The shielded cable is wrapped with a shielding layer made of semiconductor or conductive material outside the insulating layer of each phase core wire, and the shielding layer is tightly connected with the ground core wire. Therefore, the insulation of the cable core wire is damaged when the insulation is damaged. When the conductive core wire is in contact with the shielding layer, the leakage protection relay is protected by the conductive shielding layer and the ground core wire to cut off the power supply. Therefore, the shielded cable plays a role of cutting off the power in advance. To avoid short-circuit accidents between cables, it can also prevent personal electric shock and reduce the risk of coal dust and gas explosion caused by electric spark.
Surveillance shielded cable: In addition to meeting the shielded cable structure requirements, the cable also has a monitoring layer or monitoring line. Monitoring line consists of double-sided conductive tape or conductive rubber and tin plated wire
The composition is also made of copper and iron wire braided together, and is sheathed in the outer layer of the main core wire and the ground wire. An insulating layer is provided between the monitoring layer and the ground wire. Therefore, the monitoring cable belongs to the insulation monitoring cable. Double shielded cable. The shearer cable we chose belongs to this type of cable.
Be careful when connecting shielded cables
1) Carefully handle the shielding layer outside the main core wire, especially after the semi-conductive tape is stripped, use a solvent such as wood pulp or carbon tetrachloride to clean the conductive paste or graphite powder adhered to the surface of the insulation layer. .
2) The shield and other idle cores must be reliably grounded.
3) The air gap between the shielding layer and the conductive bare part must meet the rated voltage of 660v, and the minimum air gap is 10mm. When the rated voltage is 1140v, the minimum air gap is 18mm.
4) The creepage distance between the shielding layer and the bare conductor of the phase core must meet the rated voltage of 660v, and the minimum creepage distance is 37.5 to 50mm. When the rated voltage is 1140v, the minimum creepage distance is 67.5~90mm.
Cable selection, attention problems and common specifications
The "Coal Mine Safety Regulations" stipulates that mobile substations should use surveillance type shield rubber cable. 1140v equipment and 660v or 380v equipment for mining work surfaces must be phase shielded without flame retardant rubber cables. When the cable is selected, strict compliance with the "Coal Mine Safety Regulations" provisions.
Common rubber sleeve flexible cable specification: