Why can't a 10-kilovolt cable that has been

YouTube：https://youtube.com/shorts/_TS1MPCCbvU

Why can't a 10-kilovolt cable that has been in use for 5 years be powered on after power-off maintenance?

The inability to power on a 10-kilovolt cable that has been in use for 5 years after power-off maintenance may be caused by various reasons, including problems with the cable itself, construction and connection issues, equipment matching problems, and external environmental influences. The following is a detailed analysis:

### Problems with the Cable Itself
- **Insulation Aging**: Since the cable has been in use for 5 years, there may be aging and damage to the insulation layer. Even after maintenance, it is difficult to fully restore its insulation performance. When power is supplied, it may be broken down due to insufficient insulation strength, resulting in failure to supply power normally.
- **Internal Damage**: During long-term use, due to factors such as mechanical stress and thermal stress, the internal conductors of the cable may break or become loose, or there may be hidden damages such as air gaps and cracks in the insulation layer. These problems may not be detected during maintenance, and will trigger failures when power is supplied.
- **Cable Moisture Ingress**: If the terminations and intermediate joints of the cable are not well sealed, or the outer sheath of the cable is damaged, there may still be a risk of moisture ingress after maintenance. Moisture will reduce the insulation performance, leading to the inability to supply power.

### Construction and Connection Issues
- **Improper Construction**: During the power-off maintenance process, construction personnel may make operational errors, such as excessive bending and stretching of the cable, causing damage to the internal structure of the cable. Or when installing cable accessories, the process is not standardized, for example, the production of cable heads does not meet the requirements, resulting in problems such as poor contact and poor insulation.
- **Connection Point Problems**: The connection points between the cable and equipment such as switchgear and transformers may not be tightened properly after maintenance, resulting in looseness. When power is supplied, problems such as heating and arcing will occur, which will affect power supply.

### Equipment Matching Problems
- **Switchgear Failures**: Equipment such as circuit breakers and isolating switches inside the switchgear may malfunction after maintenance. For example, the circuit breaker cannot be closed normally, and the isolating switch has poor contact, etc., resulting in the inability to supply power to the cable.
- **Malfunction of Protection Devices**: The relay protection devices of the cable may malfunction after maintenance. For example, the setting value is wrongly set, or the protection device itself is faulty. When power is supplied, the protection device mistakenly thinks that a fault has occurred and trips, resulting in the inability to supply power normally.

### External Environmental Influences
- **External Force Damage**: After maintenance, the cable may be damaged by external forces, such as being dug up or smashed. Especially near some construction sites, the cable route is likely to be accidentally touched.
- **Influence of Environmental Changes**: If there are significant changes in the environmental humidity, temperature, and other conditions where the cable is located, it may affect the performance of the cable. For example, in a humid environment, the insulation performance of the cable will decrease, resulting in difficulties in power supply.

The reasons for the inability to power on a 10-kilovolt cable after power-off maintenance are relatively complex. It is necessary to use professional testing equipment and technical means, such as insulation resistance testing, withstand voltage testing, cable fault location, etc., to conduct a comprehensive inspection of the cable and related equipment, so as to accurately identify the cause of the fault and carry out repairs.