1. The power cable should always operate within its rated current capacity to ensure long-term safe use. If the core wire is exposed to excessive heat for a prolonged period, it can cause the entire cable to overheat, leading to potential failure at the terminal or intermediate joints. This overheating may result in insulation degradation due to moisture ingress and eventually thermal breakdown. Therefore, it's crucial to monitor both the load current and the surface temperature of the cable. For cables used in parallel, special attention must be given to prevent uneven load distribution, which could lead to overheating at one end.
2. It is not recommended to use a recloser device on cable distribution lines. In the event of a permanent fault, such as an internal short circuit in the terminal or middle joint, the recloser might trigger a trip, potentially expanding the fault and disrupting system stability. Therefore, to avoid unnecessary risks, the use of a reclosing device on cable distribution circuits is strongly discouraged.
3. After a circuit breaker trips on a cable line, a thorough inspection of the cable should never be ignored. First, check if there are any faults in the connected equipment, such as short circuits or other issues. Additionally, visually inspect the cable for any physical damage—like water intrusion at outdoor terminals, overheating that may have caused insulation failure, or signs of excavation that might have damaged the cable. If necessary, further testing should be conducted to ensure safety before restoring power.
4. Special care must be taken with directly buried cables: - Avoid excavating near the cable route without proper planning. - Do not place heavy objects, corrosive materials, or temporary structures on the ground above the cable path. - Never move or remove cable markers or protective covers. - Ensure that cables entering buildings are properly sealed to prevent water leakage.
5. If a cable has been out of service for some time, it should not be put back into operation without proper testing. Over time, cables may absorb moisture, which can compromise their insulation properties. If the downtime exceeds one week but is less than a month, it’s advisable to perform an insulation resistance test before reactivation. The results should not drop by more than 30% compared to previous records. If they do, a DC withstand voltage test at half the standard preventive test voltage should be carried out. If the cable has been out of service beyond the scheduled testing period, a full preventive test according to industry standards is required.
By following these guidelines, you can significantly reduce the risk of cable failures and ensure the reliability and safety of your electrical systems.
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