Equipotential bonding of the hottest buildings can

  • Detail

The equipotential bonding of buildings cannot be ignored

Abstract: This paper discusses the relevant problems of equipotential bonding of buildings in China at present

key words: equipotential bonding grounding bonding terminal board electric shock Untitled Document the international community attaches great importance to the role of equipotential bonding, which is very necessary for power safety, lightning protection and the normal work and safe use of electronic information equipment. According to theoretical analysis, the smaller the action range of equipotential bonding is, the safer it is electrically

1 grounding is a wide range of equipotential bonding

safety grounding is also an equipotential bonding, which is a wide range of equipotential bonding with the earth potential as the reference potential. In the general concept, grounding refers to grounding, and not grounding violates the basic requirements of electrical safety. This concept has limitations. Electric shock accidents and electrical fires rarely occur during the flight of the aircraft, but the aircraft is not grounded. The safety of electricity use in aircraft does not depend on grounding, but on equipotential bonding, which takes the fuselage potential as the reference potential in the aircraft. Because the range of the aircraft is very narrow, even in the case of an accident where the measured value may not be exactly the same, the potential difference is also very small, so the electrical safety on the aircraft is effectively guaranteed. People live on the earth, so they often need to be equipotential with the earth, that is, the electrical system and electrical equipment shell are connected with the earth, which is often referred to as "grounding". The aircraft can be connected with the fuselage with terminal blocks, while the earth needs to be connected with the grounding electrode as the terminal blocks

2 equipotential bonding installation of buildings

the national building standard design atlas "equipotential bonding installation" (97sd567) introduces the specific methods of equipotential bonding of buildings in detail. The scope of application of this atlas is: general installation drawings for equipotential bonding of electrical devices in general industrial and civil buildings to prevent indirect contact electric shock and explosion and fire caused by grounding fault. Lightning protection of buildings and protection of electronic information equipment from transient overvoltage and interference and other equipotential bonding installations should also be constructed in accordance with their corresponding requirements

2.1 classification of equipotential bonding and its conductive part

(1) total equipotential bonding (MEB)

the function of total equipotential bonding is to reduce the indirect contact voltage in the building and the potential difference between different metal parts, and eliminate the harm of dangerous fault voltage introduced from outside the building through electrical lines and various metal pipelines, It shall connect the following conductive parts with each other through the main equipotential bonding terminal board (grounding busbar) near the incoming distribution box; PE (pen) busbar of incoming distribution box; Metal pipes of public facilities, such as pipes for water, heat, gas, etc; If possible, it should include the metal structure of the building; If manual grounding is done, it also includes its grounding electrode lead. Each incoming power line of the building shall be subject to general equipotential bonding, and each general equipotential bonding terminal board shall be connected with each other

(2) auxiliary equipotential bonding (SEB)

connect the two conductive parts directly with wires to make the fault contact voltage fall below the contact voltage limit, which is called auxiliary equipotential bonding

auxiliary equipotential bonding is required in the following cases: when the power network impedance is too large, so that the automatic power cut-off time is too long, and the requirements for preventing electric shock cannot be met; Fixed and mobile electrical equipment are supplied from the same distribution box of TN system, and the power cut-off time of fixed equipment protection appliances cannot meet the anti electric shock requirements of mobile equipment; In order to meet the special requirements of bathrooms, swimming pools, hospital operating rooms and other places for the prevention of electric shock

(3) local equipotential bonding (LEB)

when multiple auxiliary equipotential bonding needs to be made in a local area, the following parts can be connected to each other through the local equipotential bonding isocyanate (TDI) terminal board, so as to easily realize multiple auxiliary equipotential bonding in this local area, which is called local equipotential bonding: PE bus or PE trunk; Metal pipes of public facilities; If possible, including the metal structure of the building

2.2 selection of equipotential bonding wire and equipotential bonding terminal board

copper material should be used for equipotential bonding wire and equipotential bonding terminal board

(1) see Table 1 for the cross section of equipotential bonding wire

(2) the cross section of the equipotential bonding terminal board shall not be less than that of the connected equipotential bonding wire

2.3 equipotential bonding should be made in residential buildings

according to the statistics of electrical accidents at home and abroad, the short circuit of low-voltage system is mostly the grounding fault (grounding short circuit) of the phase line touching the equipment shell, metal pipeline structure and the earth, and these equipment shells, pipelines and structures have ground fault voltage, which is easy to cause personal electric shock or electrical fire accidents. Making general equipotential bonding in residential buildings can eliminate or reduce this fault voltage, Its effect is better than simple grounding. Therefore, the international electrical standard iec60364 - low-cost, fake aluminum alloy cable 4-41, the electrical standards of developed countries and China's electrical standards all stipulate it as the basic requirements of electrical safety

the bathroom is listed as a special place with high risk of electric shock by International Electrotechnical standards. Electric shock accidents also occur frequently in bathrooms in China. This is because people are soaked all over when bathing, and the human impedance is greatly reduced. The 10 ~ 20V voltage introduced into the bathroom along the metal pipe is enough to cause ventricular fibrillation and death. Therefore, an equipotential connection should be made in the bathroom according to the above requirements. Due to the equipotential effect in such a small range, the potential difference at the time of failure is negligible, which effectively ensures that the regional difference in the total amount of energy distribution in China is not only obvious, but also personal safety

in order to ensure the reliable conduction of equipotential bonding, the equipotential bonding wire and grounding busbar should adopt copper wire and copper plate respectively. Equipotential bonding, an electrical safety measure, does not require complex and expensive electrical equipment. It consumes only some conductors, which is not like the artificial grounding buried underground, which is very easy to fail due to soil corrosion (in fact, the implementation of equipotential bonding also realizes grounding, because the water pipes and foundation reinforcement connected to it have played the role of low resistance and long life grounding), Its role in ensuring electrical safety is far better than the artificial grounding that we used to use in the past. In developed countries, households are not required to enter the artificial grounding, but if the general equipotential bonding and local equipotential bonding in the bathroom are not done in the residential building, not only party a will not accept it, but the local power supply company will also refuse to supply power on the grounds of electrical insecurity

3 main problems in the implementation of equipotential bonding

3.1 uncoordinated norms and quotas

construction practice of equipotential bonding in developed countries

Copyright © 2011 JIN SHI