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Electricity in power stations is generated at 25 000 volts why is it transmitted across the National Grid system at 132 000 volts?
Voltage is stepped up to higher voltages for transmission in a power transmission system in order to reduce the current required to deliver a certain power and, as a result, to reduce the size of the conductors required. Remember that power is current times voltage, so increasing the voltage allows a reduction in current for the same amount of power. Also, remember that the size of the conductor is proportional to the amount of current alone. At the receiving substation, the transmission level voltage is stepped down to a distribution level voltage, typically in the range of 11 to 13KV. It is then stepped down to service level voltages at the local distribution transformer serving a business or a group of residences.
What does 200kb volts get reduced to when it gos through a substation?
There are at least two fundamental problems with this question. First, and assuming that the subject is electrical power transmission, the generated power will always be expressed in killovolts or "kv", which indicates "thousands of volts". The 200kb that is given is a computer expression indicating killobytes, which indicates a factor of 1,024 bytes. Second, the 200k value given in this question is not familiar. A real-world value will be closer to 230kv, and depending on the area served, this value may very well rise toward a million killovolts, or may be less. In answering the "question apparent", we can now assume that 230kv is transmitted from a power generator to a distribution network where there should be several, if not many, substations. Such a network is typically located within a large geographic area. The substations and their outputs (reduced voltages) are designed specifically to meet the needs of the area served. Some examples of output voltages are 26kv, 13kv, and 4kv.
What do pylons effect?
Powerful electromagnetic fields exist under overhead power lines. The cables carried on pylons across the countryside often have potentials of four hundred thousand volts or more. If you stand under such a line you will often be able to hear a rhythmic humming. In damp weather you can hear the crackling as some of the electricity discharges into the atmosphere.Under the more powerful lines the fields will light up a fluorescent tube when someone stands underneath the cables holding one end of the tube. ( Warning: This is a potentially dangerous trick, so you should not try it yourself!). At least one individual is on record who remembered enough school science to erect a cable strung between two poles under a power line near his home, connected the ends to his household supply and got free power until the authorities caught up with him and sued him for stealing electricity! You do not need physical connections to extract power from an electrical field.The person with the fluorescent tube standing under the power line also had electrical currents and voltages induced in his body. This happens because the blood and other body fluids conduct electricity and, as with any conductor in a moving electric field, a current will be produced in the body. You have seen how even the much lower voltages of mains cables at home will produce this phenomenon and you can demonstrate the effect using an earthed voltmeter in the way described in the last chapter. Obviously the effect will be much bigger directly under a pylon.You can alarmingly demonstrate this induction effect by parking a vehicle (the larger the better) under a power line' High static charges will build up m the metal body and because of the rubber tyres will only slowly be discharged to earth. A large spark will be produced if you reach out to touch the van.Despite these obvious anct measurable effects, the official position of the electric power companies has always been that, party tricks excepted, there is no possibility that even long-term exposure to high electromagnetic fields can have injurious effects on health.However, too many people who live in houses under or near power lines complain of a variety of symptoms without apparent cause for such assurances to be accepted without question. Some feel perpetually lacking in energy. In worse cases, they may feel nauseous or dizzy. The long-term effects remain to be assessed, but when we remember the findings of Nancy Wertheimer there appears to be at least a possibility of a link with cancer and there is current litigation in both Britain and the USA against power transmission companies which, if successful, will result in enormous damages being paid to affected families.LIVING BENEATH POWER LINESProbably the most famous mass example of illness caused by fields from power lines is that of the English (Gloucestershire) village of Fishpond, where many of the residents suffered from similar symptoms over a long period. The village had the misfortune to be effectively surrounded by several high-tension power lines, but a clear connection with the villagers' health was not made until the power line voltages were greatly increased. No-one in the village knew of this, but the incidence and severity of the symptoms increased dramatically with some people even blacking out. Measurements were taken in the village of the magnetic Field strengths in the homes of those affected. While some of the houses had quite high field levels, the houses of other people living further away from the lines, but still showing symptoms had magnetic fields of as little as ImG.A pylon Hangs Over the Village of Dalmally, ScotlandAnother case has been reported from the village of Dalmally in Argyll, Scotland, where 275kV power cables pass over a council house estate, the police station, post office and within 100 metres of the school. In the estate of thirty-six houses, eight people died from cancer over a five year period, and a further three residents of the tiny village died from motor neurone disease. The council built the houses around the existing pylons and so close to them that engineers had to cut back small trees and shrubs in one garden to avoid current earthing through them. Thunderstorms caused especial havoc in that same garden, with sparks flashing to earth, terrifying dogs and the owner, who at the time of writing is confined to a wheelchair, suffering from a severe unspecified myalgic illness.When the houses were built in 1977 no-one realised the connection between high-tension cables and illness, but even so, the buzzing and crackling from the cables, even on a dry day, is disconcerting. The incongruity of such a massive high-tension pylon in a crowded road is further highlighted when you look around at the wild Highland scenery, as the nearest hamlet is 18 kilometres away! It may be that the power lines are only partly to blame in this case, as David Cowan found when he investigated a case of M. E. about 150 metres from the lines. A stream runs down the back of the village and at least one line of geopathic energy passes under the affected house, causing unhealthy spirals (see Chapter 15).Many people exposed to high voltage fields from power lines suffer the types of stress-related complaints we have discussed earlier. Some develop even more severe symptoms of stress, leading to depression or even a suicidal frame of mind, as was shown by the research of Dr. Perry and Dr. Dowson referred to in Chapter 1. There are those whose asthma and other allergic reactions can be linked to proximity to power lines. Doctors specialising in clinical ecology often find that exposure to electromagnetic fields provides