pole with wires overhead power lines have become so commonplace attribute the landscape of the modern world that many simply do not notice them.Despite the high location of the conductors to prevent accidental touch, they are, nevertheless, fraught with potential danger.Everyone remembers the situation of childhood, when parents saw a broken wire lying on the ground, trying to get around this place, "the tenth road."This prevents electric shock as step voltage decreases with the distance.We all know that we can not approach the broken wires.However, what the step voltage is known only to people with electrical engineering.This article will try to find out more on this issue, explaining, literally, "on his fingers."
So, step voltage - a voltage difference between the legs, or what is also true between two (or more) points, spaced from one another at a distance of a step.In the explanation of many processes in electronics often use the analogy of water.Indeed, in some cases, the comparison of electric current and the water is quite acceptable as simplifying the understanding of the processes.So we proceed.
imagine that one of the pillars of the power line broke and one end fell to the ground with live wires.If the wire - a trumpet, and the current - water, in place of contact with the ground will be a puddle.Its diameter is spreading zone in which a person can get your feet wet.A puddle formed because water can not absorb all instantly into the soil.The size of the zone of spreading depends on the amount of water passing through a pipe per unit time.
Now back to electricity.The voltage source generates a potential difference between two points on the line, and the higher the voltage and RMS current, the greater the danger zone around the dangling wires.The emergence of "puddles" due to the high ohmic resistance of the soil: the ground loop current (according to the SAE 4 ohms) area spreading is minimal or absent.
imagine that near the broken wire is a man.Due to the distance between the feet, there is a potential difference.And because of the resistance of the body - and an electric current.In fact, it means getting electric shock.And if, after the shock a person falls (in full or in his hand), it only exacerbates the situation, as the step voltage increases.Also, if the vertical position of the body, current flows along the contour "leg - foot," that formed after the fall of other chains that can pass through the heart, posing a direct threat to life.It is easy to see that the animals (cows, bears, horses), trapped in the zone of current spreading, are at greater risk than people because they have a distance between the front and hind legs longer, and therefore more dangerous step voltage.
From all this we can draw a few conclusions:
- in contact with the zone of the current from the broken wire (or other fault) shall in no case be to panic and run.When running the distance between the base becomes larger than step, respectively, the capacity increases.Moreover, as one tries to move away from the current source, the voltage step becomes even more dangerous;
- form spreading zone can be different from the circle of the differences of the soil conductivity.
Go out of range of the step voltage can be of non-conductive materials (for example, thick dry board);hopping on one foot (in this case, no potential difference);or slow to leave, folded feet together.