The degree of harm to the human body from electric shock depends mainly on the size of the current through the body and the duration of the energization. The greater the intensity of the current, the greater the risk of fatal; the longer the duration, the greater the possibility of death. Can cause people to feel the smallest value of the current known as the perception of the current, AC 1mA, DC 5mA; people can get rid of their own current after electrocution is called the maximum current to get rid of the current, AC 10mA, DC 50mA; in a relatively short period of time life-threatening current known as the fatal current, such as 100mA current through the human body for 1s, can be enough to make the person fatal, and therefore the fatal current is 50mA. Prevent electric shock protection device, the human body is allowed to pass the current can generally be considered as 30mA.
The human body's reaction to the current:
8~10mA hand off the electrode has been difficult, there is a sharp pain (finger joints).
20~25mA The hand is quickly paralyzed, can not automatically get rid of the electrode, breathing difficulties.
50~80mA Dyspnea, atrial fibrillation.
90~100mA Respiratory paralysis, three seconds after the heart began to paralyze, stop beating.
According to Ohm's law (I = U / R) can be known that the size of the current flowing through the human body and the applied voltage and human resistance. Human body resistance in addition to their own resistance, should be attached to the human body outside the clothes, shoes, pants and other resistance, although the human body resistance is generally up to 5000 Ω, however, the impact of the human body resistance of a number of factors, such as wet skin sweating, with conductive dust, increase the contact area with the electrically charged body and the pressure as well as clothing, shoes, socks, wet oil and so on, are able to reduce the resistance of the human body, so the human body is usually flowing through the human body The size of the current cannot be calculated in advance. Therefore, in order to determine the safety conditions, often do not use the safety current, but the safety voltage to estimate: in general, that is, dry and electrocution risk is greater under the environment, the safety voltage is stipulated as 36V, for the wet and electrocution risk is greater in the environment (such as metal containers, pipeline welding maintenance), the safety voltage is stipulated as 12V, so that the electrocution of the current through the human body can be limited to a small range, can be in the range of 12V, the current through the human body can be limited to a small range. In a smaller range, to a certain extent, to protect personal safety