Busway Differential Current-carrying Capacity

Busbar trunk belonging to electricity transmission, it is very important engineering equipment. Currently there are many projects installed busbar current carrying capacity and the actual design of the rated current gap is large, some even less than 50% of the current carrying capacity. Because of the current construction and acceptance of GB50303-2002, busbar current carrying capacity has not been identified, together with busbar very special, the same cross-sectional area of ​​the conductor, the same copper content, busbar current carrying capacity differ greatly, so engineering quality supervision staff Busway current carrying capacity is very difficult to identify, our multi-disciplinary information and practical experience, to talk about how to effectively identify busbar current carrying capacity.

Differential busbar current carrying capacity is divided into two stages: a stage is to identify the current carrying capacity of busbar products, the second stage is to identify the conductor material and its current carrying capacity.

Wires and cables through the national laboratory tests, according to the manufacturers standard type of product production, design units come in various model specifications current form, is written on the drawing model specifications, not current. Users procurement, construction supervision, quality inspection station, just control the cross sectional area of ​​the conductor and the conductor resistivity, you can control the quality of products. But Busway different because busbar current carrying capacity is not only a cross-sectional area and the conductor resistivity, it also involves the heat capacity of product structure, skin effect, eddy current, processing, heat-resistant grade insulating materials, the surface of the conductor processing, such as conductivity conductor, so in busbar industry, the same current conductors of the manufacturers specifications are different. To identify the manufacturers Busway accurate current-carrying capacity, only to see the third-party manufacturers in the various current temperature rise test report on the exterior photos, conductor size, test current through each detection point temperature rise, etc. . If no temperature rise of the current report, only 3C type test report, the 3C certification only on the short-time withstand current split units, with a covering current range, for example, 2000A ~ 1000A/Icw = 50kA certification test only 2000A current, covered by the current is not doing the experiment, do not need to send samples, but the manufacturers describe their own reports, such reports need to cover the current conductor accounting, per square millimeter current carrying capacity is the same as the test of 2000A or difference small, or need to sample the local temperature rise test test done.


Figure1 Temperature rise test

Report only proves that the temperature rise of the conductor material test sample structure, and then the current through the sample and the temperature rise in mass production, is it possible to achieve such currents and temperature rise in the structure and production process is not Variable case, the main current carrying conductor material is a relationship, and the conductor wire and cable specifications and the same test, inspection and the resistivity of the conductor meets the specifications GB5585-2005 standard, a conductor and conductive resistivity tolerance values , conductivity.

Measured using loop resistance tester bus conductor resistivity, clip busbar ends exposed copper resistivity measurements to calculate the length, width, thickness, we can calculate the resistivity, the engineering test can identify copper clad aluminum, Head across the middle of welding of copper aluminum row, two big middle small and conductor materials and so on. GB5585-2005 standard, copper conductivity ≥ 90%, resistivity ≤ 0.01777Ω·mm2/m, aluminum row conductivity ≥ 59%, resistivity ≤ 0.029Ω·mm2/m.

① Test data

② Busway data

The formula
Resistivity: unit cross-sectional area per unit length resistance of the metal conductor is called volume resistivity, also known resistivity, ρ represents the symbol.
ρ = RS / L units of ohm · mm / m (Ω · mm 2 / m);
The formula: R-metallic conductor resistance in ohms (Ω);
S-conductor cross-sectional area, in units of square millimeters (mm 2 );
L-length of the conductor in meters (m);

Busway current carrying capacity, directly related to the Busway life, power consumption, and engineering of fire accidents, the safety of life and property is directly related to the project will have on the busbar current carrying capacity in the identification is very important.