“Stray voltage is manmade electromagnetic energy that directly affects livestock. Most of it is associated with the electrical power distribution system. Much of the increase in stray voltage we have seen in the past 30 years is due to aging distribution systems, heavy loads on existing systems, and an increasing reliance on the earth as a conductor for the power system.” (From the deposition of Alex Furo in the landmark case brought by the Attorney General of Michigan against an electric utility.)
|Transient electric and magnetic fields would induce higher current density in a child’s body than power frequency fields with similar field strength.|
| Low-frequency transient electric and magnetic fields coupling to child body S. Ozen* |
Department of Electrical and Electronics Engineering, Engineering Faculty, Akdeniz University, 07058 Antalya, Turkey
*Corresponding author: email@example.com
Much of the research related to residential electric and magnetic field exposure focuses on cancer risk for children. But until now only little knowledge about coupling of external transient electric and magnetic fields with the child’s body at low frequency transients existed. In this study, current densities, in the frequency range from 50 Hz up to 100 kHz, induced by external electric and magnetic fields to child and adult human body, were investigated, as in residential areas, electric and magnetic fields become denser in this frequency band. For the calculations of induced fields and current density, the ellipsoidal body models are used. Current density induced by the external magnetic field (1 µT) and external electric field (1 V/m) is estimated. The results of this study show that the transient electric and magnetic fields would induce higher current density in the child body than power frequency fields with similar field strength.
|The presence of the RF magnetic fields on power lines must be considered in the context of epidemiologic studies.|
| Radiofrequency exposure near high-voltage lines Vignati, M.* and L. Giuliani |
Environmental Health Perspectives 105, Supplement 6, December 1997
Istituto Superiore Prevenzione e Sicurezza del Lavoro, Rome, Italy
*Corresponding author: Dr. M. Vignati, Istituto Superiore Prevenzione e Sicurezza del Lavoro, Via Urbana 167, Rome 00184, Italy. Telephone: 39 6 471 4243. Fax: 39 6 474 4017. E-mail: firstname.lastname@example.org
Many epidemiologic studies suggest a relationship between incidence of diseases like cancer and leukemia and exposure to 50/60 Hz magnetic fields. Some studies suggest a relationship between leukemia incidence in populations residing near high-voltage lines and the distance to these lines. Other epidemiologic studies suggest a relationship between leukemia incidence and exposure to 50/60 Hz magnetic fields (measured or estimated) and distance from the main system (220 or 120 V). The present work does not question these results but is intended to draw attention to a possible concurrent cause that might also increase the incidence of this disease; the presence on an electric grid of radiofrequency currents used for communications and remote control. These currents have been detected on high- and medium-voltage lines. In some cases they are even used on the main system for remote reading of electric meters. This implies that radiofrequency (RF) magnetic fields are present near the electric network in addition to the 50/60 Hz fields. The intensity of these RF fields is low but the intensity of currents induced in the human body by exposure to magnetic fields increases with frequency. Because scientific research has not yet clarified whether the risk is related to the value of magnetic induction or to the currents this kind of exposure produces in the human body, it is reasonable to suggest that the presence of the RF magnetic fields must be considered in the context of epidemiologic studies.
|Papers on Electrical Pollution by Dr. Martin Graham, Professor Emeritus at University of California in Berkeley|
| Dr. Graham has written a several ground breaking papers on how to measure and mitigate electrical pollution.|
“A Ubiquitous Pollutant”
Dated 28 October, 2000, Dr. Graham details an instrument that plugs into regular outlets and measures the high frequencies present on the electrical wires. Unfortunately, the Fluke 79 III only measures frequencies up to 20 kHz. It is probable that frequencies higher than 20kHz are present on the line. The frequency window can be expanded by using another rms meter with a greater frequency window and meets the other requirements. The filter can also be used with an oscilloscope (again be aware of the frequency limitations of the instrument).
