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  1. #1
    Ron Bishop's Avatar
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    Default High voltage power lines

    During an inspection today, I saw a romex conductor by this chain link fence, and when I brought my current tester up to it it signaled current at the concuctor. A closer look at the conductor revealed that it wasn't connected to any electrical supply, but was connected to a ground rod by the fence. Just for fun, I turned off the main circuit breaker to the house, and brought up a second current tester. Not only were both conductors detecting current, but the chain link fence was setting off both of my testers as well. They were going off starting about 15 feet away from the fence. The chain link fence on the right did not set off my testers. I didn;t have a voltage tester, and had already touched the fence and didn't receive a shock. The only thing I can think of is the presence of static electricity coming from the high voltage power lines almost directly overhead. Any thoughts?

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  2. #2
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    Default Re: High voltage power lines

    You said current testers, and that you didn't have a voltage tester ... I am confused. Did you mean you have voltage testers such as voltage sniffers but not a voltmeter?

    Did you hold the voltage sniffer in the air and check that? My guess is that your voltage sniffer was picking up the reading from the high voltage power lines, and that if you had checked anywhere in the air you would have also gotten a reading, without even being close to the fence.

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: High voltage power lines

    Quote Originally Posted by Jerry Peck View Post
    Did you hold the voltage sniffer in the air and check that? My guess is that your voltage sniffer was picking up the reading from the high voltage power lines, and that if you had checked anywhere in the air you would have also gotten a reading, without even being close to the fence.
    I ask because I have found several which did that, and they were not even under those high voltage lines, they were under medium voltage lines, probably 26 kv or so, yours were likely 138 kv or more.

    Jerry Peck, Construction / Litigation Consultant
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  4. #4
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    Default Re: High voltage power lines

    You are correct...I had 2 sniffers but no voltmeter with me. One of the sniffers turns ble when it detects within 12 inches, then red within 2 inches of current. It became red when held with 2 inches of the fence.


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    Default Re: High voltage power lines

    I've never tested it but have heard that it is possible to hold a florescent tube in the air parallel to those high voltage lines and have it light up. No doubt you would have induced voltage in a conductor under those lines just like the secondary winding in a transformer. Did your hair stand on end?

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  6. #6
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    Default Re: High voltage power lines

    what hair? it is a cue ball up there!


  7. #7
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    Default Re: High voltage power lines

    bold red is mine
    Quote Originally Posted by Ron Bishop View Post
    You are correct...I had 2 sniffers but no voltmeter with me. One of the sniffers turns ble when it detects within 12 inches, then red within 2 inches of current. It became red when held with 2 inches of the fence.
    "voltage"

    Those are "voltage" sniffers.

    The first one I found stumped me as anywhere in the back yard would set my voltage sniffer off if I moved it higher than about 4 feet above the ground. But it picked up nothing if I kept it down around 3 feet above the ground or lower. I was checking an above ground pool ladder and the ladder sent my sniffer off ... then as I was walking around checking them metal walls of the pool I realized that even when I was not holding it near the pool it would go off, so I started moving it up and down and found the point at which it went off, then walked around and it did it everywhere I walked in the rear yard.

    At the time I did not have an ELF-EMF tester, but I imagine it would have sent it off the scale.

    Shortly thereafter I had a client wanted ... demanded ... that I check ELF-EMF at the houses I was inspecting for them, so I bought one, did my research on what I was checking for, how to check for it and what protocols there were (was only one, from out in California from one of the universities).

    My client essentially paid for the tester on the first inspection I used it on, and then paid for it multiple times over on each additional inspection until they decided which house to buy. After that, though, I rarely used it, maybe once or twice was all.

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: High voltage power lines

    Quote Originally Posted by Jerry Peck View Post
    At the time I did not have an ELF-EMF tester, but I imagine it would have sent it off the scale.

    Shortly thereafter I had a client wanted ... demanded ... that I check ELF-EMF at the houses I was inspecting for them, so I bought one, did my research on what I was checking for, how to check for it and what protocols there were (was only one, from out in California from one of the universities).
    You didn't finish your story, I've been holding my breath..... so after you got the emf tester.... is you backyard a hot spot or was it just a false sniffer ?

