The selection of qualified wire and cable products is related to people's safety in production and life. For ordinary consumers, it is necessary to understand the conventional monitoring knowledge of wire and cable in addition to how to select the qualified wire and cable products. In the quality detection of wire and cable, there are several important indicators.

Measurement of capacitance and loss factor:

When the cable is coupled with AC voltage, the current flows through it. When the amplitude and frequency of the voltage are constant, the capacitance current is proportional to the capacitance of the cable (Cx). For ultra high voltage cables, the current of this capacitor may reach the value that can be compared with the rated current, which is an important factor to limit the capacity and transmission distance of the cable. Therefore, the capacitance of the cable is also one of the main electrical parameters of the cable. In AC electric field, the dielectric loss in the cable is caused by leakage current and various polarization, which is represented by dielectric loss factor or loss angle tangent (TAN). It not only wastes electrical energy, but also causes heat of dielectric (insulator) and accelerates the aging of insulation, so TAN is one of the main parameters of cable. Through the measurement of capacitance and loss factor, all kinds of insulation deterioration, such as insulation dampness, insulating layer and shielding layer, can be found. Therefore, the measurement of capacitance and TAN can be carried out in both cable manufacturing and cable operation. The measurement of high voltage cable, Cx and TAN are under the working condition, that is, under the high pressure of the power frequency. The high voltage Xilin bridge is usually used. This year, the current ratio of the transformer bridge is also used.