High voltage cable failure

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High voltage cables are important given their role in power transmission and distribution. Wen cables fail it results in power blackouts that are not only inconvenient but also disruptive. Life savings functions disrupted in hospitals can cause fatalities and disrupted production processes in factories can cause costly losses in time and products that have to be discarded.

What does a HV cable consist of

In order to understand how failures in cables occur we need first to understand the the components of the HV cable from the inside to the outside. What is actually inside that cable? Well, we have a conductor, insulation, internal sheath, filler (armor) and external sheath. Armored high-voltage cable is mainly used for underground burial, which can resist high compression on the surface and prevent damage caused by other external forces.

HV cables can fail either as a result of the manufacturers shortcomings or due to the installation. It is therefore critical to ensure that you buy your cables from a reputable manufacturer who adheres to the highest standards. There are cheap cables available in the market today but be sure that going for the cheaper options can result in expensive failures in the long run. Causes of cable failure can be either due to poor cable quality which is as a result of the production process or due to poor installation process.

Poor cable production

When it comes to cables failure can occur due to the cable body, cable joint or cable grounding system. Let us examine the three and get to understand what it means. Problems with the cable body can occur due to poor cable production processes which result in insulation eccentricity, uneven insulation shield thickness, impurities in the insulation, protrusion on the inner and outer shield layer, uneven crosslinking, damp cable, poor sealing, cable metal sheath, etc. In some cases, failure may occur during completed testing or shortly after commissioning. Most of them exist in the form of defects in the cable system, which will cause serious hidden danger to the long-term use and safe operation of the cable. system failure due to poor quality installation work

Cable manufacturing is normally done in a controlled environemtn which is more than you can say for site conditions where humidity, temperature, dust and moisture are at the mercy of the environment. If these conditions are extreme it can put the cables at risk.

In addition to this it is inevitable that during installation on site, small slip marks will be left on the insulating surface during cable installation. The semi-conductive particles and sand on the emery cloth can also be embedded in the insulator. In addition, since the insulation material is exposed to the air during the joint construction process, the insulation material can also suck in moisture, which can have long term dire consequences.

Other problems that can cause cable failure during installation include failure to follow manufacturers installation instructions as well as improper sealing treatment. The intermediate joint must use a metal copper shell, PE or PVC insulating anticorrosive layer sealing structure to ensure the air tightness of the lead seal on site, and effectively ensure the sealing and waterproof performance of the joint. All in all when it comes to cable failure the most prevalent cause of failure is poor quality or even the use of counterfeit cables which put property and lives at risk and so before anything else ensure that you buy quality certified cable from a reliable supplier.

Cable Joint Defects

Like all joints in structures, high-voltage cable joints are also a weak link in the chain. This is because of air gaps in the tape layer or impurities that find themselves between the insulation layers.

There are two types of cable joints cable teminal joints and middle terminal cable joints. Regardless of the type of joint, cable joint failure usually occurs where the cable insulation shield is broken, because this is where the electrical stress is concentrated, and the cause of cable joint failure due to manufacturing reasons is stress. There are also cone manufacturing defects, insulation packing problems, leakage of sealing ring, etc

Cable Grounding System

The cable grounding system includes the cable grounding box, the cable grounding protection box (with protective layer), the cable cross interconnection box, and the protective layer protector. Generally speaking, the problems that are prone to occur here are mainly due to the poor sealing of the box and the water entering the ground, resulting in excessive current induced by the metal sheath. In addition, problems include unreasonable selection of parameters or poor quality of the protective layer protector. Also bear in mind that unstable zinc oxide crystals can easily damage the protective layer.