Electricity Transmission
5 min read
is transmitted from plants to end consumers via an extensive grid of overhead or underground power lines. Cables are still the only means of transporting electricity: cables supported by insulators and pylons for overhead lines, and insulated and ducted cables for underground lines.
© EDF / ROUX LIONEL - Electricity is transmitted over extremely long distances using extra-high voltage power lines. Shown here is the Baixas station, located at the France-Spain interconnection.
After leaving the power plant where it is produced, electricity first flows through the high and extra-high voltage transmission grid (HV/EHV). Most of the power lines are overhead. However, although the solution is more expensive, an increasing number of power lines especially for high voltage are being buried underground for greater safety and less energy loss.
The electricity then enters the medium and low voltage distribution grid, which delivers power over shorter distances to end consumers. A number of components ensure a safe and secure flow of electricity at this point. These include:
- Substations, where incoming high voltage is transformed to a lower voltage for distribution1.
- In these substations, circuit breakers, which protect the grid against overloading due to lightning, a short circuit caused by a tree branch, etc., by interrupting the power supply to certain faulty sections of the power line.
Are High Voltage Power Lines Hazardous?
High and extra-high voltage power lines create powerful electromagnetic fields (EMF). Extensive research on the possible effects on the health of people living near power lines and the environment has been carried out through the International EMF Project, launched by the World Health Organization (WHO) in 1996. This research2 has shown that "at a distance of between 50 to 100 meters, the strength of EMF drops off to around the levels measured in areas far away from high voltage power lines." However, the WHO has also identified some "gaps in knowledge" about EMF. Pending further scientific research on the subject, international guidelines for limiting EMF exposure have been drawn up. They take into account the occupation and age of exposed persons and the amount of time they spend close to high voltage power lines.
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