The high-voltage cable is a kind of power cable, which is used to transmit power cables of 10KV or more, and is mostly used for main roads of power transmission.
For cables below 35KV, the current carrying capacity is calculated as the normal cable; for cables of 35KV and above, the current carrying capacity should be calculated according to the economic current density. Next, Xiaobian will introduce the high-voltage cable current-carrying flow comparison table, calculation formula and influence conditions.
High-voltage cable current carrying capacity comparison table (take 10KV high-voltage cable as an example)
YJV, YJLV-8.7/10KV, 8.7/15KV cross-linked power cable
High-voltage cable current carrying capacity calculation formula
For cables of 35KV and above, theoretically, the formula for calculating the current carrying capacity of high-voltage cables: maximum current carrying capacity (J) = cable breakage area (A: mm2) × economic current density (J: A/mm2)
Cable economic current density meter
The unit of economic current density is: ampere/square millimeter
High-voltage cable current carrying capacity
The above formula is the ideal condition, the calculation of the current carrying capacity of the high-voltage cable. For the actual use, the cable system operating environment and operating parameters have a great influence on the conductor cross-section selection. The cables of the same conductor cross-section are under different environmental and operating conditions. The current carrying capacity is very different. The various factors affecting the cable current carrying capacity will be analyzed one by one below.
1, the buried depth of the cable
In order to protect the cable buried in the ground, reduce or avoid the influence of external force on it, the general cable line must ensure a certain depth. However, as the depth of burial increases, the cable cooling conditions also deteriorate. Under the same conditions that allow the high operating temperature of zui, the cable current carrying capacity also becomes smaller as the buried depth increases.
2. Mutual heating effect of multi-loop cable
When the cable multi-circuit is laid in a dense form, the heat dissipation condition between the multi-circuit cables will be deteriorated due to the mutual heat effect, so the current carrying capacity is correspondingly reduced.
3. The influence of the distance between the same return cables
Similar to the mutual heat effect between multiple return cables, there is also a mutual heat effect between the same return cables.
4. Soil temperature around the cable system
The choice of cable cross-section is to determine the allowable current of the cable, and the allowable current is determined by the allowable temperature of the core. The core temperature is not only related to the current, but also depends on the surrounding medium temperature and thermal resistance. Therefore, the soil temperature around the buried cable has a large impact on the current carrying capacity.
5. Soil thermal resistance coefficient
In the initial assessment of cable current carrying capacity, such as soil is not abnormally dry or hot.
Generally, for larger-scale cable systems, it is required to make detailed measurements when conducting line surveys before design, and confirm the soil thermal resistance coefficient along the line. In addition, the soil thermal resistance coefficient should be considered as the season changes.
6, other relevant data
If the cable is not laid directly in the pipeline but laid in the pipeline and buried in the ground, in addition to collecting the above operational and environmental data, the thermal resistance coefficient of the conduit is also required, which is also an important data affecting the current carrying capacity of the cable.
The above content is related to the high-voltage cable current-carrying flow comparison table, calculation formula and influence conditions introduced by Xiaobian. Cables play a vital role in our daily lives. It is recommended to consider the current carrying capacity of the cable (especially high voltage cables) or to check the manual and the manufacturer.
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