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Ecological & Biological Effects of High Voltage Powerlines

By Ashish Sinha

Whenever the need arises for planning & designing a high voltage transmission line there are various factors, which are, be taken into accounts. For e.g. Stability, Reliability, Losses, Economics, Environmental impact etc. Here is the seminar I shall be restricting myself to the environmental impact only. In future this factor is going to play key role during the design of electrical system. Our country has a very high population density & since it is now changing over to the next generation of transmission voltage with 800 kV power lines, there will be various effects like Ecological & Biological, due to these power lines. Hence this Electrical Engg field should be given full attention. Environmental impact includes the effect of Audio, radio & Television interference, effect of electric & Magnetic fields on plants, animals and human beings & on many other objects. We shall deal with them one by one.

Effects of Electric field due to HVPL

Electrostatic field may cause unpleasant sensation such as skin sparking, hair attraction, depending upon time of Exposure of the human body to high intensity electric field, physiological changes may occur on a long term basis providing disorders in cardiac, thermoregulation, heart beat & arterial pressure. It is also seen that visual reaction time is increased, memory decreases, disturbance in CNS occurs. And some cases of damage of Chromosomes are also reported. Birth defects in Children of Parents exposed to electric field were 10 % against 2.1 % to that of parents unexposed to electric field. These are the direct effects of HVPL. In addition, exposure of objects like vehicles, fences, rain gutter, antenna, umbrella etc. to electric field, result in stored electrostatic energy which in contact with human beings is discharged in the form of electric current. This current depending upon its intensity may vary from light shock sensation or even ventricular fibrillation causing cardiac arrest. Japanese observers indicate that above 3 k V/m of electric field Strength, people carrying umbrella may get unpleasant sensation while touching the metal parts of umbrella. If we assume that the human body offers pure resistance of 2k ohms to discharge currents the limit of undistributed field for human beings to experience shock is 15 kV/m. Under an outer phase of 800 kV line, current in various points of the human body are Neck : 0.157 mA Waist : 0.149 mA Knee : 0.182 mA Ankle : 0.194 mA


Induced Current/Voltages or Touch Currents

For alternating Current transmission the electric field between ground & conductor is associated with surface charges, which sinusoidal varies with time. The magnitude of internal current is proportional to the displacement current density & object size, shape & position. For a person in a field of 10 kV/m, internal current lies between 100 to 200 micro amp, these are well below threshold of perception. However the alternating charges induced on the skin, hair or clothes are acted on by electric fields to produce mechanical force. There will be also forces on static charges that the body may have accumulated. These cause tingling sensation in people standing near an AC field. Also the voltage gradients within the body are less than those outside, being determined by current density and Impedance (largely reactive) of tissues. The internal gradients of 10 to 20 m V/m would results in internal voltage drop (head to toe) of few tens of million volts. Relatively large p.d. however appears between the grounds or between body and other object if the body is not in good electrical contact with the ground, body current may flow via that object instead of taking normal path through feet & shoe. This can occur while holding a metal-shafted walking stick. The human body itself may provide path to ground for all charging induced on objects such as vehicles, antennas, and fences having high degree of insulation to the ground. The effect of electric field is not less pronounced on animal life. Exposure of rats to 5k V/m of electric field at 50 Hz for 10 days gave the following results. Process of stimulation in CNS was affected Increae in reflex latency Increase in blood glucose. Decrease in liver glycogen Changes in Brain mitochondrion Thyroid functions were affected Increase in estrous cycle & gestational periods in mice Decrease in growth rate. Electrostatic field of about 30 k V/m affects pigeons & hens. They are unable to pick up grains because of chattering of their beaks. Which in turn affect their growth. Other animals get a charge on their bodies. When they proceed towards water pool a spark usually jumps from their nose to the grounded pool.


Effects of HVPL on Plant Life

Plants such as wheat, rice, sugarcane etc suffers the following damages. At 20 k V/m the sharp edges of the stalks gives corona discharges so that the damages occurs to the grain bearing plant. At 30 k V/m the by-product of Ozone & NO become intense. The resistance heating due to increased current prevents full growth of the plants and grains. Probability of burning of trees increases. The electric field due to 800 kV line at 6m below is sufficient to burn the trees. Fences, buried cables & pipelines require careful layout. Laying of Pipeline longer than 75 km & larger than 15-cm diameters are recommended to be at least 30 m laterally from line center to avoid dangerous eddy currents that could cause corrosion. The degree of Ozone emanation & tissue damage is also present. Tube light rode glows when taken under 400 kV transmission line So what about electrons in your body?


Theory behind these effects

Ion Cyclotron Resonance (ICR) is a process, which occurs & is responsible for various changes in the body. Current passes through membranes of the tissues, which can be regarded as excellent conductors. Ions of K, Ca, Li, Mg are disturbed as they resonate thus affecting the body activity. Induced current in the body circulates primarily via the vascular network of the low resistance of blood & that is stimulates the CNS & alters biochem reactions.

Effect of Magnetic Field

Magnetic field exposure on human health can cause Chilhood cancer Leukimia & other cancer Inteference with cardiac pacemaker Damage to developing embryonic system Effects cellular process


According to World Health Organization (WHO)

Above 60 mT at 50 Hz hazards are possible. Alternations in cells, tissues & other system etc. have been reported above 5m T. An experiment was conducted at Texas University in which some cancer cells were placed in magnetic & electric field for 24 hours. The result was that the cancer cells were growing at a rate, which was 24 times their normal growth rate. And white blood cells were also ineffective on these cancer cells. Melatonin is a hormone produced in pinial gland in brain & is capable of destroying cancer cells. In an experiment at Pacific Northwest laboratory, it was found that the percent of Melatonin was decreased by 40 % in person living near 765kV power line.

Max Exposure Time for Human beings under