used a heavy duty inverter on our vehicle for a day or two. I think it was 2500 W. It was enough to power the microwave oven and TV, a few lights and keep the computer live on the internet...but not all at the same time! We had to pop the popcorn before sitting down. It made it seem more like going to the real movies, hi hi.
 
RE: Power Line Misunderstandings  
by K5END on July 18, 2008 Mail this to a friend!
OIC... your question was about tripping the main breaker and not a breaker on the generator?

Yep. Someone answered that one in the previous post.
 
RE: Power Line Misunderstandings  
by G3RZP on July 18, 2008 Mail this to a friend!
It has never ever occurred to me that when one uses an emergency generator, BEFORE connecting it, one would NOT isolate the incoming feed from the power lines. Is it because I'm an engineer? It's just so obviously plumb crazy not to open the breaskers, pull fuses or whatever to isolate those lines.
 
Power Line Misunderstandings  
by KU4UV on July 18, 2008 Mail this to a friend!
I have a newscast video of a power line safety demonstration that was held at one of the local hamfests I attended back in August of 1999. I have been trying to figure out how to upload it to Youtube, but I'm not having much luck. I don't have a video capture device, so I may have to wait. If I can somehow get it posted this weekend, I'll let everyone know. Thanks!

KU4UV
 
RE: Power Line Misunderstandings  
by K5END on July 18, 2008 Mail this to a friend!
"It has never ever occurred to me that when one uses an emergency generator, BEFORE connecting it, one would NOT isolate the incoming feed from the power lines. Is it because I'm an engineer? It's just so obviously plumb crazy not to open the breaskers, pull fuses or whatever to isolate those lines."

It's far too easy to underestimate the ignorance of electricity in the general public. The average Jack and Jill wouldn't know a Hertz from a Watt.

What seems obvious and intuitive to one informed is quantum mechanical dark matter witch doctor pure magic to another.

Listen to news reporters sometime. They talk about "Volts surging* through a victim," or "Watts of energy**," and so on. Don't get me started/// too late. :-)

Another peeve is "rate of speed." Speed IS a rate. It's like saying Tuna Fish. To a physicist or mathematician, "rate of speed" means "acceleration."


For the casual forum visitors...

* Amperes flow, not volts

** A Watt is a unit of power. The Joule is the SI unit of energy. Power and energy are not the same dimension.
 
RE: Power Line Misunderstandings  
by WA1RNE on July 18, 2008 Mail this to a friend!

"I have a newscast video of a power line safety demonstration that was held at one of the local hamfests I attended back in August of 1999. I have been trying to figure out how to upload it to Youtube, but I'm not having much luck."


>>> I just posted this concerning the recent article on eHam titled "Two Dead in Electrocution Accident" and believe it's worth posting here as well. How coincidental that K5END posted his article after this incident:


"As part of a Demonstrated Skills element (call it Element 1, replacing CW) that verifies an applicants ability to set up and diagnose typical amateur equipment and antenna installations, an applicant should be able to identify what is considered safe installation practices for antennas and feeders near power lines. A couple of PowerPoint slides could be used with photos of real situations - good and bad.

As they say, a picture is worth a thousand words, but in this case, they could save lives."


I used to work as a Sales Engineer for a company that sold test instrumentation to the electric utilities. I have performed many demo's inside HV substations, testing high voltage breakers and relaying, obviously de-energized, but rated for 230-345kV transmission voltages with the power isolated but still nearby. The safety factors and practices involved for working near this amount of power are incredible and they need to be. When you hear the fizzle of corona and think about some of the poor souls who were involved in utility equipment failures or accidents and the horrendous injuries they sustained or death, you develop a respect for power quickly.

Obviously, most hams won't get this type of training but some well thought out training slides can get the point across. Maybe someone knows of a utility training video. I recall a good program on the History Channel about linemen.

There was another program on cable that told the story of a young lineman who worked for PSE&G (Public Service Electric and Gas, of New Jersey) who was severely injured in a power line accident - he lost both arms working on a 38kV line. (the voltage may be wrong)


...WA1RNE


....WA1RNE
 
RE: Power Line Misunderstandings  
by KD8EUR on July 18, 2008 Mail this to a friend!
First off this is a great post, with a ton of good info. (And nice to see a topic remain civil too)

Found this video on youtube http://www.youtube.com/watch?v=xy7MWzctTm0

Worth the watch. But it would be neat if a power compnay with the ARRL would make a video with hams being the focus. I think nothing would drive the point home like seeing a beam antenna swing into a high voltage line. Or 2 meter vertical get within a few feet.

