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Improvement of stress cone for Stress Control Tube

2022-05-18
High voltage cable termination installed in the stress ball capacitor cone or capacitor cake to ease the intensity of the power line has achieved successful experience, as is known to all, without the above control of electric field stress device, will be close to the grounding shield end, free discharge, thus shortening the life of the cable termination. The time of terminal damage depends on the strength of the electric field at the end of the shielding layer and the anti-ionization performance of the insulating material, generally within a year. The function of the heat shrinkable Stress Control Tube is to evacuate the electrical stress at the outer shield cut at the end of the 10-35kV crosslinked power cable.

So the electric stress control of stress control tube is a very important part in the design of middle and high voltage cable accessories. Electric stress control is to control the electric field distribution and electric field intensity inside the cable accessories, that is, to take appropriate measures to make the electric field distribution and electric field intensity in the best state, so as to improve the reliability and service life of the cable accessories. For the cable terminal, the electric field distortion is the most serious, which affects the reliability of terminal operation the most is the outer shield cut, while the electric field distortion of the middle connector of the cable not only affects the outer shield cut, but also affects the insulation cut of the cable end.

The material composition of heat shrinkable stress control tube is made up of a variety of polymer materials blending or copolymerization, the general base material is polar polymer, and then add high dielectric constant filler and so on. The heat shrinkable stress control tube in cable accessories is mainly used to relieve the electrical stress at the outer shielding cut of the shielding end of dispersed cross-linked power cable.

Traditional measures of control stress is in the end of the shield, with insulating tape, paper roll or molding material, on the cable insulation around the package or add a cone olive shape, such as shielding layer outside at the end of the cable insulation layer thickness increases, so the electric field distribution is uniform, the deficiency of the stress cone is must enlarge the diameter of cable terminal, This and power equipment tend to miniaturize, quite disproportionate. In addition, it is time-consuming to wrap the stress cone by hand, and the prefabricated molded stress cone lacks versatility. For this reason, after the 1970s, an innovative control stress with semiconductor rubber belt has been successfully studied, and then developed a thermal shrinkage nonlinear semiconductor rubber stress tube, to achieve the requirements of small volume, simple construction. All over the world, this kind of semiconductor material is widely used as a new stress control device in the cable terminals of kilovolt and below, especially in the accessories of rubber and plastic and non-drip cable.

The requirement of stress control tube for stress layer material is that it should be stable even in the presence of different electric field intensity and due to conductor or ambient temperature changes. The life of cable accessories is also the same as the cable body, not simply through the above several tests, can make a reliable judgment, the most effective measure is the same as the cable, need to pass the load cycle test.


stress control tube


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