How much is the safe voltage of the human body below how many V electric days?

The voltage of the human body without any protective equipment and without any protective measures, and is in direct contact with a charged body, without any harm to the human body, is called a safe voltage. The safe voltage value depends on the resistance value of the human body and the value of the current that the human body allows to pass. In a normal environment, the average resistance of the human body is above 1K.

When the human body is in a humid environment, sweating, the voltage it withstands increases, and the resistance value of the human body decreases sharply. China stipulates the rated value of the safety voltage of 42V, 36V, 24V, 12V and 6V in the effective value of power frequency. The selection of the safety voltage value of electrical equipment should be based on factors such as the use environment, use mode and staff condition.

For example, portable lights and portable power tools can use a rated working voltage of 42V or 36V; If there is a large area of grounding conductor in a humid and narrow tunnel or mine with a humid working environment, electrical equipment with a rated voltage of 24V or 12V should be used. In addition to the independent power supply, the input circuit and the output circuit of the power supply must be isolated from the power supply of the safety voltage. Circuits operating at safe voltages must be electrically isolated from other electrical systems and any unrelated conductive parts.

According to Ohm's law, the higher the voltage, the greater the current. Thus, the voltage that may be added to the human body can be limited to a certain range, so that the current passing through the human body does not exceed the permissible range at this voltage. This voltage is called the safe voltage, also known as the safe extra low voltage.

It should be noted that under no circumstances should the safe voltage be understood as a voltage that is absolutely free of danger. Devices with a safe voltage belong to the category of equipment. 1 Safety Voltage Limit The limit is the maximum voltage value that is impossible for any two conductors under any operating condition.

China's standard stipulates that the limit of the effective value of power frequency voltage is 50V, and the limit of DC voltage is 120V. Under normal circumstances, the allowable current of the human body can be considered as the current of getting rid of; In the case of a quick-break protection device to prevent electric shock, the allowable current of the human body can be considered as 30mA. China stipulates that the limit of power frequency voltage 50V is determined according to the conditions of the allowable current of the human body of 30mA and the resistance of the human body of 1700.

China's standard also recommends: when the contact area is greater than 1cm2 and the contact time is more than 1s, the limit of the effective value of power frequency voltage in the dry environment is 33V, and the DC voltage limit is 70V; In humid environments, the effective value of power frequency voltage is limited to 16V and DC voltage to 35V. 2 Safety voltage rating The rated value of power frequency effective value in China is 42V, 36V, 24V, 12V and 6V.

Yin Zhi power tools used in particularly hazardous environments should use a safe voltage of 42V; Hand-held lights and spot lights used in environments with a risk of electric shock should use a safe voltage of 36V or 24V; Hand-held lights used in particularly dangerous environments such as metal containers and particularly humid places should use a safe voltage of 12V; Underwater operations and other places should use a safe voltage of 6V. When the electrical equipment uses a safe voltage of more than 24V, it is necessary to take protective measures against direct contact with electric shock.

A voltage below 36 volts is a safe voltage.

The safe voltage of the human body is not higher than 36V, continuous contact with the safety voltage of 24V, the safety current of 10mA, the degree of harm to the human body of electric shock, mainly depends on the size of the current through the human body and the length of the power on time.

The greater the current intensity, the greater the fatal danger; The longer it lasts, the more likely it is to die. The minimum value of current that can be perceived by a person is called the perceived current, which is 1 mA for AC and 5 mA for DC; The maximum current that a person can get rid of after an electric shock is called getting rid of the current, which is 10mA for AC and 50mA for DC; An electric current that is life-threatening for a shorter period of time is called a lethal current, and a lethal current is 50mA.

The hazard of direct electric shock.

Electric shock refers to the pathological and physiological effects caused by the passage of electric current through the human body, and electric shock is divided into two forms of injury: electric injury and electric shock. Electrical injury refers to the damage of electric current to the surface of the human body, which often does not endanger life; Electric shock refers to the direct damage to internal tissues caused by electric current through the inside of the human body, which is a dangerous injury and often leads to serious consequences, and electric shock can be divided into direct contact electric shock and indirect contact electric shock.

Direct contact shock is an electric shock suffered by a person in direct contact with a live part of an electrical device or electrical wiring. It is characterized by the human body contact voltage, that is, the voltage of the charged body touched by the person; The grounding fault current formed by the live body touched by the human body is the electric shock current of the human body. Direct contact with electric shocks is the most serious, and the resulting electrocution current is always much greater than the limit current that can cause ventricular fibrillation.

The state stipulates that the safe voltage is 36V, which is calculated according to the resistance of the human body of the general population (generally greater than 1K), and practice has proved that the human heart can cause death by passing the current of more than 40mA, U=I*R, so if the resistance is particularly small, 36V will also electrocute him.

The body's response to electric current:

8 10mA The hand has difficulty getting rid of the electrodes, and there is a sharp pain (finger joints)20 25mA The hand is quickly numb, cannot get rid of the electrodes automatically, and it is difficult to breathe.

50 80mA is difficult to breathe, and the atria begin to tremble.

90 100mA respiratory paralysis, after three seconds the heart begins to paralyze and stops beating.

Generally, for the human body, the safe voltage is below 36 volts, so more than 36 volts may be harmful to the human body.

The voltage is also known as the potential difference.

General human body safety voltage.

In order not to be higher than 36 volts, more than 36 volts may be harmful to the human body, and the degree of harm to the human body by voltage mainly depends on the size of the current through the human body, the length of the energizing time, and the current intensity.