    Joe Klampfer RHI
    www.myinspection.ca
    Pacific Home Inspections

  9. #9
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    Default Re: High voltage power lines

    I can't say this is the case here, but ...

    Severasl times I have found buried cables that were damaged when the fence was installed. It's not impossible that the arrangement you saw was an attempt to 'ground' the fence. If so ... well, it didn't work, did it?


  10. #10
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    Default Re: High voltage power lines

    By running the gate parallel to the electrical lines they possibly and inadventantly built a tranformer, not a very good or efficient one but minamally functional yes.


  11. #11
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    Default Re: High voltage power lines

    Interestingly enough, the portion of fence that was parellel to the power lines detected voltage, but the one perpendicular did not.


  12. #12
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    Default Re: High voltage power lines

    There had also been an electric fence installed at one time, but had been previously removed.


  13. #13
    Ron Bishop's Avatar
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    Default Re: High voltage power lines

    ok..so what if any would be the danger to a human living there?


  14. #14
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    Default Re: High voltage power lines

    Some would say long-term exposure to the electromagnetic field these power lines emit could lead to/increase the risk of cancer for occupants living near a large power line. I certainly don't know the answer to this but ... a woman I dated lived underneath one of these high voltage towers for years and developed breast cancer in her 40's - she thinks it's a contributing factor. Luckily, she had very good insurance (a government employee), a very good doctor and lots of family support.


  15. #15
    Phil Brody's Avatar
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    Default Re: High voltage power lines

    There have been numerous studies and there has been no positive link to any deleterious effect, except resale value.


  16. #16
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    Default Re: High voltage power lines

    I have a Greenlee multimeter that will test for fields. Sometimes I will turn on this feature just to show the guys NOT to rely on it entirely. I can walk in a substation and wear the batteries out with the meter signaling all over everything. Hold your tester straight up toward the lines as someone else has suggested, It doesn't take much to set them off.


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    Default Re: High voltage power lines

    Check this link out and decide for yourself what you want to relate to your clients.....

    Living By Power Lines


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    Default Re: High voltage power lines

    Quote Originally Posted by Joe Klampfer View Post
    You didn't finish your story, I've been holding my breath..... so after you got the emf tester.... is you backyard a hot spot or was it just a false sniffer ?
    I did finish my story.

    That was not my backyard where the sniffer went off.

    After I got my ELF-EMF tester I never went back to that house, it was a couple of years later.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
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  19. #19
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    Default Re: High voltage power lines

    This reminds me of the following:
    Last summer I was watching my daughter at a horseback riding class and it was drizzling. I walked with my kid around the arena fence, and without knowing, getting closer to a high-voltage power line. I felt that we both had current when I touched him in the hand. I thought it was just the static and played a little but was, surprised how long it was lasting. I looked up as he said that it felt like a hard scratch in his arm and it was hurting a little.

    This event scared the crap out of me ( I have seen and been involved in pretty crazy stuff) ,when I remembered when someone was delivering metal sheets with a crane close to a high voltage power line while it was drizzling . The tires of the truck blew off and the standing crane operator died instantly. I donít know how far the crane was from the power line and I assume that people should have more common sense sometimes. But the truth is bad things happen all the time. Be careful people!


  20. #20
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    Default Re: High voltage power lines

    Quote Originally Posted by Jim Hintz View Post
    Check this link out and decide for yourself what you want to relate to your clients.....

    Living By Power Lines
    Jim,

    That is a VERY biased page, not scientific at all, but from ELF-EMF as health danger promoter types, as evidenced by this:
    "
    Living by power lines has been known to increase the risk of leukemia and other cancers since 1979, when convincing evidence was first published by Werthimer and Leeper .
    "

    There is no scientific proof which shows a direct connection, thus the statement "has been known" is incorrect.

    For those studies to be scientifically proven, in addition to many other things, those studies would need to scientifically prove that there were no other potential causes.

    Some of the first studies were in, as I recall, some towns in France, and there manufacturing plants and chemical plants nearby which were not addressed by the studies to show the problems were not associated with those plants, and there were no water quality studies done to show those problems were not associated with the water, nor were there any air quality studies done to show those problems were not associated with the air ... in short, the tests were performed TRYING TO FIND A LINK to ELF-EMF and not done in a manner TRYING TO FIND THE CAUSE and eliminate other influences which were not part of the causation.

