建筑物内桥架可以独立假设，可以附设在各种建(构)筑物和管廊支架上，应体现结构简单，造型美观、配置灵活和维修方便等特点，那么您知道电缆桥架的胀缩问题以及接地规定是怎样的吗？
The cable tray in the building can be assumed independently and can be attached to various buildings (structures) and pipe gallery supports, which should reflect the characteristics of simple structure, beautiful appearance, flexible configuration and convenient maintenance. Do you know the expansion and contraction problems of cable tray and the grounding regulations?
电缆桥架的胀缩问题
Expansion and contraction of cable tray
由于环境温度变化，钢质电缆桥架会出现热胀冷缩的现象。室外桥架受温度影响较大例如环境高温度为40℃，低温度为-20℃，则电缆桥架的大收缩量按下式求得：
Due to the change of ambient temperature, the steel cable tray will expand with heat and contract with cold. The outdoor cable tray is greatly affected by temperature. For example, the high temperature of the environment is 40 ℃, and the low temperature is -20 ℃, then the large shrinkage of the cable tray is calculated according to the following formula:
Δt=11.2×10-6×60deg(度)×1000mm
Δ t=11.2 × 10-6 × 60Deg (degree) × 1000mm
由此得出结论：
It is concluded that:
温差为60℃时，Δι=0.672mm/m
When the temperature difference is 60 ℃, Δι= 0.672mm/m
温差为50℃时，Δι=0.560mm/m
When the temperature difference is 50 ℃, Δι= 0.560mm/m
温差为40℃时，Δι=0.448mm/m
When the temperature difference is 40 ℃, Δι= 0.448mm/m
工程设计中直线段电缆桥架应考虑伸缩接头，伸缩接头的间距建议按以下取定：
Expansion joints shall be considered for cable trays in straight sections in engineering design, and the spacing of expansion joints is recommended to be determined as follows:
当温差为40℃时为50m;
50m when the temperature difference is 40 ℃;
当温差为50℃时为40m;
40m when the temperature difference is 50 ℃;
当温差为60℃时为40m;
40m when the temperature difference is 60 ℃;
Shandong cable tray grounding regulations
根据规范的有关规定，镀锌电缆桥架进行良好的接地。
According to the relevant provisions of the specification, the galvanized cable tray shall be well grounded.
(1)镀锌电缆桥架直接板每个固定螺栓接触电阻。(电工天下www.dgjs123.com)
(1) Contact resistance of each fixed bolt of galvanized cable tray direct plate. (electrician world www.dgjs123.com)
应小于0.005Ω，此时电缆桥架可作为接地干线(喷粉电缆桥架不宜作接地干线)，每个电缆桥架的电阻值可按下式计算：
It should be less than 0.005 Ω. At this time, the cable tray can be used as the grounding main line (the powder sprayed cable tray should not be used as the grounding main line). The resistance value of each cable tray can be calculated according to the following formula:
r=ρ·L/S
r= ρ· L/S
式中：ρ=15×10Ω-6/cm(20℃)；
Where: ρ= fifteen × 10Ω-6/cm(20℃)；
L=长度按100mm计算；
L= length is calculated as 100mm;
S=截面积cm2。
S= sectional area cm2.
(2)梯架于托盘的单位电阻值见表2。
(2) See Table 2 for the unit resistance value of ladder and tray.
表2梯架于托盘的单位电阻值
Table 2 unit resistance value of ladder to tray
(3)电缆槽的单位电阻值见表3
(3) See Table 3 for the unit resistance value of cable tray
(4)当电缆桥架安装连接程整体后，每根梯边(或每个电缆槽)的电阻为：R＝L(r＋1/3r’)
(4) When the cable tray is installed with the whole connection process, the resistance of each ladder side (or each cable tray) is: r = l (R + 1/3r ')
式中：
Where:
R--梯边，即（电缆槽）全长总电阻（mΩ）；r--梯边单位长度电阻（mΩ/m）；r’--直接板固定螺栓接触电阻。
R -- ladder side, that is, the total resistance (m Ω) of the whole length of (cable trough); R -- resistance per unit length of ladder edge (m Ω /m); R '-- contact resistance of fixed bolt of direct plate.
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