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SECTION 3.0:ELECTRIC TRANSMISSION <br /> 3.4.2 Electrical Effects <br /> The electrical effects of high-voltage transmission lines fall into two broad categories: corona <br /> effects and field effects. Corona is the ionization of the air that occurs at the surface of the <br /> energized conductor and suspension hardware due to high electric field strength at the <br /> surface of the metal during certain conditions. Corona may result in radio and television <br /> reception interference, audible noise,light, and production of ozone. Field effects are the <br /> voltages and currents that may be induced in nearby conducting objects. A transmission <br /> line's inherent electric and magnetic fields cause these effects. <br /> 3.4.2.1 Electric and Magnetic Fields <br /> Operating power lines,like the energized components of electrical motors,home wiring, <br /> lighting,and other electrical appliances,produce electric and magnetic fields,commonly <br /> referred to as electromagnetic field (EMF). The EMF produced by the alternating current <br /> electrical power system in the United States has a frequency of 60 hertz,meaning that the <br /> intensity and orientation of the field changes 60 times per second. <br /> Electric fields around transmission lines are produced by electrical charges on the energized <br /> conductor. Electric field strength is directly proportional to the line's voltage;that is, <br /> increased voltage produces a stronger electric field. At a given distance from the <br /> transmission line conductor,the electric field is inversely proportional to the distance from <br /> the conductors, so that the electric field strength declines as the distance from the conductor <br /> increases. The strength of the electric field is measured in units of kilovolts per meter. The <br /> electric field around a transmission line remains steady and is not affected by the common <br /> daily and seasonal fluctuations in usage of electricity by customers. <br /> Magnetic fields around transmission lines are produced by the level of current flow, <br /> measured in terms of amperes,through the conductors. The magnetic field strength is also <br /> directly proportional to the current;that is,increased amperes produce a stronger magnetic <br /> field. The magnetic field is inversely proportional to the distance from the conductors. Thus, <br /> like the electric field,the magnetic field strength declines as the distance from the conductor <br /> increases. Magnetic fields are expressed in units of milligauss. The amperes and,therefore <br /> the magnetic field around a transmission line,fluctuate daily and seasonally as the usage of <br /> electricity varies. <br /> Considerable research has been conducted over the last 30 years on the possible biological <br /> effects and human health effects from EMF. This research has produced many studies that <br /> offer no uniform conclusions about whether long-term exposure to EMF is harmful. In the <br /> absence of conclusive or evocative evidence, some states, California in particular,have chosen <br /> not to specify maximum acceptable levels of EMF. Instead,these states mandate a program of <br /> prudent avoidance whereby EMF exposure to the public would be minimized by <br /> encouraging electric utilities to use cost-effective techniques to reduce the levels of EMF. <br /> 3.4.2.2 Audible Noise and Radio and Television Interference <br /> Corona from a transmission line may result in the production of audible noise or radio and <br /> television interference. Corona is a function of the voltage of the line, the diameter of the <br /> conductor, and the condition of the conductor and suspension hardware. The electric field <br /> gradient is the rate at which the electric field changes and is directly related to the line voltage. <br /> SACI3713221082350006(LEC_3.0_ELECTRANS.DOC) 3-7 <br />