    In short, if you go looking for frogs, and you go to a lake, and you find frogs, that does not mean that the lake causes frogs.

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: High voltage power lines

    Quote Originally Posted by Ron Bishop View Post
    ok..so what if any would be the danger to a human living there?
    I would recommend orienting the bed so it is perpendicular to the power lines, and avoid wearing the tin foil beanie.

    Seriously, if you strung enough fencing parallel to the power lines, you could probably charge a banks of batteries and get at least some of your power that way. Maybe with cost of generating going up all the time, power companies should tap some of that power by running wire below the transmission lines.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

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    Default Re: High voltage power lines

    The beatings will continue until morale has improved. mgt.

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    Default Re: High voltage power lines

    Vern, your attempts to post a link to the thread you to which you refer, didn't work.

    Here's a direct, clickable link to Vern's topic thread:

    http://www.inspectionnews.net/home_i...ch-ladder.html


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    Default Re: High voltage power lines

    The fence section is insulated from the ground and isolated and is not properly grounded.

    The following are from notes circa much earlier last decade (early 2000's), and am not inclined to engage in the research to update them, but here goes (applicable at that time, to California, references):

    Title 8 CCR, Section 2700, "High Voltage Electrical Safety Orders" Defines minimum requirements and standards for installation, operation and maintenance of electrical facilities to provide practical safety and freedom from danger.

    ANSI/IEEE Standard 80-2000; "Guide for Safety in AC Substation Grounding" Provides guidelines and calculation to design a safe and effective electrical grounding system within an electrical facility.

    NESC, ANSI C2, Section 9, Article 92, Paragraph E; Article 93, Paragraph C Defines grounding methods for electrrical supply and communications facilities.

    Title 14 CCR, Section 1250-1258, "Fire Prevention Standards for Electric Utilities" Provides specific exemption from electric pole and tower firebreak and electric conductor clearance standards and specifies when and where standards apply.

    General Order 95/128, "Rules for Overhead Line Construction" Provides requirements for electrical overhead construction in California.

    Electric fields are invisible lines of force created by voltage, and are shielded by most materials. Units of measure are volts per meter (V/m). Magnetic fields are invisible lines of force created by electric current and are not shielded by most materials, such as lead, soil and concrete. Units of measure are Gauss (G) or milliGauss (mG - 1/1000 of a Gauss). Electric and magnetic field strengths dimmish with distance. These fields are low energy, extremely low frequency fiels, and should not be confused with high energy or ionizing radiation such as X-rays and gamma rays.

    Induced Currents

    The primary issue is how the induced or coupled voltages and currents on these objects can compromise safety to a person who is expose to the object. Researchers have done extensive work in the area of perception of 60 Hz power system currents. The electrical effects on humans starts with perception and as current levels increase, let-go levels are next in importance. Higher current levels can lead to ventricular fibrillation and respiratory inhibition, which can cause death. Generally, for safety purposes, it is desirable to reduce the induced voltage and currents to levels that result in current flow through the body below the let-go threshold. Ultimately sufficient safeguards should be provided to reduce body currents below the perception limit. The reported perception of electrical current is a median level of approximately 1.0 milli-Amp (1/1000 of an ampere referre to in a conensed unit of "mA"). The let-go threshold is defined as the highest current (Root Mean Square which represents an average) flow in a hand tohand or hand to foot path for which a conductor held in a hand may be released. This threshold is extremely important since it defines a minimum dangerous current for the onset of an uncontrollable situation. The average let-go current for women and men was found to be 10.5 mA and 16.0 mA, respectively. In the smallest percentile for let-go currents measured, the currents have been reported to be as low as 6.0 mA for women and 9.0 mA for men. It has been estimated that 4.5 mA would be a reasonably safe let-go threshold for children. The National Electrical Safety Code (NESC) requires that power lines be designed to keep the induced current from nearby objects below 5.0 mA when short-circuited to ground. The short circuit current can be calculated for any object in or near the corridor to determine if the magnitude of the current is below the 5.0 mA rule for safety purposes.

    The other situation in terms of electrical currents is a fault current. This would be a current, which flows to ground because of an abnormal situation on the power line such as a broken conductor. The fault current is primarily a function of the time it takes the utility to clear the fault. As the time of exposure decreases the body tolerance to current levels increases.

