In order to ensure the safe operation of the power system and the safety of people's lives and property, the state has formulated a number of qualification standards for the production process of wire and cable. Wire and cable before leaving the factory must be carefully carried out in accordance with the standard test items. Today Pai De cable to talk about cable detection ~
Wire and cable testing items are mainly divided into: appearance and structure testing, electrical performance testing and mechanical performance testing.
structural dimension inspection
Appearance and structure inspection is the first inspection elements in the quality control of wire and cable, inspection elements can be divided into: appearance inspection, size inspection, structure inspection and mark inspection.
Visual examination
The surface of insulation and sheath must be smooth and round, uniform luster, no eccentricity, no mechanical damage, smooth, no debris, bubbles, pores and obvious particles visible to normal vision;
There should be no uneven thickness and slub shape, no adhesion between insulation and conductor core, insulation and insulation, insulation and sheath. The spark breakdown repair point must be smooth and flat.
Dimensional inspection
Sampling and result evaluation: Three insulation samples were taken from each insulated wire core, and the average value of 18 values was determined. The result was retained to 1 place after the decimal point. Two decimal places. The insulation layer thickness of various wires and cables should not be less than the relevant provisions.
Character detection
The national standard requires that the mark on the wire and cable must have the characteristics of wear-resistant and continuous, and must maintain a high degree of clarity. The detection method is to wipe the absorbent cotton ball dipped in alcohol back and forth several times at the mark on the wire and cable. If it is still clear after wiping, it means that the brand is qualified.
Continuity refers to the distance between the end of one sign and the starting point of the next sign, the sheath ≤550mm, the insulation ≤275mm, the distance between the two adjacent sets of digital signs must be ≤50mm.
Dc resistance detection
Dc resistance is used to test the electrical conductivity of wires and cables. The material and cross-sectional area of the wire and cable will also directly affect the size of the DC resistance, so the DC resistance detection method is used to detect the quality of the material.
Dc resistance detection is tested according to the resistance law, R=pL/S, where p is the resistivity, L is the length of the conductor, and S is the cross-sectional area of the conductor.
The national standard stipulates that the resistance value of the conductor reaches the maximum value at 20°C, so the DC resistance data of the wire and cable must first be converted into DC resistance data kilometers at 20°C, and then compared with the national standard value, if less than the standard value, it is qualified.
Insulation resistance test
Insulation resistance test refers to the resistance value of the insulating material between two conductors under specified conditions.
Insulation resistance is an important property of wire and cable products. The insulation resistance reflects the insulating ability of the product under normal operating conditions. It is related to the ability of the product to withstand electrical breakdown or thermal breakdown, the dielectric loss in the insulation and the gradual aging of the insulation material under working conditions have a very close interdependence, so most wire and cable products must measure the insulation resistance performance.
The insulation resistance of the product mainly depends on the insulation material selected, but the process level has a great impact on the insulation resistance. Therefore, the purpose of insulation resistance testing of products normally produced in factories is mainly as a way to monitor the quality of materials and processes.
By testing the insulation resistance, you can temporarily assess whether the cable insulation is affected by moisture, aging, dirt and local defects, and check the nature of the defects found in the voltage test. For rubber and plastic insulated power cables, the insulation resistance of the outer sheath and the inner sheath of the cable can be tested to assess whether the outer sheath and the inner sheath have water seepage.
