Shielded cable in each phase of conductor insulation is winding and a semiconductor layer or shield of conductive material qualitative make it, the shielding layer and ground wire attached again, therefore, whenever trauma and damage of the cable core insulation, conductive shield conductor must first contact, again through the conductive shield, ground conductor leakage relay protection operation, on its own to cut off the power supply.
Thus shielded cable would have played an important role in advance to cut off the power supply.
Avoid cable interphase short circuit accidents, also can avoid personal electric shock, and reduce the risk of coal dust and gas explosion caused by a spark.
Monitor type of shielded cable: in addition to meeting the requirements of shielded cable structure, cable line, and a monitoring or monitoring layer.
Monitoring line by double-sided conductive adhesive tape or conductive rubber and tin plating, silk is also useful to copper, mixed woven wire, set in the main conductor and the outer layer of the earth, between monitoring layer and ground wire with insulation layer, as a result, monitoring type cable belongs to insulation monitoring type cable, also called double shielded cable.
We choose the coal-winning machine cable belonging to this kind of cable.
Pay attention to question 1) for connection to the shielded cable shielding layer of the main conductor outside carefully handled, especially after a conductive adhesive tape stripping, want to use wood file or carbon tetrachloride solvent will stick to the insulating layer on the surface of the conductive adhesive or graphite powder processing clean.2) shield and other idle line core must be reliable grounding.3) shielding layer and the conductive exposed part of the air clearance must satisfy the rated voltage 660 v, the minimum air gap 10 mm.
Rated voltage 1140 v, the minimum air gap 18 mm.4) shielding layer and creepage distance between phase conductor bare conductors must satisfy the rated voltage 660 v, the minimum creepage distance 37.5 ~ 50 mm.
Rated voltage 1140 v, the minimum creepage distance 67.5 ~ 90 mm. Cable selection, pay attention to the problem and the commonly used specifications