    Fire and Fuel Ignition

    Fires and possibly fuel ignitiion could result if there is a certain amount of energy. One example that is often analyzed is the fueling of a vehicle near a power line. It has been found that the amount of energy to cause ignition of a fuel mixture is in the order of 0.25 millijoules. These energy levels are possible from a high voltage line but for a fuel mixture to be ignited, there are other conditions that would have to occur as follows:
    • the vehicle being fueld would have to be well insulated from ground,
    • the spout of the fuel container would have to be well grounded, and
    • the fuel mixture would have to be a certain proporation and concentration of gases.
    It is generally recommended that fueling operations do not take place within the transmission line right of way (ROW).

    Electric Induction - General

    The magnitude of electric field strengths from transmission line operation should not produce significant induced currents in objects near the corridor. The NESC requires a 5.0 mA limit based on the clearance from the transmission line to objects in proximity of the line. It is also known, that an induced current level of 1.0 mA can be perceived by human beings. Typically, grounding the object will eliminate the possibility of a person being subjected to induced currents from these objects.

    The issue of exposure to magnetic fields from current carrying sources has been the subject of debate for many years. There are no proven health effects of magnetic fields from electric power facilities such as power lines. Magnetic field strength is a function of current flows in the line as well as conductor and phasing configuration. If there is a concern about reducing magnetic field strength some common mitigation shemes such as alternate conductor and phasing configurations could be investigated to study potential mitigation.

    Numerous internationally recognized scientific organizations and independent regulatory advisory groups have conducted scientific reviews of the EMF research literature (see footnote). Without exception, these major reviews have reported that the body of data, as large as it is, does not demonstrate that exposure to power-frequency (60 Hertz [Hz] in the U.S.) magnetic fields causes cancer or other health risks, although the possibility cannot be dismissed. Most reviews recommend further research, and appropriately, research is ongoing worldwide. The weakness of the reported associations, the lack of consistency, and the severe limitations in exposure assessment in the epidemiology studies together with the lack of support from laboratory studies were key considerations in the findings of the scientific reviews.

    footnote: CPUC/CDHS, 1989, IRPA/INIRC, 1990; ACGIH, 1991; EPA, 1990; EPA-SAB, 1992; CIRRPC, 1991; EMHEC, 1992; NRPB, 1992; Illinois, 1992; Colorado, 1992; Case, 1992; ORAH, 1992, 1993; INSERM 1993; Danish Ministry of Health, 1993; Universities Consortium on Electromagnetic Fields, Connecticut (February 1994); National Radiological Protection Board, United Kingdom (April 1994), American Meical Association (January 1995); American Physical Society (May 1995); American Cancer Society (January 1996); Virginia Department of Health (February 1996): National Academy of Sciences (January 1997); NIEHS Director's Report to Congress (June 1999).

    U.S. Federal EMF Program

    In 1992, the U.S. Congress authorized the Electric and Magnetic Fields Research and Public Information Dissemination Program (EMF-RAPID Program) in the Energy Policy Act (PL 102-486, Section 2118). The Congress instructed the National Institue of Environmental Health Sciences (NIEHS), National Institutes of Health and the Department of Energy to direct and manage a program of research and analysis aimed at providing scientific evidence to clarify the potential for health risks from exposure to ELF-EMF. This program was completed in December 1998. In June 1999, NIEHS published its report (Health Effects from Exposure to Power-Line Frequency Electric and magnetic Fiels) with its findings and conclusions from this program of research.

    The 1999 NIEHS report states the following in its conclusion section:
    The scientific evidence suggesting that ELF-EMF exposures pose any health risk is weak... The NIEHS concludes that ELF-EMF exposure cannot be recognized as entirely safe because of weak scientific evidence that exposure may pose a leukemia hazard. In our opinion, this finding is insufficient to warrant aggressive regulatory concern.
    Panels charged with recommending exposure limits for electric and/or magnetic fields have concluded that no meaningful experimental data exists (e.g., no dose-response information is available) on which to base standards or limits to which the public is exposed.


