counter-measure
If the shell is charged and has obvious tingling, this situation may belong to electric leakage, which can be detected by the method we introduced earlier. In this case, we should start with preventing leakage. In practice, the author summarizes three methods for your reference:
① The simplest method is to exchange the positions of live wire and neutral wire (for example, rotate the two-phase plug by 180 degrees before inserting it into the socket). This method is generally effective. Because some electrical appliances must follow the principle of "left zero and right fire", the phenomenon of shell leakage will occur after reverse insertion. Especially computers and printers, we should strictly follow this principle.
I have encountered this situation. After the plug is inserted backwards, the computer host and printer are charged, and their hands are afraid to touch the metal shell. When tested with an electric pen, the neon bubble is very bright. Measured with a multimeter, the voltage between it and the ground actually reached 1.6 volts. After switching the positions of the live wire and the zero wire, there is no electricity at all.
② Clean the dust on the circuit board, especially the dust on the power motherboard. Because if there is too much dust, sometimes it will conduct electricity (especially when it is wet), and the shell may be charged after the high and low voltage parts are connected. In this case, the dust on the circuit board should be cleaned up. If it is difficult to remove dust after getting wet, you can clean it with anhydrous alcohol, and then blow dry it with a hair dryer to drive away the moisture.
(3) If all the above methods fail, the most effective method is to ground the enclosure. Lead this electricity underground, and people will not be "electrified"
In fact, our computers are usually connected with multiple peripheral devices in daily applications, such as monitors, printers and scanners, and even local area networks. As long as one device leaks electricity, electricity will be connected to each device through data lines or network cables. Therefore, we sometimes feel that there is electricity in the main chassis of the computer, but it is not necessarily the leakage of the main computer. We should disconnect and check one by one to find the "leak culprit".
Leakage protection switch or leakage protection socket should be installed, which has good effect on preventing serious leakage accidents.
Extended data
selection principle
In order to regulate the correct use of leakage protectors, the state has promulgated a series of standards and regulations, such as Safety Supervision Regulations for Leakage Protector (Old (1999)No. 16) and Installation and Operation of Leakage Protector (GB 13955-92).
According to these standards and regulations, we should follow the following main principles when choosing leakage protectors:
1. When purchasing the earth leakage protector, you should buy the products of qualified manufacturers, and the product quality inspection is qualified. I would like to remind you that many leakage protectors sold in the market are unqualified products.
On June 28th, 2002, the General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) announced the results of random inspection on the quality of leakage protectors, and about 20% of the products were unqualified. The main problems are: some can't break the short-circuit current normally, eliminating the fire hazard; Some can't protect people from electric shock; Don't trip during other trips, which will affect the normal power consumption.
2. The power supply voltage, working current, leakage current, action time and other parameters of the leakage protector should be determined according to the protection scope, personal equipment safety and environmental requirements.
3. When the power supply adopts classified protection of leakage protector, the selectivity of upper and lower switches shall be satisfied. Generally, the rated leakage current of the upper level leakage protector is not less than the rated leakage current of the lower level leakage protector, which can sensitively protect personal and equipment safety, avoid over-the-top tripping and narrow the scope of accident inspection.
4. Hand-held power tools (except Class III), mobile household appliances (except Class III), other mobile electromechanical equipment and electrical equipment with high risk of electric shock must be equipped with leakage protectors.
5, the construction site temporary electrical equipment lines, leakage protector should be installed. The Technical Specification for Temporary Electricity Safety in Construction Site (JGJ46-88) has clear requirements for this.
6, organs, schools, enterprises, residential buildings, hotels, restaurants and guest rooms in the socket circuit, must also be installed leakage protector.
7. Power supply lines and equipment installed in water, as well as places with good conductivity such as high humidity, high temperature and high metal occupancy rate, such as workplaces in machining, metallurgy, textile, electronics, food processing and other industries, as well as boiler rooms, water pump rooms, canteens, bathrooms, hospitals and other places, must be protected by leakage protectors.
8. The distribution box with leakage protector should be selected for fixed line electrical equipment and normal production and workplace. Temporary use of small electrical equipment, should choose leakage protection plug (seat) or socket box with leakage protector.
9. As a supplementary protection of direct contact protection (not the only direct contact protection), the leakage protector with high sensitivity and fast action should be selected.
Generally, the operating current shall not exceed 30mA, and the operating time shall not exceed 0.1s.. These two parameters ensure that if the human body gets an electric shock, it will not cause pathological physiological danger to the electric shock.
The rated working current of leakage protectors in bathrooms, swimming pools and other places should not exceed 10mA.
When electric shock may lead to a secondary accident, a leakage protector with a rated working current of 6mA should be selected.
10. For electrical equipment that is not allowed to be cut off, such as channel lighting, emergency lighting, power supply for fire-fighting equipment, anti-theft alarm power supply, etc. Alarm-type leakage protectors should be used in public places, connected with acousto-optic alarm signals, and the management personnel should be informed to deal with the faults in time.
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