Extremely Low Frequency Magnetic Fields in Electrical Substations and Residential Areas of Mangaung Metropolitan Municipality

Abstract

Since the beginning of the twenty first century electricity has become an integral part of every human‟s life. Without electricity some of the human activities on planet earth would have never been brought into existence and some of them will not be possible (Fews, 1999). Electricity is supplied to old and current technology apparatus such as computers, different types of machinery, laboratory and medical devices, household appliances, automobiles, and treatment plant equipment. Electricity moves from power generation plants (power stations) in a form of high voltage to urban and rural electrical substations where it will be converted into low voltage to suit residential electrical processes (Ilonen, 2008). According to Kaune (1993), high voltage electricity moves through overhead and underground power lines and it is converted into low voltage once it reaches electrical distribution substations in the residential areas. Furthermore, electrical substations serve many functions, such as controlling, collecting and transferring power on electrical systems (Kaune, 1993). Along the transportation and conversion of voltages, the two invisible fields known as magnetic and electric fields are produced (Kovetz, 2000). Both magnetic and electric fields are produced by movement of charged and stationary electrical particles as described in the Maxwell‟s equation (Lee, 1996). These fields are expressed in hertz (Hz) and can be classified as very low frequency (VLF), low frequency (LF), extremely low frequency (ELF) and high frequency fields (HFF) (Brent, 1999). Extremely low frequency (ELF) magnetic fields are fields with frequency that ranges between 3 to 3000 Hz and they are usually formed when the electrical current flows (World Health Organisation, 2007). According to Sinatra (2002), once there is higher current flow during conversion or transmission, high voltages are produced as a result of increased magnetic field flux. High voltages are mainly used when transferring power over long distances from generation plants to final distribution substations (Portier and Wolfe, 1998). When electricity is being transferred and has reached distribution substations, the intensity of the electric and magnetic fields changes. Lacy-Hulbert, Metcalfe and Hesketh (1998) indicated that an intensity of electric fields created is determined by the amount of voltages transferred and the flow of current determines the magnitude of magnetic fields that will be produced. The force of both magnetic and electric fields is induced by different substation devices which include wirings, cables and installations. According to the National Institute for Environmental Health (NIEH) (2002), most substations use alternating current (AC) in distributing and converting current, which produces magnetic and electric fields at various magnitude levels. The level of exposure to magnetic fields is determined by the distance between the source and the receiver (Portier and Wolfe, 1998). According to Loomis and Savitz (1995), individuals in close proximity to distribution substations are more likely to be exposed to high levels of magnetic fields than those residing far from them. Individuals exposed to magnetic fields are likely to develop detrimental health effects, such as childhood leukaemia. However there is still controversy on this matter (Draper, 2005).