Design of Conductor Shielding Layer of Rubber-sheathed Cable for Mine

The conductor shielding layer mainly plays the role of improving the electric field structure in the aac cable, preventing discharge caused by the tip protrusion on the surface of the conductor, reducing the amount of partial discharge, and ensuring the service life and reliability of the cable. Recently, in the GB12972–91 and MT818–1999 standards, there are rubber-sheathed cables with voltage level 3.6/6kV for mining, and the requirements for acsr conductor shielding are put forward for the rubber-sheathed cables of this voltage level. The shielding layer must be extruded. Way to proceed. According to this requirement, the 6/10kV mining rubber-sheathed cable must also have a conductor shielding layer to ensure the safe operation of the cable.

The conductor shielding layer of the rubber cable shall be processed with semi-conductive rubber material. The aaac conductor shielding layer is produced by wrapping and squeezing methods. The shielding layer produced by the squeezing method is smoother than that produced by the wrapping method and has no protrusions, which facilitates the improvement of the uniform electric field effect. The selection of the thickness of the conductor shielding layer comes from two requirements: one is to ensure that the surface of the conductor shielding layer after squeezing is smooth. Because the mining rubber-sheathed cable generally adopts the method of thin copper wire stranded wire, it is not It may be pressed tightly, and there is a certain degree of twisting on the twisted surface of the wire. These unevennesses do not have much impact on the electrical performance of the low-voltage cable, but for the high-voltage cable, it just causes the uneven electric field strength, which can only be relied on. Squeeze or wrap the conductor shielding layer to eliminate its influence, but the thickness of the conductor shielding layer is too thin to be achieved in the process;

In addition, from an economic point of view, although the thickening of the conductor shielding layer is relatively easy to achieve in the process, every increase of 1mm in the insulation thickness of the cable will increase the cable outer diameter of the cable by 4.3mm. The use of protective layer materials has increased dramatically, which has brought about a substantial increase in the cost of cable manufacturing. In the GB12972–91 and MT818–1999 standards, it is proposed that “the calculated thickness of the semi-conductive layer should be controlled at about 0.7mm, and the actual thickness will not be assessed.” Based on the above two factors, it is appropriate to adopt these two standards and the consistent thickness of the conductor shielding layer. With reference to this requirement, 6/10kV mining rubber-sheathed cables have also proposed a technical requirement that the calculated thickness of the conductor shielding layer is controlled at 0.7mm, and the actual production thickness is also controlled according to 0.7mm, but it is not controlled as a rigid quality indicator.