The actual parallel use of cables in the process of single-core cables in parallel more, single-core cables in the actual parallel use of the process may be due to the impact of the laying method, the actual flow capacity is not necessarily able to meet the needs of the actual load, the actual use of the phenomenon of overloading may occur. In fact, when the 6 cables without gap parallel yard in the air after laying its actual re-flow can only reach the theoretical flow of about 60%, if coupled with the cable load according to the theoretical selection, not in accordance with the actual laying situation for correction. It is likely to cause the cable in the actual energization process on the full load running state, resulting in the cable energized to run the heating phenomenon. Therefore, in the parallel laying of cables in the process of its actual flow-carrying is not simply the existence of "1 +1 = 2" relationship, there may well be "1 +1 = 1.5" or even "1 +1 = 1" phenomenon, resulting in the actual operation of the cable in the process of serious heating phenomenon. Now we give a simple example, such as the capacity of 570KW, rated current of 1140A or so of the three-phase asynchronous motor load, using two YJV-0.6/1KV-1 * 300 cable in parallel for power supply, according to the theoretical design calculations for the given value, YJV-0.6/1KV-1 * 300 a single cable in the air from the theoretical calculations of the load capacity of about 750A The theoretical parallel flow of two cables can reach about 1500A, which can fully meet the actual use of the equipment. We now assume that there are 32 cables all concentrated in a side-by-side stacked random yard laying on the bridge, and the above parallel power supply of the two YJV-0.6/1KV-1 * 300 is also located in which. Check the relevant materials found that when the cable in the air 6 gapless stacked yard after the cable's actual current-carrying capacity will fall to the theoretical calculation of the given value of 60%. Then the original cable of the actual load capacity of 1500 × 60% = 900A, each cable assigned to the actual load capacity of 450A or so, and the theoretical calculation of the load capacity of 750A difference of nearly 300A, so that the cable in the actual use of the process of the existence of a serious overload heating phenomenon. 　　

And the actual laying of the number of cables is much more than 6, then the actual cable flow may be smaller than 900A. How to solve this problem, some people propose to parallel a YJV-0.6/1KV-1 * 120 cable to reduce the remaining two cables to the distribution of the current, and now we are theoretically assumed to calculate the first three cables in parallel, the actual distribution of load current, assuming that the length of three cables in parallel are 1 kilometer, the laying temperature of all according to the calculation of 20 ℃. And assume that the parallel 1 kilometer two YJV-0.6/1KV-1 * 300 cable conductor resistance is identical. In fact, due to manufacturing process problems can not be completely consistent, conductor resistance or a small difference. In the actual calculation process, we ignore the above impact. 20 ℃ copper conductor maximum DC resistance copper core 300 mm2 for 0.0601Ω/km, 120 mm2 for 0.153Ω/km, 1140A of the current of the actual distribution of the calculation of the 120 mm2 cross-section distribution of the current is (0.0601 * 0.0601/0.153 * 0.0601+0.153 * 0.0601 + 0.0601 + 0.0601 + 0.0601 + 0.0601 + 0.0601 + 0.0601 + 0.153 * 0.0601 + 0.153). 0.0601 + 0.0601 * 0.0601) = 187A, the remaining 300 mm2 cross-section of the current allocated to 953A, and each 300 mm2 cable on the actual flow of the load current of 477A or so, so that the actual energization of the cable is still overloaded. The cable 120 of the actual disaster flow in this case, the load current of 435 * 60% = 261A, there is still a large margin but the law of current distribution will not be allocated to the 120 cross-section of the cable up, in fact, the original problem is still not solved. Moreover, our assumption that there are only 6 cables does not meet our established requirements. Imagine then add a 300 mm2 cross-section of the cable, the actual distribution of current-carrying capacity of the law of 1140 * 1 / 3 = 380A, so in the actual process of parallel cable to the home of the cable cross-section must be calculated after the strict corrections to be used in parallel, otherwise in time to add the cable may not be able to solve the problem, the best case is to use the same specifications to add the same size of the cable and to ensure that the length is the same, so as to ensure the basic uniformity of cable distribution, and to ensure the same length. This ensures that the distribution of current is basically uniform. In fact, after the completion of all the field installation and then another on-site cable reinstallation and rework, in general, is very difficult to achieve. Therefore, the cable prior to the formal design and laying of the installation work is critical, the way taken later is often just a