When the human body touches conductive parts with different potentials at the same time, the potential difference causes current to flow through the human body, which is called electrical contact. Depending on the size and duration of the contact current, it has different effects on the human body. Small electric currents are harmless to the human body. Some medical electrical equipment used for diagnosis and treatment can cure diseases and save lives through trace amounts of current when in contact with the human body, which is beneficial to the human body. This kind of electrical contact is called micro-electrical contact. If the current passing through the human body is large and lasts for too long, the person may be injured or even killed. This kind of electrical contact is called electric shock. Electric shock is life-threatening, so electrical professionals should understand the effects of electric current passing through the human body in order to take correct and effective preventive measures to avoid electric shock accidents.
Sensory threshold - the minimum current value that the human body can feel, generally 0.5mA. This value has nothing to do with the duration of current passing.
Escape threshold - when a person holds a charged conductor with his hand, if the current flowing through the palm exceeds this value, the muscle response will be to cling to the charged conductor unsatisfactorily instead of getting rid of the charged conductor, thus causing Electric current can continue to pass through the body. The minimum current that causes this effect is called the escape threshold. This value varies from person to person. The IEC takes the average value as 10mA. If you cannot get rid of the charged conductor, the human body will be injured or even killed under the action of large current for a long time. When other parts of the human body come into contact with a live conductor, it can escape from the live conductor instantly. There is no danger of death from electric shock, but it may cause secondary injuries, such as casualties caused by falling to the ground from a height due to electric shock.
Ventricular fibrillation threshold - Ventricular fibrillation caused by electric current passing through the human body is the main cause of death by electric shock. The minimum current that causes ventricular fibrillation is called ventricular fibrillation (hereinafter referred to as ventricular fibrillation). tremor) threshold. This threshold is related to the length of time the electricity is on, as well as to the human body's condition, heart function, and the path that the current passes through the human body, but it has nothing to do with the person's gender, skin color, or race. According to the IEC 60479 standard, the relationship between the 15-100Hz AC current Ie passing through the human body and the energization time t, which causes ventricular fibrillation, is shown in Figure 1-1, curve e.