High voltage transmission lines are overhead power lines used for efficient bulk power transmission. Since the power needs to be transmitted over long distances, the voltage level of transmitted power is increased to reduce the current to minimize I²R i.e., power losses during transmission. The lower the current, the lower the resistive losses in the conductors. That's why these lines are termed as high voltage transmission lines.
Transmission lines or overhead Power Lines transmit electricity from the generating stations to other places such as large industries or to distribution networks from where the electricity is further supplied to different consumers. Step-up transformers are used at the generation end to increase the voltage level of transmission.
According to ANSI, transmission lines can be categorized based on different voltage levels as:
A Transmission tower consists of the following constructional parts:
There are a number of hazards related to high voltage power lines. Electricity can be very dangerous for surrounding. The dangers are as follows:
The concern for health hazards related to overhead power lines was first raised in 1979. In this study, it was discussed that electromagnetic radiations emitting from powerlines can cause childhood leukemia. Some researches stated that power lines can cause cancer and other critical health problems and the closer we get to HV overhead lines, the more dangerous the electromagnetic radiations become.
According to the research of the World Health Organization, we can suffer from insomnia, anxiety, headache, skin burns, fatigue, and muscle pain because of radiations from HV power lines. If such conditions really do occur, then electromagnetic radiations can be prevented from entering the human body by providing adequate shielding using metal. Things like buildings, trees, etc. can also serve as shielding for this purpose. In this way, we can reduce the health hazards caused by these dangerous radiations.
However, contrary to this belief, there are several arguments by experts stating that power lines create no such health hazards at all. In 1995 APS (American Physical Society) rejected linking childhood leukemia with power lines as there was no evidence that whether power lines caused it or rather it was just a coincidence. National Institute of Environmental Health Sciences (NIEHS) reported in 1999 that there is no such evidence to prove any health hazards of power lines nor their safety.We can conclude that there is no known health hazard related to living near HV power lines but also science has not proven power lines as completely risk free. Scientists are still doing various research over this argument to make the environment safer.
Electric shock occurs when current passes through the human body when coming in contact with an energized conductor. Damage caused by electric shock depends on the severity of the shock or can say it depends on the level of voltage of the shock. It can cause skin burns and, in some cases, can lead to internal injuries or even death.Arcing can be defined as dangerous conditions related to the release of energy due to electric arc. It occurs when accidentally a conductive object or body comes too close with the highly energized conductor causing an arc to produce at the points of contact. It can cause serious skin burns due to direct heat exposure.
Step potential is created when a fault occurs in power lines and current from the conductor starts to flow towards the earth. The voltage level of the area surrounding the grounding point is not uniform due to non-uniformity in resistivity of soil, so a potential difference is created there.
A person entering the vicinity of grounding has the difference of voltage between the two steps and thus due to potential difference current enters the body through the foot which is at higher potential and leaves through the other. This is known as step potential.Touch potential is defined as the difference in the voltage level of a person's feet and the energized equipment. If the person accidentally touches that energized body, then-current enters his body due to a potential difference.
There are some precautions which must be followed to avoid electrical hazards and risks:
Besides the precautions, there are also some safety rules for the linemen who work on HV transmission lines. These areas following:
Electricity is a great blessing for us as it has advanced and automated our life to an infinite extent. But along with these benefits, electricity is also very dangerous at the same time. It creates a number of hazards and health issues thus endangering our life. If we properly follow the safety rules, standards, and precautions, then we can reduce and even eliminate the risks and hazards caused by electricity. Conclusively, it's up to us that either we make our life comfortable or full of risks.
About The Author
Abdur Rehman is a professional electrical engineer with more than eight years of experience working with equipment from 208V to 115kV in both the Utility and Industrial & Commercial space. He has a particular focus on Power Systems Protection & Engineering Studies.