Flame-retardant cables may have some faults when they are in use, such as cable breakdown, cable conductor damage, broken cores and other faults. The conductor of the flame-retardant cable has a small cross-sectional area, and may be broken during the production of the cable or during the extrusion process. So how to check the disconnection of flame retardant cable?
One: the method of energizing the capacitor
Some cable factories usually use capacitance comparison method to find the approximate location of the disconnection. Using continuous power-on method to accurately determine the disconnection point of the cable, the efficiency of this method is very low. Generally, it takes about 1 and a half hours to find a disconnection point. With this method, it is almost impossible to find a broken core for flame-retardant cables whose shielding, armoring, and sheathing processes have been completed. If it is not done properly, the flame-retardant cable will be scrapped. This method is basically no longer needed.
2: Combination of capacitance method and induction method
This method is used for the broken core of the cable core, which requires that the cable core has no metal layer and no extruded sheath. When searching, first use the capacitor to find the approximate location of the cable disconnection, and then use the induced voltage method to accurately find the disconnection point. This method is very simple and quick, and it is also the most used method at present. The induction voltage method is to connect the 650V AC voltage at one end of the broken core of the cable, and the other end and other cores are grounded, and then test with a sensor pen that can emit light signals. The signal will change, so you can accurately find the cable break point.
Three: Combination of constant current source and bridge method
This method is used for finished cables or cable cores that have been coated with a metal layer. Use is to find the method is to burn the insulation at the broken core of the flame-retardant cable with a constant current source, and then use the bridge method fault locator to accurately locate the fault point, which is also a frequently used method.