Technical measures to prevent electric shock

2022-09-22
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Technical measures to prevent electric shock

1. Insulation

it is the effect of preventing human body from touching the insulator and sealing the charged body due to the attached force. Porcelain, glass, mica, rubber, wood, bakelite, plastic, cloth, paper and mineral oil are all commonly used insulating materials

it should be noted that many insulating materials will lose their insulating properties after being damped or will be damaged under the action of strong electric field

2. Screen protection

refers to the use of barriers, passports, cover box gates, etc. to isolate the charged body from the outside world

generally, the movable part of the electrical switch cannot be insulated, but needs screen protection. High voltage equipment, whether insulated or not, shall be protected by shielding

3. Spacing

is to ensure the necessary safety distance. In addition to preventing touching or too close to the live line, the spacing can also prevent fire, prevent mixed lines, and facilitate operation. In low-voltage operation, the minimum maintenance distance shall not be less than 0.1M

b. grounding and neutral connection

grounding

refers to the direct connection with the earth. The artificial connection between a point of the live part of the electrical device or electrical line and the earth, and a point of the non live part of the electrical device or other devices under normal conditions is called grounding

protective grounding

in order to prevent the electrical equipment from encouraging differential development, the practice of closely connecting the electrical equipment with the grounding body deeply buried underground through the protective grounding wire is called protective grounding

protective grounding measures shall be taken for metal parts that may present dangerous voltage due to insulation damage or other reasons. For example, the metal shells of motors, transformers, switchgear, lighting fixtures and other electrical equipment should be grounded. In general low-voltage systems, the protective grounding resistance value should be less than 4 ohms

protective neutral connection

is to closely connect the uncharged metal part of electrical equipment with the electrical zero line under normal conditions. The cooling system must be turned on when the oil temperature exceeds 60 ℃; Note that in the three-phase four wire power system, the metal shell of electrical equipment is usually grounded and connected to neutral at the same time, which is the so-called repeated grounding protection measure. However, it should also be noted that fuses and switches are not allowed to be installed in the zero line circuit

c. install leakage protection device

in order to ensure the safety of personnel and equipment in case of fault, leakage current action protector should be installed as far as possible. It can obtain abnormal signals through the conversion of the detection mechanism of the protection device in case of leakage of equipment and lines, convert and transmit them through the intermediate mechanism, and then promote the action of the actuator to automatically cut off the power supply and play a protective role

d. adopt safe voltage

this is a safety measure for small electrical equipment or small capacity electrical lines. According to Ohm's law, the greater the voltage, the greater the current. Therefore, the voltage that may be applied to people can be limited to a certain range, so that under the voltage of the whole production process of Zhongfu high precision aluminum company, the company's transformation and upgrading project, which the reporter saw with his own eyes in the production workshop of Yulian group, the current passing through the human body does not exceed the allowable range. This voltage is called safe voltage. The power frequency effective value of the safety voltage shall not exceed 50 volts, and the DC voltage shall not exceed 120 volts. In China, the grades of power frequency RMS are 42 V, 36 V, 24 V, 12 V and 6 v

if there is no special safety structure or safety measures for portable lamps and general lamps with a height of less than 2.5 meters, 42 V or 36 V safety voltage should be used

12 volt safety voltage should be used when using portable lighting in the environment where the working place in metal containers, tunnels, mines and other places is narrow, inconvenient to move, and there is a large area of grounding conductor around

e. reinforced insulation

reinforced insulation is the use of double insulation or additional overall insulation, that is, to protect the insulator from electric shock after the usual insulation damage

precautions

1. Do not touch or repair the electrical equipment in the workshop without permission

2. The distribution boxes, distribution boards, knife switches, button heads, sockets, pins and wires that are often contacted and used must be kept in good condition without damage or exposing the live parts

3. Do not replace the fuse with copper wire, and keep the cover surface of knife switch, magnetic switch, etc. intact, so as to prevent electric arc or fuse flying injury in case of short circuit

4. Regularly check the protective grounding and neutral connection devices of electrical equipment to ensure that the connection is firm

5. When moving electric equipment such as electric fans, lighting lamps and welding machines, the power supply must be cut off first, and the wires must be protected to avoid wear or breakage

6. When using hand-held electric tools such as electric drills and electric grinding wheels, leakage protectors must be installed. The shell of the tool should be protected from grounding or neutral, and the wire should be prevented from being broken when moving the tool. During operation, wear insulating gloves and stand on the insulating board

7. In thunderstorms, do not walk within 20 meters around the grounding conductors of high-voltage poles, towers and lightning rods. When the high-voltage line is broken, no one is allowed to enter within 10 meters around; If it is within 10 meters, you should jump out of the danger zone with one or both feet

8. When repairing the equipment, be sure to cut off the power supply, and place a warning sign prohibiting switching on and someone working in an obvious place

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