73
KD8EUR
 
RE: Power Line Misunderstandings  
by NI0C on July 18, 2008 Mail this to a friend!
K5END wrote:
"For the casual forum visitors...

* Amperes flow, not volts"

Actually, it is electrical charge that flows. Charge is measured in Coulombs, and the Ampere is our unit of electric current, which is the time rate of charge flow (Coulombs per second).

Saying that "Amperes flow" is to be off by a time derivative (as in your example of "rate of speed").

73,
Chuck NI0C
 
RE: Power Line Misunderstandings  
by G3RZP on July 18, 2008 Mail this to a friend!
And Watts are Joules/sec.

Normally, one would figure breakdown at 30kV/inch. Where HV is concerned, I like the idea of a separation between me and it of a minimum of 12 inches plus one inch for every kV when I'm workin on it. And preferably with a good thick insulator in the way, too.

At college, we would routinely do experiments where we had leads with oncovered spade ends to connect up the experiments, and then have up to 415 volts of 3 phase or 220 volts DC on these open terminals. But that was 40 years ago. I guess these days, it just wouldn't be allowed - but you certainly learnt to keep you fingers out!

I guess you're right and your average joe doesn't know enough to know he doesn't know. Pope got it right in 1711:

A little learning is a dangerous thing
 
RE: Power Line Misunderstandings  
by K5END on July 18, 2008 Mail this to a friend!
quote, "Actually, it is electrical charge that flows. Charge is measured in Coulombs, and the Ampere is our unit of electric current, which is the time rate of charge flow (Coulombs per second). Saying that "Amperes flow" is to be off by a time derivative (as in your example of "rate of speed")."

Thanks, Chuck. That is an astute observation.

I believe you are 100% correct for case of the noun, as in "Amperes of flow" but perhaps not for the case of the verb, as in, "Amperes flow." And that would hold fast for the "rate of speed" example, where both "rate" and "speed" are nouns.

Therefore this may be a linguistic dilemma.

Consider that:
1. The Ampere is the SI unit of current: 1 Coulomb per second. You know this.
2. Current flows. It's what current does.

If we "Edisonize" the analysis, "gallons per second of flow" would be tantamount to "rate of speed." I'll concede that easily.

But to say "gallons per second flow (verb)" would be a correct statement. I think.

Coulombs may or may not flow, but Amperes have no choice but to flow, (verb) by definition.

The argument does not apply to examples such as, it is incorrect to say, "degrees Kelvin." I think you see that. When I hear someone say, "degrees Kelvin" it helps me catalog him/her neatly, and without doubt. :-)

Disclaimer: It's been a very long day with miles of hot driving, so I may not be firing on all neurons at this point. I could be wrong. If I AM mistaken, I want to be the first to know! I'll check with some family member physicists to get their perspective and get back on this later.

I would very much like to hear your counterpoint on this.

Thanks again,
Larry
 
RE: Power Line Misunderstandings  
by NI0C on July 18, 2008 Mail this to a friend!
Larry,

I want to preface this by saying I don't want my quibbling to distract in any way from the important message of your article. After all, I'm one who was careless enough to almost get killed by HV on July 6, as reported above!

All I'm saying is that a flow rate (such as an ampere of current, or gallons per second) does not flow-- rather, it describes the flow of something (a quantity of electrons, or some fluid).

Thank you for your article. It's great to be alive!

73,
Chuck NI0C
 
RE: Power Line Misunderstandings  
by W4LGH on July 18, 2008 Mail this to a friend!
Getting pretty deep here, with coulombs , joules, amperes and watts.

So people will know..
A Joule is the amount of energy dispensed and does not always equate to electricity. It can be kinetic energy as well.
1 joule = 1 newton metre = 1 watt second or he amount of energy released if you dropped an apple from 1 meter.

Coulombs originally was SI base electrical unit.
1 coulomb is the amount of electric charge transported by a current of 1 amp in 1 second.
In 1960 Coulombs were replaced with Amperes as the SI base.

And Watts, well watts is watts. 1 volt @ 1 amp is 1 watt.

