The strength of the cross-linked insulation layer is relatively high

The strength of the cross-linked insulation layer is relatively high. The construction personnel pressed enough to press the pits according to the requirements, and the effect is uncertain. The main reasons for insufficient conductor connection pressure are the following 3 points.Due to the large number of types, forms and specifications of cable accessories; uneven quality; different technical levels of construction personnel; different operating modes and conditions of cable joints, the reasons for the failure of cross-linked cable joints are different. Conductor damage. 

The operation proved that when the contact surface of the crimping tool and the wire is cleaner, when the temperature of the joint increases, the oxide film produced is thinner and the contact resistance is smaller. The normal working temperature of J-20 rubber self-adhesive tape does not exceed 75℃; J-30 only reaches 90℃; the use condition of heat shrinkable material is -50～100℃. Such a vicious circle destroys the insulating layer of the joint, forms a short circuit between phases, and causes an explosion and burns.

 Under normal conditions, it will run seriously and generate heat and load slightly. The reasons for the increase in contact resistance are as follows. brass valve The connection fittings have large gaps. Because the allowable current-carrying capacity of YJV22-3×150 cross-linked cable is 476A; while the allowable current-carrying capacity of ZQ2-3×240 oil-paper cable is 420A, which also exceeds 56A. Due to the different media of cross-linked cables and oil-paper cables, the causes of joint failures are very different.

The main reason for the heating of the connection (crimping, welding and mechanical connection), in addition to the equipment and material performance factors, the key is the process technology and sense of responsibility. In recent years, there are many manufacturers of crimping machine tools, management is chaotic, and there is no unified standard, especially the mechanical crimping pliers produced in recent years.