a crucial trigger factor in the onset of attacks.Animals can also suffer from adverse reactions to high-tension lines and their response helps to scotch any suggestion that what we are seeing in cases like those described is merely psychosomatic. A three part television series shown originally on British Channel 4 in 1984 and repeated since: "The Good, the Bad, and the Indefensible", illustrated the plight of an American farmer across whose land a massive power line was erected. Shortly after its installation, his hens started to lay 'scrambled' eggs, his cattle aborted and their milk production fell drastically. These results echoed laboratory experiments (referred to elsewhere) in which eggs and mice suffered ill effects when exposed to various types and strengths of magnetic and electrical fields.THE CANCER CONNECTIONMention was made in Chapter 1 of how the American researcher Nancy Wertheimer, during her research into childhood leukaemia 20 years ago, first identified the possibility of a link between power lines and cancer. It has to be said that when she started she had no thought of power supplies being involved. She was investigating the hypothesis that the answer lay in conventional environmental or infectious factors.However, examination of her data eventually led her to the puzzling rinding that children living in two houses nearest to the power poles that carried transformers (where the voltage was stepped down from 13kV to the American domestic 120 volts) showed the highest incidence of the disease. Further investigation showed that the crucial factor was not the proximity to the transformers and the fields that they radiated, but the current carried in the distribution lines. This in turn directly determined the strength of the magnetic field generated by them. Because of the configuration of the distribution system, the field strength fell off sharply immediately beyond the second house from the transformer.Wertheimer, together with another researcher called Ed Leeper, carried out further detailed analysis of the results as well as some more epidemiological studies, all of which supported the idea of a link with magnetic field strengths. The results were finally published in 1979.Several later investigations including work by Becker, Marino and Savitz in the U.S.A. and Tomenius in Sweden, have supported Wertheimer's findings. Until recently, the medical profession and the electric power companies have stubbornly refused to admit that electromagnetic fields could produce carcinogenic conditions and have generally rejected the research. There have, however, been some notable court cases in America that have, for example, led to the very expensive re-routing of a power line built near a school and to several claims for damages.While it is clear that American researchers have led the way, notably with the New York State power lines project headed by Savitz, UK power companies have undertaken a number of research projects and it appears that some more serious investigation is now under way, even though this is still being done very discreetly and with, as yet, little evidence of a changed attitude. The official position remains stuck somewhere between scepticism and hostility, but there are signs that policies are quietly changing. Lofty dismissals of any suggestion that there may be a link are beginning to give way to more cautious reactions. New lines are being routed further away from dwellings than would previously have been the case, and enquiries from concerned members of the public are often treated with much more understanding and tolerance. Some recent planning decisions in the UK have gone against building near or under power lines.None of this should lead anyone to conclude that the case is officially conceded. Nevertheless, over the last few years there has certainly been a marked change of attitude. A court case underway at the time of writing illustrates the increased level of public awareness which has doubtless contributed to such changes. The Studholmes, a family in the Manchester area in England, have finally been awarded Legal Aid to sue the local electricity company over the death of their 13-year old son Simon from leukaemia. The family home was near to 660kV power lines. He had slept with his head near to the electricity meter. An electricity sub-station was outside the room and two cables from it ran under the drive of the house. The same power lines run directly over a nearby pub, called The Sparking Clog' (producing fields 24 times the recommended Swedish limits) and the landlady complained of headaches and other illness which disappeared when she spent time away from the pub.1Conversely, someone living 100 or 150ft from a high-tension power distribution line may not experience very strong fields. At these distances, the fields may often be only a few milli-gauss and thus much weaker than those from a hand-held domestic appliance, but it is again the question of length of exposure that is crucial. A hair dryer will commonly generate a 300-400mG magnetic field in the brain, but only for 5 minutes a few times a week. A power line (at 100 feet away, or more) may produce a more or less uniform field of barely 3mG in a house, but this will result in a magnetic 'dose' several times higher than that from the hair dryer for someone spending most of their time at home. Even more important, this level of background exposure will continue throughout the crucial sleeping hours.Of course, a great many people live much closer to power lines than that. Indeed, if the line is a 400-600KV one carrying high currents, the fields produced by it will be many times higher than in our example.AVOIDING THE PROBLEMThe only sensible advice for someone living close enough to a power line to be affected is to move, particularly if there are young children at home. Whether the symptoms felt are those that have been attributed to electro-stress or the much more worrying possibility of carcinogenic effects, even if they have not been officially 'proven', it is still wise to move.Only constant public challenging of the electricity companies and the government will bring about a change of attitude. We may then see regulations compelling the siting of power lines routed away from existing residential areas and builders no longer able to put houses within high risk zones. Planning blight and legal action are both possible consequences of a change of policy, not to mention severe effects on the market value of houses already situated unfavourably. On the other hand, it seems to be increasingly clear that lives are at risk in the meantime.A further concern is that electricity companies are known to be keen to develop super-conducting cables. The attraction is obvious as the resistance of any normal cable leads to significant loss of power. This is greater the higher the voltage carried and the further the distance the electricity travels. Not only would super-conductor cables cut these losses, they would also make it possible to carry even higher voltages. Unfortunately, this would mean yet more powerful fields surrounding the transmission lines, increasing the width of the blighted corridor along each line of pylons.Safe corridors around lines in many countries are still a hope rather than fact. With so many dwellings and other buildings already far too close to lines anyway, the potential for many hundreds of Fishponds-like incidents (but of a much greater magnitude) is clear. Legislation of the type discussed later is a matter of extreme urgency.Note:1 Foster, J., The Independent, (22 January, 1994) Page 9.Return to Book "Safe As Houses"Return to Home Page