1 volt @ 1000 amps is 1000watts, but 1000 volts @ 1 amp is also 1000 watts of current. Exactly the same amount of current. However you can stand in salt water and grab a wire with 1 volt @ 1000 amps, and be safe, however don't try that with 1000 volts @ 1 amp, the same amount of current. I promise you, you will not be safe, and more than likely..DEAD!

So based on the examples above which one has the most Joules? 1v @ 1000amps or 1000v @ 1 amp? We already know the current is the same...1000watts.

73 de W4LGH - Alan
http://www.w4lgh.com

 
RE: Power Line Misunderstandings  
by K5END on July 18, 2008 Mail this to a friend!
"How coincidental that K5END posted his article after this incident"

As I said, it was not a coincidence.

When I read the news (more to the point, when I read the forum comments on the news) I wrote the article the same evening and submitted it to eham.
 
RE: Power Line Misunderstandings  
by K5END on July 18, 2008 Mail this to a friend!
quote, "So people will know..
A Joule is the amount of energy dispensed..."

So what is 1 Joule/Coulomb?

 
RE: Power Line Misunderstandings  
by K5END on July 18, 2008 Mail this to a friend!
Hi, Chuck

Thanks for your comments.

"All I'm saying is that a flow rate (such as an ampere of current, or gallons per second)..."

That point is where we may differ in our definitions.

I'd always thought that the Ampere is defined as current, and not the rate. You may be right. Would be interesting to know.

<...digging out old mildewed, yellowed-paper college physics textbooks...>

:-)

73
Larry







 
Power Line Misunderstandings  
by KU4UV on July 19, 2008 Mail this to a friend!
I have now posted a video on Youtube of an electrical power line safety demonstration that was held at one of the local hamfests here in town several years ago. This video was taken on 8-16-1999, and was part of the WLEX-TV 18 6:00PM newscast here in Lexington, Kentucky. My twin brother Patrick, KR4GT, is the guy you see in the cutaway shot rubbing his chin, and I am standing directly to his right. The reporter who shot this video actually interviewed my brother to get his thoughts on the demonstration, but I guess they decided not to use the clip It's amazing how fast time goes by, as this video was shot almost 9 years ago. It seems like only yesterday. I was able to rummage through some of my old videotapes the other night, and I finally found this footage and was able to download an MPEG converter and get it uploaded. I did my college internship for my Broadcasting degree at the station that aired this footage. I was actually working at another station, the ABC affiliate here in Lexington, as a production assistant when this was shot, so the reporter that talked to me decided not to put me on camera when I told him I worked for a competing station. This is my first Youtube video, so all comments are welcome, either on Youtube or directly to me via e-mail. Hope you enjoy!

73,
Michael KU4UV
Lexington, KY.
 
Power Line Misunderstandings  
by KU4UV on July 19, 2008 Mail this to a friend!
Here is the link to the Youtube video

http://www.youtube.com/watch?v=OAm0q0YF1RQ

Enjoy!
KU4UV
 
Power Line Misunderstandings  
by KY1V on July 19, 2008 Mail this to a friend!

Nice article. Thanks.

So, does this mean it is dangerous for people whom ride their motorcycles and ATV's along the power lines routes?

when I was a kid, I recall riding under the power lines, motorcycles in the summer and snowmobiles in the winter.

David ~ KY1V
 
RE: Power Line Misunderstandings  
by K5END on July 19, 2008 Mail this to a friend!
quote, "So, does this mean it is dangerous for people whom ride their motorcycles and ATV's along the power lines routes?"

Riding in the right of way (ROW) is less safe than riding otherwise, with all else being equal.

Note that the winter snows often bring ice, the weight of which will either cause trees to fall into the lines or cause the lines to come down some other way. In any case you don't want to be anywhere around when it happens.

Seems like the distribution ROW (usually poles instead of towers, voltages between 1,200 and 35,000 Volts) is more associated with accidents.
 
RE: Power Line Misunderstandings  
by N3OX on July 19, 2008 Mail this to a friend!
"So what is 1 Joule/Coulomb? "

Roughly a twelfth of what my rig needs...
 
RE: Power Line Misunderstandings  
by W4LGH on July 20, 2008 Mail this to a friend!
N3OX said to..."So what is 1 Joule/Coulomb?"

...Roughly a twelfth of what my rig needs!
================================================
Would that be transmit or receive? Actually more
like IDLE!!

