Cable entry boxes on high-voltage equipment for mechanical fastening of cable entries and electrical transitions to transformer or GIS combination appliances. The epoxy sleeve of the cable termination effectively prevents the insulating oil or SF6 gas in the inlet bin from penetrating into the cable body. In order to solve the problem of electrical insulation of the cable termination head in the epoxy casing cavity, the conventional solution is to fill the casing cavity with oil or charge SF6 gas. The equipment terminal of such high-voltage cable is called oil-filled (or inflated). ) type, also known as wet type. The method of inflating is less used, and it is generally oil-filled.
The oil-filled wet equipment terminal must complete the electrical and mechanical connection and installation with the cable entry warehouse on site. In the field test and installation work, the high-voltage equipment factory personnel are required to complete the charging and deflation of the cable entry warehouse. (oil) and other work, the work process is more troublesome. Some oil-filled terminals should be attached with a respirator (having a transformer-like oil pillow function); some also need to use vacuum to achieve oil injection into the epoxy casing, which is very inconvenient. The picture below shows an oil-filled 110kV cable termination to be assembled on a GIS combination.
Another type of high-voltage cable terminal realizes the gapless contact between the cable end head stress cone and the inner wall of the epoxy resin sleeve and the ideal distribution of the power line through the optimized structural design, without filling the epoxy casing with oil (gas In the case of a good solution to the problem of electrical insulation in the casing cavity, such equipment terminals are called dry terminals. The dry high-voltage cable terminal realizes oil-free and fully enclosed, so the position of the cable terminal is not limited, and the connection between the cable and the GIS combination appliance or transformer can be flexibly realized in different directions according to the needs of the site. The following figure shows the dry cable termination assembled from the lower part of the cable entry compartment on the side of the transformer.
Dry cable termination from the lower part of the cable entry compartment located on the side of the transformer. According to the assembly characteristics of dry high voltage cable terminals, they can be divided into three categories.
The first type is the conventional type, that is, the epoxy bushing and the cable and the stress cone are integrally installed and tested. The installation procedure in the field is almost the same as that of the wet terminal, except that the casing is not filled with oil (gas). In the field test and installation work, the high-voltage equipment factory personnel are still required to complete the charging and deflation (oil) work on the cable entry warehouse. The overall installation work and cross-operation are quite cumbersome.
The second type is plug-in type. The epoxy casing of this type of cable termination can be installed separately from the cable and the stress cone, but it cannot be tested separately. A spring locking device is mounted on the conductive rod of the cable core. When the cable head is inserted into the epoxy sleeve, the spring locking device automatically pops out, and the cable head is locked in the epoxy sleeve to ensure that it does not slip. . The cable ends of such cable terminations cannot be pulled out once inserted. The installation procedure of the plug-in cable terminal is basically the same as that of the first type. For example, for the GIS combination electric appliance, the epoxy resin sleeve can be installed in the factory to the cable entry box of the GIS in advance, and the epoxy sleeve can completely carry the cable. The SF6 gas in the incoming warehouse is isolated from the outside, which reduces the workload on site. However, when the cable needs to be processed during the test, it is still necessary to charge and discharge the gas in the cable entry bin. In addition, when the plug-in cable terminal is used in a transformer, the installation and test are the same as those of the conventional type 1 cable terminal.
The third type is the plug-in cable terminal. The bushing can be installed separately from the cable and the stress cone, or it can be tested separately; the cable cable head can be inserted or pulled out. Its structure is the simplest and the installation is the easiest. Pluggable cable terminations are also classified into reusable and non-reusable. The components of the cable end plug can be removed from the reassembled cable termination, which is called a reusable plug-in cable termination, otherwise it is a non-reusable plug-in cable termination.