Insulation Design of High Voltage System of New Energy Vehicles

Traditional fuel vehicles use 12V to supply power to the interior of the vehicle (lights, wipers, windows, air conditioners, etc.), which is not prone to electric shock accidents. Electric vehicles use power batteries to drive motors, and the output voltage of high-voltage batteries (power batteries) for electric vehicles has exceeded If the system insulation is damaged, an electric shock accident will occur. The main reasons for electric shock accidents are as follows:
(1) Lack of electrical safety knowledge;
(2) Violation of operating procedures;
(3) The equipment is unqualified;
(4) Equipment in disrepair, etc.
1 Insulation related concepts
(1) Breakdown
When a destructive discharge occurs in a solid dielectric, it is called breakdown. During breakdown, traces are left in the solid dielectric, which permanently loses its insulating properties.
(2) Atomic structure
Atoms are made up of a nucleus and extranuclear electrons that orbit the center of the nucleus, much like the planets of the solar system orbit the sun. Inside the nucleus are protons, neutrons, and other elementary particles.
(3) Current
The free electrons or ions in the conductor flow regularly under the action of the electric field force. The direction in which the positive charge moves is specified as the positive direction. It is represented by the letter i and the unit is A (Ampere).
(4) Voltage
The potential difference between two points in a circuit. It is represented by the letter U and the unit is V (volts). nominal voltage The nominal voltage value of an electrical system. The properties of the system are all related to this value. Working voltage is the highest value of AC voltage (root mean square value rms) or DC voltage (regardless of instantaneous voltage) that may be generated by an electrical system under any normal operating state.
(5) Resistance
The conductor can conduct electricity and at the same time have a resistance to the current. This ability to block the flow of current becomes resistance, which is represented by the letter R, and the unit is Ω (ohm).
Inside the insulator: The electrons around the nucleus are tightly bound by the nucleus, called bound electrons, so the insulator does not conduct electricity;
Inside the conductor: There are a large number of electrons that are freed from the nucleus, called free electrons, so the conductor conducts electricity.
(6) electrical circuit
A collection of connected live parts through which current can flow.
(7)Clearance
The shortest distance in space between two conductive parts, or between a conductive part and the accessible surface of the appliance.
(8) Creepage distance
The shortest path, measured along the surface of insulating material, between two conductive parts, or between a conductive part and an accessible surface of the appliance.
(9) Direct contact
Personnel contact with live parts.
(10) Indirect contact
Contact between persons and exposed conductive parts that become live in the event of a basic insulation fault. In other words, it refers to the electric shock that the exposed conductive part of the electrical equipment has fault voltage due to insulation damage. For example, due to broken insulation, the electric shock suffered by people when moving the core of the phase line to touch the metal pillar. The shell of an electric vehicle is originally not charged. When the insulation damage of the components in the high-voltage system inside the electric vehicle causes the chassis to be charged at at least two points, if a person accidentally touches the car shell, it will cause indirect contact electric shock.