Five main reasons and protection knowledge
The insulation layer of a cable is a crucial barrier to ensure the safe operation of power lines. Once it fails, it can lead to leakage, short circuits, tripping, and even fire accidents. Cable insulation failure rarely occurs suddenly; it is mostly caused by long-term cumulative factors such as electric fields, high temperatures, mechanical external forces, environmental corrosion, and construction process defects. This article explains the main reasons for insulation failure and protection methods in a simple and popular way.
1. Electrical stress aging: Invisible electric field erosion
Cables operate under electricity for a long time, and tiny bubbles, impurities, and conductor burrs inside the insulation can cause local electric field concentration, resulting in local discharge. This weak discharge is invisible to the naked eye but will continuously damage the molecular structure of the insulation material, gradually forming carbonized conductive channels. Over time, the insulation performance continuously declines, eventually causing breakdown and short circuits. In addition, lightning strikes and instantaneous overvoltages generated by switch operations can easily break through the weak insulation positions, causing sudden failures.
2. Thermal stress aging: High temperature significantly shortens cable lifespan
Overloaded operation, dense stacking, and poor heat dissipation can lead to temperature increases. Insulation plastics are high-molecular materials that are most afraid of continuous high temperatures. Industry rules show that for every 8-10℃ increase in temperature, the cable's lifespan is directly halved. High temperatures will make the insulation harden, become brittle, and crack, reducing insulation resistance. Repeated alternating cold and hot conditions will aggravate material fatigue, and thermal aging is irreversible, and the damaged insulation cannot recover on its own.
3. Mechanical damage: The most common construction and operation hazards
During cable laying, excessive bending, pulling, rolling, backfilling with crushed stones, and long-term vibration and settlement can cause tiny cracks in the insulation layer. There are no obvious faults initially, but water vapor and air will slowly seep into the cracks, triggering moisture absorption, discharge aging. The stress concentration at cable joints and terminal positions is a weak point where insulation damage and faults are prone to occur.
4. Environmental corrosion: Long-term wear and tear from the external environment
In damp underground environments, the cable sheath will absorb water, causing insulation moisture absorption, leakage, and layer-by-layer aging; in outdoor areas, ultraviolet rays from sunlight will cause the outer skin to flake, crack, and harden, and the insulation capacity will gradually decline. In chemical, salt, and alkaline areas, acids, oils, and corrosive gases will directly damage the insulation structure, causing permanent aging and failure.
5. Material and process defects: Inherent deficiencies, premature aging
Low-quality cable raw materials are not pure, the insulation thickness is uneven, and there are many internal bubbles. The cable itself has poor pressure resistance and aging resistance. On-site construction is not standardized, such as rough joint fabrication, cutting damage to the insulation, poor sealing, and inadequate waterproofing, which are the main causes of on-site failures. Industry statistics show that over 60% of cable insulation failures occur at joint positions.
6. Simple and Effective Protection Measures
To extend the lifespan of cables and reduce insulation failures, simply focus on the following five key points: select compliant and qualified cables and use them in the appropriate environment; standardize the laying process, avoid mechanical damage, and meticulously seal the joints; strictly prohibit long-term overloading operation to ensure smooth heat dissipation of the lines; implement waterproof, sun protection, and anti-corrosion protection for outdoor and underground cables; conduct regular insulation tests, infrared temperature measurements, and partial discharge detections to identify potential aging issues in advance.
