Electric Grids – Introduction
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Using electricity has become part of our daily lives. We cannot imagine modern life without electricity. The production of electricity and its various applications began at the end of the 19th century, from 1882. At first, production and supply were through direct current, but use was limited because the supply was restricted to short distances (due to energy loss) and it became necessary to adapt the energy supply to different current intensities, in accordance with the needs of the end users (factories, residential consumption, etc.). Subsequently the development of alternating and multiphase currents enabled greater control and efficient use of the electric current supplied, and its distribution over greater distances. This invention in fact enabled the use of electricity throughout the whole world with uniform standards, in effect to this day. |
Electric Power Transmission Lines |
Electromagnetic fields, electric and magnetic fields, at power frequencies, exist wherever electric current flows (power lines, cables, domestic wiring, various electrical appliances, and any infrastructure or apparatus connected to the alternating electric current). These fields are of extremely low frequencies, hence their name – ELF.
Scientific evaluations regarding established hazardous effects of exposure to these fields form the basis for formulating policy on this issue, and for international recommendations regarding recommended exposure limits . These scientific evaluations focus mainly on the short-term effects of a flowing electric currents on biological systems (i.e. short term exposure to strong magnetic fields), or acute effects, for which solid scientific knowledge exists. External magnetic fields give rise to electric fields and induced currents in the body that, at high intensities, may cause neurological or muscular stimulation, and alter the level of sensitivity of nerve cells in the central nervous system.
It is important to note that besides the studies to investigate short-term effects, other studies investigate long-term chronic effects of exposure to lower levels of electromagnetic fields encountered in our daily lives. Accompanying these studies there is an ongoing public debate regarding the exposure limits, in view of the long-term potential effects, especially on the issue of the possible connection between exposure to low frequency magnetic fields and the risk of developing childhood leukemia. This debate is essential, because exposure to these frequencies is relevant to the general public in daily life.
Most countries in Europe base their policies, to one degree or another, on the recommendations of the International Council for Non-Ionizing Radiation Protection – ICNIRP However, some countries define their threshold levels based on independent evaluations of the scientific evidence and additional considerations specific to their countries, such as cost-benefit, public concern, and other social aspects. Israel is one of these countries. It was decided that the policy for determining exposure thresholds for power frequencies would be based, among other considerations, on the classification of magnetic fields at these frequencies as 'possibly carcinogenic to humans'.
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T0 be inserted here: Policies on this issue in Israel and world-wide
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References
- Basic Electricity (Dover Books on Electrical Engineering), Bureau of Naval Personnel, ISBN-13: 978-0486209739, 2nd edition, June 1, 1970
