Distance requirements for various components in the electrical cabinet
The distance setting between various components is crucial in the design and installation process of the electrical cabinet. A reasonable distance can not only ensure the safe operation of electrical equipment, avoid accidents caused by electrical breakdown, short circuit and other faults, but also ensure the normal heat dissipation of components and the convenience of maintenance operations. Different types of devices and voltage levels also have different requirements for distance. The following will provide a detailed introduction based on relevant standards and specifications.
Electrical clearance and creepage distance
(1) Electrical clearance
Electrical clearance refers to the shortest straight-line distance between two conductive components in air, mainly used to prevent short circuits caused by air breakdown due to overvoltage and other factors under normal operating conditions. According to the national standard GB/T 14048.1-2012 "Low voltage switchgear and control equipment - Part 1: General principles", for low-voltage cabinets (AC voltage not exceeding 1000V, DC voltage not exceeding 1500V), in an environment with a pollution level of 2 (generally only non-conductive pollution, occasionally causing temporary conductive pollution due to condensation):
The minimum requirement for electrical clearance is 0.5mm when the rated insulation voltage is below 60V;
The rated insulation voltage is between 60-300V, and the minimum electrical clearance requirement is 3.0mm;
The rated insulation voltage is between 300-690V, and the minimum electrical clearance requirement is 5.0mm;
The rated insulation voltage is between 690-1000V, and the minimum electrical clearance requirement is 8.0mm.
If the pollution level of the environment where the electrical cabinet is located is higher (such as pollution level 3, conductive pollution, or dry non-conductive pollution turning into conductive pollution due to expected condensation), the requirements for electrical clearance will also increase accordingly.
(2) Creepage distance
Creepage distance refers to the shortest distance between two conductive components along the surface of the insulation material, mainly used to prevent leakage, flashover, and other phenomena caused by dirt, moisture, and other factors on the insulation surface. Taking the low-voltage electrical cabinet as an example, under the condition of pollution level 2 and material group IIIa (insulation material with a relative leakage trace index CTI between 175-250):
The minimum requirement for creepage distance is 0.6mm when the rated insulation voltage is below 60V;
The rated insulation voltage is between 60-300V, and the minimum requirement for creepage distance is 3.2mm;
The rated insulation voltage is between 300-690V, and the minimum requirement for creepage distance is 5.6mm;
The rated insulation voltage is between 690-1000V, and the minimum requirement for creepage distance is 8.0mm.
When the pollution level, material group, and other conditions change, the value of creepage distance also needs to be adjusted according to the standard.
