The so-called step voltage refers to the voltage between the feet of a person walking in the potential distribution area around the grounding current entry point when an electrical equipment undergoes a grounding fault.
When a live wire of an overhead line breaks and falls to the ground, the potential of the landing point is the same as that of the live wire, and the current will flow from the landing point of the wire to the ground. Therefore, a potential distribution area is formed on the ground centered around the landing point of the wire. The farther away from the landing point, the more dispersed the current is, and the lower the ground potential. If people or livestock stand within 8-10 meters from the landing point of the power line, an electric shock accident may occur, which is called step voltage electric shock.
When a person is subjected to step voltage, although the current flows along the person's lower body, from the feet to the legs, crotch, and feet, forming a pathway with the earth without passing through important organs of the human body, it may seem safer, but in reality it is not!
Because when a person is subjected to a high step voltage, their feet will cramp, causing their body to fall to the ground. This not only increases the current acting on the body, but also changes the path of the current passing through the human body, potentially flowing through important organs such as head to hand or feet. Experience has shown that if an electric current continues to act in the body for 2 seconds after a person falls, this type of electric shock can be fatal.
The magnitude of step voltage depends on the distance between the human body and the grounding point. The farther the distance, the smaller the step voltage value. At a distance of 20 meters away from the grounding point, the potential is approximately zero. The closer to the grounding point, the higher the step voltage.