Matters needing attention in the operation of power cable in power distribution room - Database & Sql Blog Articles

SMD Aluminum Electrolytic Capacitor

Photocoupler

1. The power cable should always operate within its specified current-carrying capacity to avoid long-term overheating. Prolonged heating of the core wire can cause the entire cable to heat up, potentially leading to failure at the terminal heads or intermediate joints. This 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 should be given to ensure even load distribution to prevent overheating at one end.

2. It is not advisable to use a reclosing device on cable distribution lines. This is because a fault such as an internal short circuit at the terminal head or middle joint is typically permanent. If the recloser activates after a trip, it could worsen the situation and jeopardize the stability of the entire system. Hence, reclosing devices should generally be avoided for cable-based distribution systems.

3. After a circuit breaker trips on a cable line, a thorough inspection should never be overlooked. First, check if there are any faults in the equipment connected to the line, such as short circuits. Also, inspect the cable’s physical condition—look for signs of water ingress at outdoor terminals, overheating at indoor joints that might have caused insulation failure, or damage from nearby excavation work. If necessary, further testing should be conducted to confirm the cable’s integrity before re-energizing.

4. Special care must be taken with directly buried cables: - Do not excavate near the cable route without proper planning. - Avoid stacking heavy objects, corrosive materials, or temporary structures on the ground above the cable path. - Never move or remove protective structures along the cable route. - Ensure that cables entering buildings remain watertight to prevent water leakage.

5. Cables that have been out of service for a period should not be reactivated without proper testing. Over time, cables can absorb moisture, which may compromise their insulation. If the cable has been disconnected for more than a week but less than a month, a megohmmeter test should be performed before reactivation. The insulation resistance should not drop by more than 30% compared to previous readings. If it does, a DC withstand voltage test at half the standard preventive test voltage should be carried out. If the downtime exceeds the recommended testing interval, a full preventive test according to industry standards must be completed before putting the cable back into service.