The greater the danger, the greater the fatal danger and even death.

Behavior of the human body when electrocuted:When the injury of the electrocuted person is mild, he is often more conscious, and only palpitation, numbness of the limbs, general weakness and other manifestations will occur, and sometimes after the electric shock, it may cause the patient to have local electrical burns, and when the injury is more serious, it may make the electrocuted person lose consciousness and dilate the pupils.

Pale complexion can even cause the patient's pulse and breathing to stop.

1. Allowable current in the human body.

In the range of getting rid of the current, the human body can get rid of the charged body and remove the risk of electric shock after the electric shock, therefore, in general, the removal of the current can be regarded as the allowable current of the human body In the case of a protective device (security device) to prevent electric shock, the current allowed by the human body can be considered as 30mA In the air, water surface and other occasions that may cause serious secondary accidents due to electric shock, the allowable current of the human body should be considered as 5mA that does not cause strong spasms

It should be emphasized that the allowable current of the human body mentioned here does not refer to the current value that the human body can withstand for a long time (for the smallest current that can cause human sensations but cannot withstand for a long time, that is, the perceived current, the average adult male is about 11mA, and the adult female is about It can be seen that under certain conditions, the allowable current of the human body cannot exceed 30mA, and it will be smaller in some special occasions

2. Human body resistance.

The resistance of the human body is mainly composed of internal resistance, resistance and capacitance The capacitance of the body is small and negligible

The internal resistance is basically not affected by external factors, and its resistance value is about 500

**The resistance changes in a wide range with different conditions, so that the total resistance of the human body also varies in a wide range **The resistance of the thick stratum corneum on the surface is as high as 10000 100000, but the stratum corneum is not a complete film, and it is easy to be destroyed It should not be taken into account when calculating the resistance of the human body To remove the stratum corneum, the resistance of the human body is generally not less than 1000

In addition to the thickness of the human body, the factors that affect the resistance of the human body will reduce the resistance of the human body due to moisture, sweating, damage, and charged dust; The increase of the contact area and the increase of the contact pressure will also reduce the resistance of the human body; By increasing the current, the energizing time will increase, sweating and heating will also reduce the resistance of the human body; The increased contact voltage will break through the stratum corneum, and the enhancement of the body's electrolysis will also reduce the body's electrical resistance

Considering the above many factors, in general, the resistance of the human body can be considered as 1000 2000

3. Safety voltage value.

China's safety voltage mostly uses 36V This regulation is based on the product of the allowable current of the human body and the resistance of the human body, 36V is roughly equivalent to the allowable current of the human body 30mA, and the resistance of the human body is 1200, that is, it is roughly equivalent to the safety voltage in a dangerous environment

Through the above discussion, it can be seen that the safety voltage in some special environments is much smaller than 36V, if there is a national regulation of the first-class safety voltage value, this voltage is roughly equivalent to the human body allowable current of 5mA, the human body resistance is 500, that is, it is equivalent to the human body immersed in water, and if you can not get rid of the charged body or strong spasm can lead to a fatal secondary accident

To sum up, the severity of the injury of the current through the human body is related to various factors such as the size of the current passing through the human body, the duration of the current passing through the human body, the way of the current passing through the human body, the frequency of the current and the condition of the human body Therefore, it cannot be one-sidedly believed that the voltage below 36V must be safe for the human body in any case, which should be paid attention to in real life

Below 36 volts is a safe voltage for the human body. A safety voltage is a series of voltages used to supply power from a specific power source to prevent electric shock. The level of the rated value of the safety voltage specified in our country is volts.

The safe voltage is the voltage that does not directly cause death or disability, and the "safe extra low voltage" that allows continuous contact under normal environmental conditions is 36V. The industry stipulates that the safety voltage is not higher than 36V, the continuous contact safety voltage is 24V, and the safety current is 10mA. The degree of harm to the human body of electric shock mainly depends on the size of the current passing through the human body and the length of the power on time.

The greater the current intensity, the greater the fatal danger; The minimum value of current that can be perceived by a person is called the perceived current, which is 1 mA for AC and 5 mA for DC; The maximum current that a person can get rid of after an electric shock is called getting rid of the current, which is 10mA for AC and 50mA for DC; The current that is life-threatening in a relatively short period of time is called a lethal current, such as a current of 100mA passing through the human body for 1s, which can be enough to make a person fatal, so the lethal current is 50mA. In the case of protection against electric shock, the current allowed by the human body can generally be considered as 30mA.

The safe voltage is the voltage that does not directly cause death or disability, and the "safe extra low voltage" that allows continuous contact under normal environmental conditions is 36V.

It is stipulated that the safety voltage is not higher than 36V, the continuous contact safety voltage is 24V, and the safety current of the only side fiber is 10mA. The greater the current intensity, the greater the fatal danger;

1. The nominal voltage does not exceed AC 50V and DC 120V;

2. Powered by safety isolation transformer;

3. The safety voltage circuit is isolated from the power supply circuit and the ground.

Voltage is the reason why the free charges move in a direction to form an electric current in a circuit. Its magnitude is equal to the work done by the unit positive charge to move from point A to point B due to the action of the electric field force, and the direction of the voltage is specified as the direction from the high potential to the low potential. The SI unit system of voltage is volts (V, referred to as volts), and the commonly used units are millivolts (mV), microvolts (V), kilovolts (kv), etc.