Cable testing wire and cable quality testing several important objectives Cable testing insulation resistance test: Insulation resistance is an important target reflecting the insulation characteristics of wire and cable products, which is related to the product's electrical strength, dielectric loss, and insulation materials under working conditions. Gradual deterioration, etc. are closely related. For communication cables, if the insulation resistance between wires is too low, it will also increase loop attenuation, crosstalk between loops, and long-distance power supply leakage on the conductive core. Therefore, the insulation resistance is required to be higher than the specified value. Determination of insulation resistance can find defects in the process, such as the insulation is dry and easy to crack or the sheath is damaged by moisture; the insulation is polluted and mixed with conductive impurities; the insulation layer is cracked due to various reasons, etc.
In the operation of wires and cables, it is often necessary to detect insulation resistance and leakage current as the primary basis for continuous and safe operation. At present, the measurement of insulation resistance of wire and cable, in addition to using ohmmeter (shake meter), commonly used galvanometer comparison method, high resistance meter method (voltage——current method). Measurement of Capacitance and Dissipation Factor: When the AC voltage is applied to the cable, current flows. When the amplitude and frequency of the voltage are constant, the magnitude of the capacitor current is proportional to the cable's capacitance (Cx).
For ultra-high voltage cables, the current of this capacitor reaches a value that can be relatively stable with the rated current, which becomes an important factor constraining the cable capacity and transmission interval. Therefore, the capacitance of the cable is also one of the primary electrical performance parameters of the cable. In the communication electric field, the insulator in the cable will constitute dielectric loss due to leakage current and various polarizations, which is indicated by the dielectric loss factor or loss tangent (TAN ), which not only wastes electric energy, but also makes the dielectric (insulator) loss. ) generates heat and accelerates insulation aging, so TAN is also one of the primary parameters of the cable.
Through the measurement of capacitance and loss factor, various insulation deterioration phenomena such as insulation damping, insulation layer and shielding layer falling, etc. can be found. Therefore, capacitance and TAN measurement are carried out no matter in cable production or cable operation. For high-voltage cables, the measurement of Cx and TAN is carried out under its operating conditions, that is, power frequency and high voltage. Generally, high-voltage Xilin bridges are used, and current ratio transformer bridges are also used. Partial discharge measurement: There is basically no partial discharge on the oil-filled cable; even if the oil-paper cable has partial discharge, it is generally very weak, so these cables can detect partial discharge in the factory experiment.
Regarding extruded cables, not only is there a high possibility of partial discharge, but also the damage to plastics and rubbers caused by partial discharge is relatively serious. For plastic cables, partial discharge measurement is required in the factory test. Several important targets of wire and cable quality inspection cable inspection Shenzhen Noyafa Electronic Technology Co., Ltd.
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