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Following the growing awareness in Israel of the possible effects of magnetic fields on human health, which was also reflected in the 2006 Radiation Law enacted at the initiative of the Ministry of Environmental Protection, measures are being taken to limit the public’s exposure to magnetic fields.
The main methods of limiting the level of magnetic fields are moving away from the source, which can phase, reducing the areas of magnetic loops of cables and metallic shielding. In cases where none of these methods are applicable or effective, such as in front of overhead power lines, there is a technique of actively canceling the magnetic field.
In this technique, the field that produces the PO field is flowed in large loops designed according to the structure to be protected, in its strength and direction to the field that originates from the upper voltage lines.
The connection of the fields from the power lines and the active system amounts to a magnetic field in the building and the protected area.
This solution was successfully applied for the first time in Israel since 2007 in a public building in Tel Aviv. and in large office buildings.
The article presented here will describe the main points of the method, the requirements for the system’s performance, the planning considerations and the stages of the project’s implementation, including photographs from the sites as well as the results of the measurements that confirm the effectiveness of the method.
A policy principle that justifies pre-emptive action to prevent serious or irreversible threats to human health or the environment, even in a situation of scientific uncertainty as to the nature of these threats or as to their feasibility (for example, due to the lack of knowledge about the connection between an environmental pollutant and an increase in morbidity).
The principle does not have a uniform definition accepted by all and is open to different interpretations. For example, the German interpretation of the principle focuses on reducing risks by relying on the best available technology, the official interpretation of the European Community sees the principle as a risk management tool that is used as long as scientists do not have satisfactory answers, while a radical interpretation acknowledges our ignorance in the face of the complexity of risks environmental health and promotes changes in production and consumption to prevent their creation.
Magnetic radiation limitation system, works well, in several options:
When none of these methods are applicable, there is one more option active field restriction.
The technique of actively limiting a magnetic field has existed for over a century and its invention is credited to the German physician and physicist Hermann Ludwig Helmhall, who discovered the law of conservation of energy.
The method is mainly applied to limit a magnetic field in small volumes, for example around scanning electron microscopes whose sensitivity is up to Mg 0.2.
The application to protect buildings against magnetic fields from power lines is recognized worldwide and is applied commercially, but until 2007 the method was not applied in Israel to an entire building.
The principle of the method for the protection of buildings, the special magnetic field sensors measure the field BP in the place where they are installed and transmit this information to one or more controllers, the controller commands all the signal to the amplifiers that flow current in loops (at different angles to the an- to offset the vertical and horizontal magnetic field vehicles together) They produce a BC field opposite in direction and equal in magnitude to the field from the upper voltage line, so that the field value in the sensors is minimal. In this way, there is a reduction in the constant factor of the magnetic field, while following the field changes from the upper voltage line. The reduction capacity ranges from approximately 3 to 8 times the value of the field before the active cancellation.
The cancellation system reduces the field in the desired location, but increases it outside the structure.
The method in an educational institution in North Tel Aviv. The magnetic field measured, among other things, by the Ministry of Environmental Protection in 2005 and by surveyors on behalf of the children’s parents in the kindergarten, was 8 milligauss on the front facing the street and about 4 milligauss inside the premises of the institution
The goal of the magnetic field that was required in the entire area of the garden and its playground was 3 ± 1 milligauss on average for 24 hours using the solution was to produce a canceling magnetic field. Two loops by using magnetic models based on MATLAB, BFAST software
The Dolev company examined the content considerations under conditions of extreme non-identity in the circuit currents of the upper voltage line included the calculation of the current in each of the loops, which contained a multi-core cable connected in a column with an NI hem to produce and light- the loops that affected the resistance and inductance of the loop.
From the amplifiers necessary to supply the current in each of the loops to create the canceling field were derived. The design resulted in the cancellation system performance described in fig. The actual implementation included digging trenches for underground cables while taking into account other utilities such as Bezeq, low-voltage cable bushings, and more, and installing columns for the overhead cables of the two loops for the purpose of verifying the system’s performance. An innovative monitoring system for continuous testing of the magnetic field was placed on the premises of the institution.
The magnetic sensor indication of this system, while activating the active cancellation system.
The value of the magnetic field is about 1 milligauss, a value lower than even the target value at the time of measurement. The field from the geneticist was monitored at the Notar institution for three months from the activation of the cancellation system in August 2007.
The results given at the closing of the issue (at the electrical engineers conference in Eilat) in which the systems were presented for the first time by engineer Oren Hertel and Yossi Hershkovitz from the Dolev company are that the performance of the system is better than required.
The active radiation limitation system was also implemented in a number of industrial buildings and offices in Rosh Ha’Ain, including several buildings with a width of more than 60 meters each, three stories high and a warehouse floor on the ground level separated from each other by a space for vehicle entry. The upper voltage line in front of the buildings serves as a corridor for passing electricity from west to east and to the south with a complex circuit routing structure.
The magnetic field levels near the front wall facing the upper power lines ranged from 6 milligauss in the center of the building on the middle floor to about 12 milligauss at the ends of the building.
The solution included the installation of two loops for each of the two buildings, one at a distance of about a meter from the roof of the building in the direction of the power lines and the other at a height of five meters from the level of the outdoor parking lot and at a distance of 1.5 meters from the wall of the building. The returning loops passed through the lower parking lot level.
After the systems were activated, the field was measured by a qualified tester and the results were better than required
The company Dolev Electromechanika from the Dolev Group, is the exclusive representative in Israel of the EMF company from the USA, plans, builds and maintains active cancellation systems against a magnetic field that were already activated in Israel for the first time in August 2007 at three sites and an educational institution in Tel Aviv. In the four cases, the system succeeded in significantly reducing the magnetic field That there were humans to values below the set target values of 204 milgauss, thereby proving the effectiveness of the method.
Dolev exclusive representatives of the world’s leading companies in the field of radiation limitation solutions.
The Dolev company performs radiation measurements for the shielding projects with calibrated and certified equipment.
During a visit to the first active defense project in Israel, Tel Aviv Mayor Ron Huldai and his entourage were impressed.
The mayor was impressed by the innovative system and the ability to eliminate radiation from overhead power lines of an electricity company, which pass through settlements and expose residents to dangerous levels of radiation.
