Precautions for parallel use of power cables
First, the two power cables used in parallel should have the same model, specifications and length. This way, when the cables are energized, the parameters of the two power cables are basically similar, the current carrying capacity is basically evenly distributed, and there will be no problem of a single cable being overloaded and prematurely causing large-area overheating and burning.
Secondly, the distance between parallel-operated cables should be appropriately increased so that when one cable fails, it will not affect the adjacent parallel-operated cables and burn out simultaneously, which reduces the company's economic losses in electricity to a certain extent.
Third, for power cables operating in parallel, the contact status between the cable lugs and the switch contacts at both ends must be frequently checked to ensure a good connection between the cable and the switch. This is because most cables used in parallel are larger than 35mm² , with conductor resistance per kilometer below zero ohms and on the order of 10⁻¹ . If the cable lugs do not make good contact with the switch, it can easily lead to excessive contact resistance in one or more phases of one cable at the switch, resulting in uneven current carrying capacity distribution between the two cables. Nowadays, considering economic factors and power grid design, cable customers do not leave a large margin in the selection of cable models and specifications. When the contact resistance at the lugs is too high, it can either cause the lugs to overheat and burn out due to continuous use, or it can cause a shift in the current carrying capacity of the two cables, leading to overheating and burning out of one of the cables.
Fourth, another point worth mentioning is that when multi-core armored power cables are used in parallel in an AC power grid, each cable's A , B , and C phases must be isolated and connected separately to the A , B , and C phases of the switch. It is strictly forbidden to short-circuit all the cores of a cable and then connect it to one phase of the switch. This is because doing so would be equivalent to the cable operating on a single phase, and the single-phase alternating current would generate eddy currents in the steel strip, leading to a thermal burn-out accident.