    Electric Induction - Structures

    Typically, buildings and storage sheds will not be permitted within the utility corridor, and are not a particular concern. However, lower electric field strengths can also exist outside of the corridor and buildings outside of the corridor should be considered. For structures outside of the right of way (ROW), it is easy to reduce the potential for startle or annoyance possiblities by attaching a ground wire to the metal roof, etc. This protection also provides a measure of lighting protection for the structure. Buildings entirely made of metal are not normally of any concern because they are often inherently well grounded, but exceptions might xist for structures on wood foundations, or on a high-resistance material. Again it is usually a simple matter to ground such objects if necessary.

    In the same manner, rain gutters on a large house fairly close to the transmission line could conceivably deliver a perceptible shock to a person on an aluminum ladder. Quantitative worst-case analysis of any particular case can be difficult, but it is possible to determine if reducing the potential for perceptible shocks is a prudent precaution. It is a simple procedure to attach a wire to the downspout and ground it to a metal water pipe or a driven ground rod to mitigate shock effects.

    Electric Induction - Fences

    Long fence wires that are strung on wooden posts can present shock possibilities if they run more or less parallel and close to the transmission line. The insulation quality of the wooden posts is the controlling parameter. Perpendicular fences will have significantly less induced current and voltage. When exposed to the weather, even wooden posts are not perfect isulators. The lack of insulation will reduce the induced voltage on a fence wire and will limit the magnitude of a spark discharge.

    Nevertheless, some fences could be insulated enough by the posts to make contact currents annoying when the fence is touched. This type of fence would have to be lose to the line and quite long before it produced annoying currents.

    Long fences are often grounded by contact with growing vegetation. If grounded in this manner, electric field effects will be reduced, although magnetic field effects will remain unaffected. The possiblity of annoyance due to electric field induction could be eliminiated by solidly grounding the fence at a single point, such as with a metal fence post.

    For an "electric fence," this is accomplished with a special filter designed to drain only the induced charge. However, a fence that is grounded at one or more points and otherwise insulated along a sufficient distance could present some opportunity for noticable magnetic field induction effects. Reducting the potential of these effects requires electrically breaking the fence into smaller grounded sections.

    The insulation of a person's shoes does not always reduce the current he receives due to electric field induction on a fence or any other conductive object; however, currents due to magnetic field induction are very sensitive to a person's shoe resistance. Shoe resistance will usually limit magnetically induced currents to an insignificant level. On the other hand, if a person is not well insulated from the ground (e.g. barefoot and on damp earth), there is a greately increased chance for significant magnetically induced current on contact with a long fence.

    There is no known incidence of injury due to induction on fences. Nevertheless, as a precuationary measure and to preclude annoyances, both magnetic and electric field induction effects can be potentially reduce by grounding at periodic distances along fences AND by breaking the electical continuity of long fence wires that are close to high-voltage transmission lines.

    Electric Induction - Agriculture Equipment

    Agricultural equipment can have dimmensions approaching those of large road vehicles and as such can be subject to similar electric field induction levels. In practice, the conductivity of tires and good contact with the soil usually insures that electric field induction on farm equipment is seldom perceived.

    Irrigation systems often incorporate long runs of metallic pipelines, which can be subject to magnetic field induction when located parallel and close to power lines. Because of the pipes' contact with moist soil, electric field induction is generally negligible, but annoying currents could still be experienced from magnetic coupling to the pipe. Pipe runs laid at right angles to the line will minimize magnetically induced currents although such a layout is not always feasible. Common mitigation measures are grounding and/or insulating the pipeline runs.

    Operation of irrigation systems beneath power lines presents another safety concern, particularly for systems that can project the water to conductor height. This concern is not caused by induction, but rather by the possiblity of direct contact by conductive water. The water stream from a high-pressure nozzle generally consists of a solid and broken-up portion. If the solid stream contacts an energized conductor, electric current conducted down by the water stream may be hazardous to someone contacting the nozzle. Line contact by the broken-up part of the water stream is unlikely to present any hazards.

    Although there are these legitimate concerns regarding irrigation systems, the only known and unfortunately not infrequent cause of serious accidents is inadvertent contact to lines by upended irrigation pipes, often during an attempt to remove a small field animal that has crawled into the pipe. For this reason, irrigation pipes that are very close to any power line should be moved with caution. The pipes must never violate a safe electrical clearance around line conductors.

