In our country, the current plug-in devices used in the high voltage cable adapter box are divided into two major series European style and American style. European devices are the outdoor box substation cable connection concept introduced from Europe in the 1980s to the field of cable branch box, American devices are introduced from the United States in the 1990s to the installation of box substation concept into the cable distribution box.

1. Differences between European devices and American devices

There is no clearly defined line between European style and American style devices, and the understanding of insiders in our country is also inconsistent. They are slightly different in performance and price, so it is of great significance to know the difference.

1.1 The insulation structure of the device is different

American device conductive body outside has three layers of rubber surrounded, the innermost layer is a semi-conductive shielding layer, the middle layer is the main insulation layer, the outermost for constant grounding semi-conductive shielding layer, so it is called shielding type, the price is slightly higher. European-style devices are coated with two layers of rubber and have no outermost layer.

1.2 Different ideas of branch circuit connection

European devices use series branches, that is, a number of silicon rubber insulated T-devices from the direction of the short arm one by one in series connected to form the main circuit, and from the long arm of each T leads to branches. There are some disadvantages in this series branch mode: if a branch of T is faulty, the series component must be unlocked, and the faulty T component can be dismantled and reassembled before it can continue to run. Once the fault is handled, the component needs to be disassembled and reassembled again, which is troublesome. The main circuit has many series joints, which affects the conductive reliability and reduces the dynamic stability. When there are more serial components, the axis is difficult to keep in the same straight line, resulting in some joint interface deviated from the normal position, the interface insulation strength and anti-seepage capacity will be reduced.

American devices use parallel branches to overcome the disadvantages of series branches. The parallel branch is a set of (three-phase) insulation devices called bus board fixed on the wall of the distribution box, which acts as a busbar. There are a number of external cone-type connecting seats in parallel on the bus board, and all cables, such as incoming lines, outgoing lines and branch lines, are connected to the bus board. The conductive body inside the bus board is silver welded, which is reliable. However, the distance between the three phases is large, which makes it slightly difficult for the phase cable to be connected. Moreover, the three phases of the bus board arranged in a row will increase the length and size of the box.

1.3 The taper of the matching surface is different

European taper according to the German standard DIN47636 design, taper is small; American taper is designed in accordance with the American standard IEEE386, slightly larger taper. The difference of taper will bring the following two differences:

a) Surface insulation strength of bonding interface between devices is different. Combined with the interfacial insulation strength and its compression rebound force, the silicone rubber has a very high elasticity, the tighter the compression, the higher the insulation strength. If the taper is large, the rebound force will be large and the insulation strength will be high. Therefore, the interface insulation strength of the American style is larger than that of the European style.

b) Different anti-seepage capacity. The larger the taper, the tighter the interface rubber material is pressed, the better the waterproof performance. Therefore, the anti-seepage performance of American devices is slightly better than that of European devices.

4, European devices and American devices to distinguish the principle

In the domestic production of plug-in devices, some manufacturers will be the European and American structure mixed with each other, it is difficult to distinguish. Here are three basic concepts that will help us decide:

a) From the point of view of the branch structure of the plug-in device, the parallel branches are American cable branch boxes, and the series branches are European cable branch boxes.

b) From the perspective of insulation structure, the device with three layers of rubber (inner shield layer, main insulation layer, outer shield layer) is American, and the device with two layers of rubber (inner shield layer, main insulation layer) is European. As for those in the outer surface of two layers of rubber using spraying method to cover a layer of semi-conductive film devices, because in the installation or use process of semi-conductive thin layer is easy to be worn off, unreliable grounding performance, can not be considered as a shield type, should still belong to European devices.

c) The size of the taper of the device with the taper surface cannot be used as a basis for discrimination. Because the size of the taper is only a geometric size problem, only involves insulation strength and anti-soaking ability, whether European or American insulation devices, its taper can be designed according to the American standard or German standard, so that there will be American taper, American taper, European taper and European taper and other different types of devices.