“Mitigation of Electrical Pollution in the Home”
An inexpensive hand held AM radio can be used to make preliminary measurements to detect electrical pollution. Each filter is made from a 20µf motor run A.C. dry film capacitor with a bleeder resistor (for safety) and a properly attached cord. (The A.C. dry film capacitor used in the initial test filters was the Panasonic JSU18X206AQD.) Approximately 20 such filters are needed to reduce exposure to electrical pollution in the home. These filters have advantages over previous filters in that they are small, portable (They plug into any outlet.), filter higher frequencies (over 100kHz), and any person who knows how to plug in an electrical cord can install them.
“A Microsurge Meter for Electrical Pollution Research”
Dr. Graham has also provided pictures of spectra of electrical pollution from a spectrum analyzer.
|Other Items of Interest|
| Dave Stetzer, an Industrial Power Quality Specialist from Stetzer Electric in Blair, WI, has provided waveforms illustrating the effect non-linear loads (e.g. dimmer switches and computers) have on power quality. The following papers by Donald W. Zipse, P.E. Life Fellow, IEEE should also be of interest:|
Electrical Shock Hazard Due to Stray Current: The Shocking Shower (IEEE Paper)
Are the National Electrical Code and the National Electrical Safety Code Hazardous to Your Health?: The Shocking Swimming Pool (IEEE Paper)
Look under Electrical Engineering for Electric Shock – Stray Current (IEEE Paper) or NEC – Dangerous To Your Health (IEEE Paper)
“Increased Levels of EMR in Buildings” by Martin Lundmark, Anders Larsson, Ake Larsson, and Patrik Holmlund discusses the problems caused by harmonics and high frequency noise: http://www.tt.luth.se/emconsite/artiklar/Greece2002.pdf
Excerpts of a letter written by Lloyd Morgan (Part 1 and Part 2), an Electronic Engineer with a BA in Electronic Engineering from University of California – Berkeley, and a member of Central Brain Tumor Registry of the United States.
|Cell tower strobing lights|
|In May 2001 some very high frequency signals appeared on equipment monitoring electrical ground currents at a few dairy farms in Wisconsin. The signal was traced to a nearby cell tower whose rotating beacon light had just recently been changed to a strobing light. The origin of the signal was verified by shutting off the strobing light momentarily. The signal on the monitoring equipment disappeared while the light was off. The signal starts at about 25 MHz and rings down from there. It is produced when the capacitors, which store up the 1000 volts or more needed to strobe the light, release that energy all at once to strobe the light. Therefore, a high frequency and high voltage impulse is released each time the light flashes. If the RF Choke is in place and the utilities wires are adequate to carry the current back to the substation, there is no problem. However, many companies, not realizing the problem they cause, have opted to save the approximately $30 and omit the filter. The utility system, in many areas, cannot return such a high frequency high voltage impulse to the substation on the neutral wire, as it should. Therefore, it takes the path of least resistance back to the substation. The path of least resistance is not always the shortest path. Problems have been found as far as 6 miles from the tower.|
|Electrical transients affect milk production|
|The review article by Dr. Donald Hillman, Professor Emeritus, Department of Animal Science, Michigan State University Effects of Electrical Shock on Cattle and abstract for the paper entitled Milk Production of Dairy Herd Decreased by Transient Voltage Events contain important information about the effect of electrical pollution on dairy cows. A graph from Milk Production of Dairy Herd Decreased by Transient Voltage Events shows a linear relationship between milk production and electrical transient exposure.|
|Electrical Engineers Please Take Note|
|It is important for electrical engineers making design decisions to realize that “dirty” power and electrical earth currents cause health and financial problems for humans and the livestock industries, so they can make decisions to reduce or eliminate these problems. The Electrical Power Research Institute (EPRI) and the Institute of Electrical and Electronics Engineers (IEEE), as well as some individual utility companies have identified solutions for electrical ground currents and “dirty” power. The solutions include larger primary neutral wires and/or filters to reduce the amount of high frequencies present. According to EPRI ” A method that practically eliminates ground currents associated with primary distribution lines and still maintains the advantages of a four-wire multi-grounded system, is the five-wire system…(excerpt from Handbook for the Assessment and Management of Magnetic Fields Caused by Distribution Lines).” An April 2002 IEEE paper entitled “Five-wire Distribution System Demonstration Project” contains similar findings.|