The laying of large pair-count communication cables refers to the routing methods of the cables after exiting the distribution box to reach the electrical equipment or another distribution box. This may include concealed installations along the ground, walls, or ceiling, as well as exposed installations. Common methods include routing through bridges, cable trays, cable trenches, and conduits, with the appropriate cable laying method chosen based on different environments, conditions, and properties. The direct cause of aging and failure in large pair-count communication cables is the reduction in insulation and subsequent breakdown. Many factors can lead to a decrease in cable insulation, and based on practical operating experience, the following situations are summarized.
Exterior Force Damage
Over the past few years, analysis has shown that, especially in today's era of rapid economic growth, a significant number of cable failures are caused by mechanical damage.
2. Insulation moisture absorption
This situation is quite common, typically occurring at cable joints within buried or conduit installations. For instance, poor-quality cable joint fabrication or making joints under humid climatic conditions can lead to water ingress or the presence of steam, which, over time, under the influence of the electric field, forms water trees. This gradually weakens the cable's insulation integrity, resulting in faults.
3. Chemical Corrosion
Cables buried directly in areas with acidic or alkaline effects often suffer corrosion of their armor, lead sheath, or outer sheath. The protective layer, subjected to long-term chemical or electrolytic corrosion, becomes ineffective, leading to reduced insulation and cable failures. When a failure occurs, the level of cable corrosion is often quite severe by that time.
4. Ongoing Overload Operation
Overload operation inevitably leads to conductor heating as the load current passes through the cable due to the thermal effect of current. Simultaneously, the skin effect of charges, the eddy current losses of the steel sheath, and the dielectric losses also generate additional heat, causing the cable temperature to rise. Prolonged overload operation accelerates the aging of the insulation due to the high temperature, eventually leading to insulation breakdown. Particularly during the hot summer months, the temperature rise of the cable often results in the first breakdown at the weakest points of the cable insulation, thus resulting in a higher number of cable faults during the summer.
5. Cable joint failure
Cable joints are the weakest link in cable lines, and failures caused by direct human error (poor construction) are all too common. During the process of making cable joints, if issues such as loose connections or inadequate heating occur, it can lead to reduced insulation of the cable head, thereby triggering accidents.
6. Environment and Temperature
The external environment and heat sources surrounding the cable can also cause the cable to overheat, lead to insulation breakdown, and even result in explosions and fires.
7. Other Factors
Normal aging of the cable core or due to natural disasters and other causes.
