When multiple cables are running in parallel, load measurement shall be conducted regularly to understand the load distribution and correctly grasp the operation status of ACSR Cables.
The load distribution of multiple cables is uneven when running in parallel, and even one phase load of one cable will be close to zero. The main reason for the serious uneven load distribution is the large difference of contact resistance of terminal connection (especially outdoor copper aluminum transition contact).
Because, the corrosion battery with two different metal contacts will cause poor contact; Due to the change of load current, temperature and natural environment, contact resistance of contact will increase to different extent. In this way, the current distribution is not uniform. For example, three cables a, B and C are running in parallel. If the contact resistance of cable a contact is large, the current is small and the normal load is mostly transferred to ABC Cables B and C. This may cause overload of cable B and C. if the contact of cable B terminal is heated due to the increase of load, the contact will be burnt and the load will be transferred to cable C, resulting in overload, thus forming a vicious cycle, and even heating will be caused by serious uneven distribution of three-phase current on the cable armour. This phenomenon will certainly endanger the safe operation of cable lines, and should be paid full attention.
Note: in design, the cable model and path length used in parallel are the same in general. Even if the models are different, the current distribution problem will be considered to meet the actual operation requirements. The provisions of this article are designed to consider that different types of cables are used for laying parallel cables due to tight construction period and incomplete cable goods, which may cause overload of one cable and insufficient load of another cable to affect operation safety. Because of the different insulation types of cables, the maximum allowable operating temperature of the core is different, and the allowable carrying capacity of the cables with the same material and specification and different insulation types is also different. Therefore, if different types of cables are used in construction, the length of cables shall be the same as possible during laying, so as to avoid the impact of operation safety due to the disproportionate distribution of load.
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