In the explosion-proof electrical equipment, the explosion-proof clearance and creepage distance are an extremely important index to ensure the explosion-proof electrical performance and safety performance of the explosion-proof electrical equipment. The so-called explosion-proof clearance refers to the shortest distance in the air between live conductors of different potentials, which is related to the effective value of the working voltage; The so-called creepage distance refers to the shortest path between live conductors of different potentials on the surface of the insulating material, which is not only related to the effective value of the working voltage, but also related to the degree of surface contamination of the insulating material's tracking resistance index level. Explosion-proof clearances and creepage distances for different voltage classes and different material grades. Refer to the corresponding specified values in the relevant table.
Fig.1 GB 3836.3—2010/IEC 60079-7:2006 explosion-proof clearance and creepage distance
In the design of explosion-proof electrical equipment with increased safety, when necessary, designers can set or increase explosion-proof clearance and creepage distances on the insulating parts. Effective ribs and grooves on the insulating components should conform to:
1. The height of the rib should be at least 2.5mm, and the thickness should be suitable for the mechanical strength of the material, at least 1mm.
2. The depth and width of the groove should not be less than 2.5mm.
When more than two insulating parts are bonded together with a compliant binder, such a binder is considered a type of part.
For the convenience of design and calculation, the following are examples of explosion-proof clearance and creepage distances of various shapes of insulating parts for people's reference. The schematic diagram for calculating the explosion-proof clearance and creepage distance is shown in Figure 2-Figure 12.
In addition to the diagram shown, one can use other equivalent structures, but the basic principles mentioned above should be followed when adopting other structures.
Figure 2: One example of explosion-proof clearance and creepage distance
Note: If there is a groove with a width of less than 2.5m on the insulation surface between the two live conductors (the depth is not counted), the explosion-proof clearance and creepage distance are the shortest distance between the two live conductors and the shortest path of the insulating surface.
Figure 3: Example 2 of explosion-proof clearance and creepage distance
Note: If there is a groove with a width greater than 2.5mm on the insulation surface between the two live conductors (the depth is not counted), the explosion-proof electrical clearance is the shortest distance between the two live conductors, and the creepage distance is the shortest path along the surface of the insulator (including the concave).
Figure 4: Example 3 of explosion-proof clearance and creepage distance
Note: If there is a V-shaped groove with a width greater than 2.5mm on the insulating surface between two live conductors, the explosion-proof electrical clearance is the shortest distance in the space between the two live conductors, and the creepage distance is the shortest path along the surface of the insulator (including the groove, but the bottom of the groove is calculated at 2.5mm).
Fig.5 Example 4 of explosion-proof clearance and creepage distance
Note: If there is an inverted V-shaped rib on the insulating surface between two live conductors, the explosion-proof electrical clearance is the shortest distance between the two live conductors across the top of the rib, and the creepage distance is the shortest path along the surface contour line of the insulator (including the inverted V-shaped rib).
Figure 6: Explosion-proof clearance and creepage distance example 5
Note: If there are unbonded insulating joints on the insulating surface between two live conductors, and there are grooves with a width of less than 2.5mm on both sides, the explosion-proof clearance and creepage distance shall be the shortest distance between the two live conductors (through the unbonded gap).
Figure 7: Example 6 of explosion-proof clearance and creepage distance
Note: If there is a bundle of bonded insulating joints on the insulating surface between two live conductors. There are dents with a width greater than 2.5 mm on both sides, and the explosion-proof electrical clearance is the shortest distance in the space between two live conductors (through the unbonded gap). The creepage distance is the shortest path between two live conductors (through unbonded gaps) along the insulating surface concave wheel line.
Figure 8: Example 7 of explosion-proof clearance and creepage distance
Note: If there is an unbonded insulating joint on the insulating surface between two live conductors, there is a depression with a width greater than 2.5mm on one side and a depression with a width of less than 2.5mm on the other side, the explosion-proof electrical clearance is the shortest distance between the two live conductors (through the unbonded gap), and the creepage distance is the shortest path between the two live conductors (through the unbonded gap) along the contour line of the groove on the insulating surface with a width greater than 2.5mm (excluding the groove with a width of less than 2.5mm).
Figure 9: Example 8 of explosion-proof clearance and creepage distance
Note: If there is an unbonded insulating joint inserted into the insulating surface between two live conductors, the explosion-proof clearance is the shortest distance between the two live conductors across the polyline space of the top of the insulating joint, and the creepage distance is the shortest path between the two live conductors along the surface of the insulating joint.
Figure 10: Explosion-proof clearance and creepage distance example nine
Note: If the spacing between the screw head and the dimple wall is greater than 2.5mm, this distance should be included in the calculation of the creepage distance, but attention should be paid to the hexagonal head position of the hexagonal head screw.
Fig.11 Example 10 of explosion-proof clearance and creepage distance
Note: If the spacing between the screw head and the concave wall is less than 2.5mm, this distance should not be included in the calculation of the creepage distance, but the hexagonal head position of the hexagon head screw should be noted.
Figure 12: Example 11 of explosion-proof clearance and creepage distance
Note: If there is an ungrounded inactive conductor (2) on the insulating surface between the two live conductors (1), the explosion-proof clearance and creepage distance are the sum of the distances between the uncharged conductors and the two live conductors (i.e., d+D). If the uncharged conductor (2) is grounded. Then the explosion-proof clearance and creepage distance of the live conductor (1) to the uncharged conductor (2) shall be calculated according to the normal situation.