Controlling Details of the Eccentricity of XLPE Insulated Cable

Controlling the eccentricity of XLPE insulated cable can strengthen process quality control, stabilize production, reduce the occurrence frequency of unqualified products and increase the profit margin of the enterprise. So how to control the eccentricity effectively for a long time?

1. Wire drawing and stranding

The qualified products are not detected, but manufactured. Each department in the XLPE cable manufacturers has corresponding quality control responsibilities. Here we mainly talk about the conductor preparation and understanding of the tooling level as well as the detailed control.

When designing a conductor, people always give priority to or often only consider referring the current carrying capacity of the conductor and the direct current resistance of the conductor, which is not enough for power cables of 110kv and above. The roundness and straightness of the conductor often affect the distribution of the XLPE insulating material, which in turn affects the electric field distribution in the cable. The monofilament ductility of the conductor wire diameter will affect the cable insulation stress; the surface quality of the conductor (such as oxidation caused by improper storage, damage of the conductor in the circulation of the tool plate) also affects the current carrying capacity.

In the process of drawing, if the concentration and temperature of the emulsion are not regularly checked and replaced according to the standard, it is very likely to lead to monofilament oxidation in the process of drawing. The conductor must be fully protected during the conductor stranding process.

2. The preservation and scientific use of insulating materials (including insulation, conductor shielding, and insulating shielding)

There are strict requirements for the transportation, preservation and use of XLPE insulating materials. When storing XLPE cable materials, they should be uniformly arranged, and a special storage room for storing insulating materials and shielding materials should be established to prevent materials deterioration or abnormality caused by climate change. In addition, off-duty operators should be not allowed to enter and exit from the XLPE insulation storage room, shielding material storage room and cross-linking machine operation room as much as possible. When there are special circumstances, dust removal must be done to avoid cable breakdown caused by a single hair.

3. Process technology

At present, high-voltage cross-linking production lines are basically equipped with online derivometers, which can accurately monitor the eccentricity of cables online. The value measured by the derivometer is the insulation and shielding thickness at high temperature, while there are differences between the insulation and shielding thickness at high temperature or at normal temperature. It is worthwhile to study the relationship between the thickness, cross-linking temperature and speed of insulating materials of different batches from the same manufacturer.

The technical factors that affect the eccentricity of the cable insulation also include: the specifications of the extrusion die, the stress of the XLPE insulation material, the operating temperature and speed of the cross-linking machine, the skill level of the operators, and so on.

The one of the main issues that XLPE cable manufacturers need to pay attention to and think about is that how to stably produce qualified products that meet or exceed the eccentricity requirements specified by the standard. Details determine success or failure, a single strand of hair can destroy an entire cable or even an entire project.