    Magnetic Induction - Pipelines

    Metallic pipelines can be within the transmission right of way (ROW). Magnetic fields penetrate the ground and significant impacts can occur with long pipelines (there is not an established length but typically pipeline lengths more than 1,000 feet become more of a concern). Maximum voltages on the pipeline occur where there are discontinuities in either the transmission line or pipeline. When the transmission line and a pipeline are interacting, such discontinuities take the form of rapid changes in:
    • Separation between the pipeline and transmission line
    • The termination of the pipeline or an insulating junction in the pipeline (which amounts to the same thing)
    • Sudden changes in pipeline coating characteristics
    • A junction betwen two or more pipelines or transposition of transmission line phases
    Note that the induction effects on pipelines during normal power line operating conditions are small compared to the induction effects experienced by a pipeline during a power line fault. The most severe kind of fault is a single phase-to-ground fault, during which high currents circulate in one of the power line phases and are not attenuated by any similar currents in other phases. Hence, fault reuction methods that suffice for single-phase fault conditions are often adequate for other conditions. In spite of the relatively low magnetic field levels during steady state conditions, induced voltages on an unprotected long metallic structure can reach hundreds of volts. The highest magnetically induced voltages occur for a gault condition since the currents in the line can be an order of magnitude greater than the normal or emergency load current.
    Even with extensive grounding systems connected to the structure, pipeline potentials can be on the order of dozens of volts, with hundreds of amps flowing in the structure. This constitutes primarily a shock hazards, which can be transferred miles away from the parallel corridor. In magnetic coupling studies, it is important that power lines as far away as 1,000 feet or more from the power line under study be given serious consideration.

    Generally, there are three techniques to reduce the potential for high magnetically induced voltages below unsafe levels for fences, pipelines and railroad track systems:

    • Sectionalize the conductor system -- electrically isolate the pipeline, fence, etc. in sections to keep the voltages down to a minimum without the opportunity to build up over long distances.
    • Ground the conductor system -- put grounds on the conductor system at key locations where the conductor system and transmission line change characteristics and locations relative to each other.
    • Buried fault reduction wires -- install another system of parallel conductors to the pipeline, fence, etc. at key locations to allow the voltages of the multiple conductors to equalize to a common potential thus creating a low potential difference across a person's body that will not be unsafe.
    Fire Hazards

    The proximity of the transmission line to objects in or near the corridor can be susceptible to fires because of one of the following effects:
    • A direct flashover to the object if the object is less than a minimum clearance to cause an electric arc between the line and the object
    • A spark discharge on the object as a result of an increase in voltage between the object and ground
    Air has a very high electrical insulation value (capable of sustaining up to 30,000 volts per centimeter) which aids in reducing the susceptibility of an arc discharge occuring. It has been determined that a voltage around the line of 100,000 volts is required to cause wood (such as a tree) to burn (the assumption is that the wood is moist). For a 69kV line, this would require that the wood object was less than three feet from the line. Therefore, it is prudent to clear brush, trees and other combustible materials that are less than three feet from the line.

    One of several papers on methods for calculating induced voltages on metal/wire fencing and pipelines by AC power transmission lines:

    Induced voltages on fence wires and pipelines by AC power transmission lines

    Abdel-Salam, M. Al-Shehri, A.
    Dept. of Electr. Eng., King Fahd Univ. of Pet. & Miner., Dhahran, Saudi Arabia;
    This paper appears in: Industry Applications, IEEE Transactions on
    Publication Date: March-April 1994
    Volume: 30 , Issue: 2
    On page(s): 341 - 349
    ISSN: 0093-9994
    CODEN: ITIACR
    INSPEC Accession Number:4708413
    Digital Object Identifier: 10.1109/28.287525
    Current Version Published: 2002-08-06


    Abstract
    A method is developed for calculating the induced voltages on fence wires/pipelines underneath AC power transmission lines. The method is based on the charge simulation technique and takes into account the disturbances of the electric field and potential due to the presence of the fence wire/pipeline underneath the line. The calculated values of the induced voltage on fence wires are compared with those measured before. Induced voltages on pipelines underneath 230- and 380-kV lines are measured, correlated to the calculated values and discussed in the light of electric field induction on objects adjacent to AC power transmission lines

    In summary,

    Lightning

    Power poles, like trees and other tall objects are more likely to intercept lightning strikes. Transmission lines are therefore usually built with a grounded shield wire at the top of the poles. This protects the transmission line from lightning. Lightning is not more likely to strike houses or cars near the transmission line. Shorter objects under or very near a line may actually receive some protection from lightning.

