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Cable Accessories Principle
Nov 02, 2017

Power cable accessories are connecting cable and transmission and distribution lines and related distribution equipment products, generally refers to cable line in the middle of the cable connection and terminal connections, it with the cable together form the electricity transmission network; Cable accessories are mainly based on the characteristics of cable structure, which can restore the performance of the cable and guarantee the extension of cable length and the terminal connection. The reliability of high voltage cable accessories can be judged from the aspects of electrical performance, sealing moisture resistance, mechanical properties and process performance.

The connection method

General component is attachment cable connection terminal connection and connection among them, the terminal connection is divided into indoor and outdoor terminal, usually outdoor terminal is to point to the outdoor cable joint, indoor terminal refers to the joint interior connection cables and electrical equipment; The intermediate connection is divided into straight and insulated types.

There are many kinds of cable accessories,

There are different types of characteristics and limitations, and they cannot be replaced by one another. The common ones are as follows:

(1) wrapping: the attached cable accessories made of rubber strip (self-adhesive) are wrapped in the enclosed cable accessories, which are easy to release, less resistant to fire and short life;

(2) water: water at the scene with thermosetting resin as the main material, the selected material with epoxy resin, polyurethane, acrylic resin, etc., the attachment during the curing reaction of the fatal drawback is easy to produce bubbles;

(3) molding type: mainly used in the middle connection of cables, with the addition of mold and temperature at the site, which is integrated with the cable. The process of the attachment is complicated and the time is long, and it is not suitable for terminal connector;

(4) cold shrink: the elastomers, such as silicone rubber and tri-propylene rubber, are pre-expanded in the factory and then formed by adding plastic supporting strips. Construction at the scene, the article drew support make the pipe under the rubber elastic effect of inherent ling shrinkage on the cable and cable accessories The attachment is best suited for cannot use flame heating construction sites, such as mining, oil chemical industry, etc.;

(5) thermal contraction: the rubber - plastic alloy is made into a "shape memory effect different component products, in the field heating shrinkage on the cable and made of the attachment. The attachment is characterized by light weight, simple construction, reliable operation and low price.

(6) prefabrication: using silicone rubber to inject into different components, one sulfide molding, retaining the contact interface only, and inserting the cable when the site is constructed. The construction process will be unpredictable adverse factors in the environment to reduce to the lowest degree, so the attachment has huge potential use value, is the development direction of crosslinking cable accessories, but manufacturing technology difficulty is high, involving a variety of disciplines and industries. Prefabricated accessories are still used in the installation materials of the three forklift and the shielding of the cable, so they are actually prefabricated and heat-shrinkable.

The factors of the quality of cable accessories are multivariate, which in principle have the following aspects:

1. Electrical performance. The quality of electrical performance is the first principle to judge the quality of cable accessories. It mainly considers whether the electric field distribution of cable accessories is reasonable, whether the measures to improve the distribution of electric field are appropriate, the electrical strength of the material, the dielectric loss and the insulation margin of the product. At the same time, also must consider the stability of performance, including chemical and physical properties of the cable accessories material and structure stability, the stress control material performance is stable, for example, the stress cone is easy to deformation, cable insulation retraction of the distribution of electric field of cable accessories and measures to prevent the influence of compatibility of various materials with combined interface performance stability, etc. In addition, also should consider the thermal performance of cable accessories, such as dielectric loss, contact resistance of the conductor connection and its stability, release of heat conduction, heat bilges cold shrink effect the performance of the electrical and mechanical components, etc.

2. Sealing performance. The seal moisture-proof performance directly affects the electrical performance and service life of cable accessories. The sealing structure of the terminal is reliable and stable. In general, intermediate joints should also have a matching metal moisture-proof housing, especially in wet environments.

3. Mechanical properties. The terminal should have sufficient anti-bending and shockproof capability. Intermediate joints should be able to withstand a certain amount of tension and prevent damage from external forces.

4. Process performance. The process performance is an important condition for the design and selection of cable accessories, and the installation process should be as simple as possible, so as to facilitate site construction and short construction period. The requirements of the site environment and the technical level of the workers are not high; The installation quality is easy to control, reliable quality and so on.

5. Manufacturer's quality assurance system. Prefabricated type cable accessories factory, the factory is provided by the rubber casting, prefabricated stress cone, ceramic components, such as housing, impregnant and so on, at the scene when installation again assemble into whole terminal or joint, as a result, each of the parts manufacturing and installation process quality is directly related to the final product quality.

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