The harm of human body static electricity

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Issue Time: May 14,2021

Summary

The harm of human body static electricity

The hazards of static electricity on the human body include the following:

1. Human body electric shock

When a charged human body approaches ground, the instantaneous impact current generated by electrostatic discharge will flow through a certain part of the human body and cause an electric shock. The degree of electric shock is related to the energy stored in the human body. The greater the energy (large body capacitance or high human body potential), the more severe the electric shock will be. Similarly, when an uncharged human body approaches a charged object, a human body shock event will occur due to electrostatic discharge. The severity of the electric shock is related to the electrostatic energy, voltage and the capacitance of the charged body. (The following table shows the physiological effects of the human body when an electrostatic body with a capacitance of 470 PF has a human body shock.)

The relationship between electrification of the human body and the degree of electric shock induction

Human body charged potential (KV)	Electric shock induction intensity
1.0	No feeling
2.0	Feeling on the outside of the finger, but not painful
2.5	There is a tingling sensation in the discharge part, a slight trembling sensation, but no pain
3.0	Acupuncture-like pain
4.0	There is a slight pain in the fingers, as if a needle is often pierced
5.0	Pain of electric shock from palm to forearm
6.0	Feel intense pain in my fingers and a heaviness in my wrist after electric shock
7.0	Strong pain and numbness in fingers and palms
8.0	Numbness from palm to wrist
9.0	Strong pain in the wrist, numb and heavy hand
10.0	Pain in the whole hand and sensation of current flow
11.0	The fingers feel violent numbness, and the whole hand has strong tactile induction
12.0	Under strong electric shock, all hands feel like being beaten severely

2. Cause an explosion and fire

The human body capacitance is generally 100PF. Assuming that the human body potential is 2kv, the electrostatic energy stored by the human body W=1/2 CUx100x10-12x22x (103)2= 0.2(M]). Since the human body resistance is generally about 1.5KQ2, the human body charging (discharging) time constant RC= 100x10-12x1.5x10*= 0.15x10*6(S), that is, the energy stored by the human body can be discharged at 0.15 by electrostatic discharge Discharge in a very short time of microseconds. This level of energy is sufficient to initiate the combustion and explosion of part of the gas mixture. -Generally speaking, the minimum ignition energy value of dust is higher, so the possibility of dust combustion and explosion caused by electrostatic discharge of the human body is very small, but for titanium powder, zirconium powder and other layered powder clouds with extremely low minimum ignition energy, the same threatening.

3. The human body causes obstacles to the work of electrostatic sensitive electronic products

The human body's electrostatic barrier is manifested in two aspects. On the one hand, because the discharge time of the electrostatic energy of the human body is very short, only a few tenths of a microsecond, the instantaneous pulse is high, and the average power is more than kilowatts, which can burn sensitive components and cause the entire electronic equipment or system to malfunction and malfunction. . On the other hand, since the electrostatic potential of the human body can be as high as hundreds, thousands or even tens of thousands of volts, it is enough to cause electrical breakdown of sensitive electronic components, including hard breakdown (causing sudden and permanent failure) and soft breakdown (general performance). Is temporarily invalid). Temporary failure will not only cause errors and errors in the work of the equipment, but the more serious hazard is that it can cause potential failures with no rules to follow, and reduce the reliability of electronic products.