Structure principle and main points of cable accessories

Cable accessories are an essential part of the cable line, without accessories, the cable can not work. The transmission task is completed by the cable and accessories composed of the whole cable line. It can be said that cable accessories are a continuation of cable functions. 

The requirements for the cable body, such as the conductor section and surface characteristics, semi-conductive layer, metal shielding layer, insulation layer and protective layer, are also applicable to the cable accessories, especially the intermediate joint. That is, each part of the straight through joint needs to correspond to all parts of the cable. The termination is basically the same, except for the special insulation.In addition, the attachment has more requirements than the cable body, because its structure is complex, the technical difficulty is also greater, mainly the technology used:

1. Conductor connection technology (i.e., thermal field problem);

2. Processing technology of local concentration of electric field (stress);

3. Longitudinal insulation (interface electrical strength/outer climbing distance);

4. Sealing technology

Basic points of power cable accessories technology:

1. In terms of electric field distribution and its improvement measures (i.e. structural design), the main technology to improve electric field distribution is to solve the problem of stress concentration on the attachment. The main methods are:

a. Geometric structure method, increase the equivalent radius, namely stress cone structure;

b. Electrical parameter method, increase the dielectric constant and surface capacitance of the surrounding medium, namely the stress tube structure;

c. Combination of geometric structure and electrical parameters.

2. From the improvement of insulation electrical strength to consider (namely material selection and improvement).

a. Eliminate possible air gaps and impurities, especially the impurities and air gaps at the interface of the two insulating materials. Replace those with materials with high electrical strength, such as filling the air gaps with silicone grease.

b. Increase the pressure at the interface of the two insulating materials to improve the electrical strength.

c. Use a semi-conductive shield to shield the air gap beyond the working field intensity, and also cover the surface electric field distribution.