Check the insulation performance of the cable and verify that the insulation properties of the supplier are stable. How to check the insulation of the cable?
For large-volume cable products, sampling inspection methods can be used to check the tensile strength, elongation at break, dielectric strength, volume resistivity, volume resistivity, oxygen index and density of the product.
Check the parameter data on the insulation package of the circuit. The national standard genuine circuit insulation package has clear indication: the name of the manufacturer, the type and name of the material, the date of manufacture, the net weight and the product certification. A guaranteed cable manufacturer can provide a product quality assurance certificate or quality inspection report to the user, and there must be a type test report on the statutory inspection department related to the cable insulation material. In normal supply, the cable manufacturer shall provide a type test report of the statutory inspection department for the current year.
Insulation of the cable is not only affected by the production process, but also reduces insulation due to improper transportation or directly causes insulation failure. In order to protect the insulation capacity of the cable during transportation and storage, the cable should not be exposed to the sun and rain to ensure complete packaging. The storage environment should be kept clean, cool, dry and ventilated.
For the safety test of cable insulation performance, a 1000V megger should be used. The test steps are as follows:
1. Power off the cable first and then discharge it. During the discharge process, each core wire is grounded, and the longer the cable, the longer the discharge time is, waiting for the spark and discharge sound.
2. Remove the double end of the cable from the equipment and the line. For example, when testing the A phase core to the ground, terminate the B and C cores and ground them, and finally connect with the “e” end of the megohmmeter. The wire is held by the insulator, and then held by one person, and the other person turns the handle 120 turns.
3. The wire end is in contact with the A-phase core and the reading is recorded after one minute. After the line is removed, the megger is stopped and the cable is finally discharged.
4. According to the above steps, measure the insulation effect of B to ground and C to ground. Remember that the insulation resistance of each core to ground should not be less than 10mΩ.