    Induced Voltage

    People or animals can receive a shock by touching a metal object located near a transmission line. The shock is similar to that received by touching a television after walking across a carpet. The magnitude and the strength of a charge are directly related to the mass of the ungrounded metal object and its orientation to the transmission line.

    Induced current can be prevented or corrected by grounding metal objects near the transmission line. Grounding chains can be installed on tractors. Metal fences can be connected to a simple ground rod with an insulated lead and wire clamp. Electric fences with proper grounding should continue functioning properly even when subject to induced voltage.

    Stray Voltage

    For the past 20 years, stray voltage has been vigorously studied. Electrical systems are grounded to the earth to ensure safety and reliability as required by the National Electric Safety Code (NESC). Because of this, some current flows through the earth at each point where the electrical system is grounded and a small voltage develops. This voltage is called neutral-to-earth voltage (NEV). When NEV is measured between two objects that may be simultaneously contacted by an animal (even a human "animal"), it is considered stray voltage.




  25. #25
    Join Date
    Jul 2008
    Location
    Snowbird (this means I'm retired and migrate between locations), FL/MI
    Posts
    4,086

    Default Re: High voltage power lines

    Quote Originally Posted by Ron Bishop View Post
    Interestingly enough, the portion of fence that was parellel to the power lines detected voltage, but the one perpendicular did not.
    Quote Originally Posted by Ron Bishop View Post
    There had also been an electric fence installed at one time, but had been previously removed.
    The perpendicular, taller, properly constructed chain link fence is likely owned by the power transmission Right-Of-Way occupant, and is likely properly grounded.

    The HO's parallel fence, is of issue. The existance of romex, and the visual indicate it is neither properly constructed, nor has any previous "electrification" been properly and/or completely abandonded, nor remediated, and as described, the fence section parallel is NOT properly grounded (independant and isolated of the premisis wiring system).

    It is also apparent that the pictured is not as would have been original if permitted, (i.e. permit issued for structure, i.e. parallel fence) and has been altered/modified and not maintained as per California safety requirements, especially in proximity to ROW and power transmission lines. It is also highly probable that there also exists pipeline in the ROW.


  26. #26
    Join Date
    Mar 2010
    Location
    conyers, ga
    Posts
    75

    Default Re: High voltage power lines

    Had one house that was a long way from the main road and overhead power and older phone lines ran about 500 feet before the house where the transformer was located.
    Later a new underground phone line replaced the overhead phone lines but the overhead phone lines were never removed and not connected on each end. when the phone tech was attempting to complete the new wiring hookup at the terminal block on the side of the house he touched the end of the old phone line and received a very painful shock. We tested and we were reading very high voltage on that wire. I hooked up a wall outlet tester with the three neon bulbs, to the hot side and the neutral side to a ground wire and lit the bulb :-)
    So there is quite a lot of conduction from power lines and these were just the residential supply lines.
    I have also heard of farm animals that are located under/near those higher voltage lines exhibit stunted growth ?
    I would imagine continuous close proximity to those higher voltage lines would not be good.


  27. #27
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,248

    Default Re: High voltage power lines

    There are three distinctly different phenomenons being discussed/brought up in the above posts.

    1) Extremely Low Frequency Electro Magnetic Fields - These are magnetic fields crated by the 60 Hz current fluctuations in the high voltage power lines ... the same thing happens to a much lesser extent the lower the voltage is.

    2) Electrostatic voltage produced by the high voltage power lines.

    3) Stray and induced currents which are induced into a conductor running parallel with the power lines. Like any generator, a conductor moving through a magnetic field, or, the magnetic field moving through a conductor (in this case the 60 Hz cycle of the voltage and current in the high voltage power lines) produces current flow in the conductor. Current flowing through a conductor (a resistance) creates voltage based on that current flow and the resistance. Thus the stray or induced currents create stray or induced voltage across the resistance of the conductor.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

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