What is the step voltage?

Poles with overhead power lineshave become so familiar attribute of the landscape of the modern world that many simply do not notice them. Despite the high location of the conductors, which prevent accidental contact, they still pose a potential danger. Everyone remembers the situation from childhood, when parents, seeing such a torn wire lying on the ground, tried to get around this place “the tenth road”. This avoids electrical injury, as the step voltage decreases with distance. We all know that we can not approach the broken wire. However, such step voltage is known only to people with electrical education. In the article we will try to understand this issue in more detail, explaining, literally, “on the fingers”.

So, step voltage is the differencepotentials between the legs or, which is also true, between two (or more) points located one from another at a distance of a step. In explaining many of the processes in electrical engineering, the analogy with water is often resorted to. Indeed, in some cases, the comparison of electric current and water is quite acceptable, as it simplifies the understanding of the processes taking place. So do.

Imagine that on one of the pillars of the linethe power line broke off and at one end fell the ground wire. If the wire is a pipe, and the current is water, then a puddle will appear at the point of contact with the ground. Its diameter is a spreading zone in which a person can wet their feet. A puddle is formed because water cannot be completely absorbed into the soil. The size of the spreading zone depends on the amount of water passing through the pipe per unit of time.

Now back to electricity. The voltage source creates a potential difference between two points of the line, and, the higher the voltage and the effective current value, the wider the danger zone around the broken wire. The appearance of the “puddle” is due to the high ohmic resistance of the soil: with a valid grounding circuit (according to the EMP 4 ohms), the spreading zone is minimal or completely absent.

Imagine that next to a broken wire isperson. Due to the distance between the feet, a potential difference appears. And because of the presence of resistance of the body - and the electric current. In fact, this means getting an electric shock. Moreover, if after a electric shock a person falls (completely or at hand), then this only aggravates the situation, as the step voltage increases. In addition, if with the body in a vertical position, the current flows along the leg-leg contour, then after the fall, other chains are formed that can pass through the heart, representing an immediate danger to life. It is easy to understand that animals (cows, bears, horses) that have fallen into the zone of current spreading are in greater danger than humans, since they have a greater distance between their front and hind legs, which means that step voltage is much more dangerous.

From all this we can draw several conclusions:

• at hit in an area of ​​action of current from danglingwires (or other malfunction) in no case can not panic and run. When running, the distance between the soles becomes larger than with the step, respectively, the potential increases. Moreover, since the person tries to move away from the current source, the step voltage becomes even more dangerous;
• the shape of the spreading zone may differ from the circle due to differences in soil conductivity.

You can leave the step voltage rangeon non-conductive material (for example, a thick dry board); jumping on one leg (in this case there is no potential difference); or go slowly, folding your feet together.