Electric shock protection is an important part of the electrical safety design of power battery systems. Generally speaking, it can be achieved through two methods: one is direct contact protection, such as insulation design, screen protection (barrier/shell, IPXXB/IPXXD, etc.); It is indirect protection, including equipotential connection and electrical isolation (electrical clearance, creepage distance). Here we talk about some understanding and understanding of equipotential.

　　What is equipotential bonding?

　　In electrical terminology, equipotential bonding is also called protective grounding. The book "Lightning and Lightning Protection Engineering" defines equipotential as follows: "Equipotential bonding is to connect all metal objects in and near the building, such as steel bars in concrete. , water pipes, gas pipes and other metal pipes, machine base metal objects and other large buried metal objects, cable metal shielding layers, the neutral line of the power system, and the building's grounding wire are all connected by electrical connections (welding Or reliable conductive connection) makes the metal objects inside the entire building a good equipotential body."

　　In the national standard GB/T18384-3: 2015 "Safety Requirements for Electric Vehicles Part 3", equipotential connection (potential equalization) is defined as: minimizing the potential difference between exposed conductive parts of electrical equipment.

　　Why is equipotential bonding required?

　　In the process of continuous development and updating of electrical safety technology, people have noticed that a large number of electrical accidents are caused by excessive potential differences. For example, lightning casualty accidents are caused by the tens of thousands of volts generated by lightning directly applied to the human body and the body. The huge potential difference between the earth and the earth produces a large instantaneous current, causing people who are struck by lightning to be injured or killed due to respiratory arrest or cardiac paralysis. Compared with lightning strike accidents, more people around the world are injured or killed due to electric shocks from civil or industrial electricity. The principle is the same as lightning strike accidents. It is due to the huge potential difference generated by charged objects in different parts of the human body, which in turn causes serious injury.

　　The international community attaches great importance to the role of equipotential bonding. It is very necessary for electrical safety, lightning protection, and the normal operation and safe use of electronic information equipment. After equipotential connection, fault voltage in the system power line can be prevented from causing electric shock accidents. At the same time, it can reduce the probability of potential difference, arc, and sparks, and avoid electrical fire accidents and personal electric shock accidents caused by ground faults.

　　The main functions of equipotential bonding are as follows:

　　To prevent personal electric shock: Make a good metal connection between the uncharged metal conductor part of the electrical equipment during normal operation and the ground electrode to protect human safety and prevent personal electric shock.

　　Ensure the normal operation of the electrical system: The grounding of the power system is generally the neutral point grounding. The grounding resistance of the neutral point is very small, so the potential difference between the neutral point and the ground is close to zero.

　　Prevent the hazards of lightning strikes and static electricity: Static electricity induction and electromagnetic induction will be generated during lightning strikes. Static electricity caused by friction during the production and transportation of materials may cause electric shock or fire hazards.

　　In electric vehicle products, if the maximum voltage of the entire battery pack exceeds 60V (DC), it has exceeded the safe voltage range of the human body, and equipotential connections must be made to ensure safe use.

　　In the case of equipotential bonding, even if the insulation between the positive or negative electrode of the battery pack and the battery pack case fails due to a fault, since all exposed metal parts on the vehicle have reached the same potential through equipotential bonding, the human body is exposed to these When using metal parts, no current will be generated, the human body is still safe on the vehicle, and no electric shock accident will occur.

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