At present, according to the main insulation molding process, the commonly used 35kV and below cable terminals and intermediate joints can be divided into four commonly used product types: winding type, heat shrinkable type, cold shrinkable type and prefabricated type.
There are also cast and detachable cable accessories for specific product ranges.
Wrapping type cable accessories are cable accessories that are made by wrapping insulation and shielding with strips. The stress control mode adopts stress cone or stress control belt with high dielectric constant, which requires higher technical level of construction personnel, and the construction technology is more complex, and has been gradually eliminated on site.
Based on the principle of "elastic memory" effect of polymer, thermal shrinkable sleeve, branch sleeve, rain skirt and other thermal shrinkable prefabricated parts are developed in thermal shrinkable cable accessories, which can be heated at the end or joint of the treated cable according to the program.
Heat-shrinkable cable accessories are simple in technology, low in price and easy to maintain.
But there are also some problems, such as shortened service life caused by the inevitable "respiration" caused by environmental temperature change, which affects the reliability of power supply.
The engineering application of cold shrink cable accessories tube and other cold contraction fabrication, silicone rubber or epdm as the main raw material, after specially formulated synthetic pre expansion in the screw core support, install and use, without any external heat source, as long as open support conductor will shrink, and tight in the required position.
The cold-shrinkable cable accessories are required to be used within the specified period of service, and the price is relatively high.
Prefabricated cable accessories make use of rubber material to make the reinforced insulation and semi-conductive shield layer in the cable accessories into a whole or a number of parts in the factory mold. The cable accessories formed by the on-site package at the treated cable end or middle joint are called prefabricated cable accessories.
Prefabricated cable accessories can be carried out in the factory for the corresponding factory routine test, further improve the operation reliability of the cable terminal, but also greatly reduce the site installation workload.
In terms of structure, the cold-shrink cable accessories and prefabricated cable accessories are basically the same, but there are some differences in material performance and treatment.
Casting cable accessories are made of thermosetting resin, which is poured on site into the treated mold or box at the cable end or joint and solidified into cable accessories.
It is especially suitable for interconnecting plastic extruded insulated cable and paper impregnated insulated cable.
Separable Connector a fully insulated cable accessory, such as a terminal, connector, or branch connector, that allows cables and other equipment to be connected or disconnected from the cable.
Separable connector is mainly used for equipment such as fully sealed switch cabinet, inflatable ring network unit, cable branch box, etc. It can be regarded as a new type of cable terminal.
And more use of prefabricated terminal structure.