73 de W4LGH - Alan




 
RE: Power Line Misunderstandings  
by K5END on July 20, 2008 Mail this to a friend!
.
"...Roughly a twelfth of what my rig needs!"


Good one.

:-)



 
RE: Power Line Misunderstandings  
by N3OX on July 20, 2008 Mail this to a friend!
"Would that be transmit or receive? Actually more
like IDLE!! "

Alan, I think you're thinking of Joules per Coulomb*Ohm ... ohm

ohm...

ohm..
ohm..

Sri, got me one of 'em newfangled echo microphones...

 
RE: Power Line Misunderstandings  
by G8UBJ on July 21, 2008 Mail this to a friend!
"The voltages on distribution power lines (typically 1200 V to 35,000 V) are higher than most people can comprehend"

And then some. peak to peak AC is some 1.414 time greater!

So 120v ac is actually 169 volts Peak to peak
or in the UK 240v ac is 340 volts Peak to peak!

If thats 35,000 RMS it will be @50kv!!!

Either way get too close & death will occur so fast you won't be able to tell the 15kv difference.

BTW that includes railway overhead distributions systems which in most of Europe run at 25kv and regardless of endless safety campaigns kill many children over the summer break..
 
RE: Power Line Misunderstandings  
by K5END on July 21, 2008 Mail this to a friend!
"you're thinking of Joules per Coulomb*Ohm ... ohm
ohm...
ohm..
ohm..
Sri, got me one of 'em newfangled echo microphones... "

I thought you were doing some sort of New Age faux Eastern chant thing. :-)

ohhhhhhhmmmmm...
 
Power Line Misunderstandings  
by N4VNZ on July 21, 2008 Mail this to a friend!
Good discussion.

A couple of years ago, whilst on the long drive to the Dayton hamfest, I wondered aloud to my fellow ham travelers as to why power lines are not buried in the ground? Seems that we found several drawbacks to that, but I cannot recall what they were.

My power lines coming into my house are buried, so why couldn't HV transmission lines and distribution lines be buried? The construction cost would not seem to be more than the tons of steel and whatever necessary to elevate the lines.

So why can't they be buried in the ground?

Dave
 
RE: Power Line Misunderstandings  
by K5END on July 22, 2008 Mail this to a friend!
Sometimes they are buried, or at least they are run inside underground vaults.

Consider a downtown area in a major city. You'll see substations on the perimeter, but few if any power poles along the streets next to the skyscrapers.

Of course they have to be insulated conductors, limiting the voltage.

It's more expensive this way too.

Direct burial of the bare conductors at high voltage would not work. The ground would be energized and there would be significant loss of power.
 
RE: Power Line Misunderstandings  
by G3RZP on July 22, 2008 Mail this to a friend!
The other problem is that the capacitance between conductors becomes a problem, especially up at the several hundred kV level.

When the undersea lionk from England to France was first tried 40 odd years ago, it was found that losses when using AC were too high because of the capacitance. Not only is there power factor caused by capacitance, but there's dielectric loss, too, even at 50 Hz. It builds up over miles of cable. That's why that link is HV DC.
 
RE: Power Line Misunderstandings  
by K5END on July 22, 2008 Mail this to a friend!
"The other problem is that the capacitance between conductors becomes a problem, especially up at the several hundred kV level.

When the undersea link from England to France was first tried 40 odd years ago, it was found that losses when using AC were too high because of the capacitance. Not only is there power factor caused by capacitance, but there's dielectric loss, too, even at 50 Hz. It builds up over miles of cable. That's why that link is HV DC."

Excellent point and an excellent example!

How intriguing. I hadn't thought of capacitance affecting the power factor. Usually the utility has to ADD capacitance to compensate for the VARs and reduce the PF, at least around here. Never assume!:-) Thanks for posting that.
 
Power Line Misunderstandings  
by AA8EE on July 28, 2008 Mail this to a friend!
When I am out in the yard using an aluminum extension ladder, and not really knowing the voltage of the lines on the poles along the back fence line of my lot, how far away should I stay?
Can dangerous voltages be induced into such a conductive ladder? At what distance?
 
RE: Power Line Misunderstandings  
by K5END on July 28, 2008 Mail this to a friend!
I wouldn't use an aluminum ladder anywhere near power lines.

Period.

 
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