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Introduction to the Structure Principle and Main Points of Cable Accessories

Pulished on Feb. 29, 2020


Overhead power line fitting is an indispensable part of the cable line. The cable cannot work without accessories. The power transmission task is completed by the cable line as a whole consisting of cables and accessories. It can be said that the cable accessory is a continuation of the cable function. The requirements of the cable body, such as the section and surface characteristics of the conductor, the semi-conductive layer, the metal shielding layer, the insulation layer and the sheath, etc. also apply to the cable accessories, especially the intermediate joints, that is, each of the intermediate joints Parts should correspond to all parts of the cable. The terminals are basically the same, except that the external insulation is special.

In addition, the accessory has more requirements than the cable body, because its structure is more complex and its weaknesses are more. It is also technically more difficult. There are:

● Conductor connection technology (that is, the problem of thermal field)

● Treatment technology for local concentration of electric field (stress)

● Longitudinal insulation (electrical strength / climbing distance)

● Sealing technology

Suspension Clamp

Suspension Clamp

Cable joint and terminal structure principle introduction

Basic points of cable fitting accessories technology:

1) Considering the electric field distribution and its improvement measures (ie, structural design), the main technique for improving the electric field distribution is to deal with the stress concentration problems appearing on the attachment. The main methods are:

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

b. Electrical parameter method, increasing the dielectric constant and surface capacitance of the surrounding medium, that is, the stress tube structure;

c. Method of combining geometric structure and electrical parameters.

2) Consider from improving the dielectric strength of the insulation (ie selection and improvement of materials). The main technologies are:

a. Eliminate the parts where air gaps and impurities may appear, especially the impurities and air gaps at the interface between two insulating materials, and replace materials with low electric strength with high electric strength, such as filling the air gap with silicone grease.

b. Increase the pressure at the interface between the two insulating materials to increase the electrical strength.

c. Use a semi-conductive shield to shield the air gap from the working field strength, and also improve the surface electric field distribution.

4. Precautions for power cable stripping

Stripping dimensions of outer sheath, steel armor, inner sheath, copper shield, outer semiconducting.

Stripping the outer semiconducting layer of the cable is the key to successfully installing accessories.

The sandpaper used for the insulation layer grinding must be insulated sandpaper (abrasive particles are silicon dioxide). Remember to grind in the radial direction.

Keep the cable filler of the intermediate connector as far as possible and fill it back.

The entire process of handling the insulation layer must be clean and clean, and every effort must be made to avoid any impurities from sticking to the surface of the insulation layer.