1, Testing of insulation resistance
Insulation resistance is an important indicator reflecting the insulation characteristics of wire and cable products, closely related to electrical strength, dielectric loss, and the gradual deterioration of insulation materials under working conditions.
By measuring the insulation resistance, defects in the process can be discovered, such as dry insulation or damaged and damp sheaths; Insulation is contaminated and mixed with conductive impurities; Insulation cracking caused by various reasons. During the operation of wires and cables, insulation resistance and leakage current often need to be tested as the main basis for whether they can continue to operate safely.
2, Measurement of capacitance and loss factor
When AC voltage is applied to a cable, current flows through it. When the amplitude and frequency of the voltage are constant, the magnitude of the capacitive current is proportional to the capacitance (Cx) of the cable. For ultra-high voltage cables, the current of the capacitor may reach a value comparable to the rated current, which becomes an important factor limiting the cable capacity and transmission distance. Therefore, the capacitance of the cable is also one of the main electrical performance parameters of the cable.
Through the measurement of capacitance and loss factor, various insulation degradation phenomena such as insulation moisture, insulation layer and shielding layer detachment can be discovered. Therefore, capacitance and TAN measurements are carried out in both cable manufacturing and cable operation. For high-voltage cables, the measurement of Cx and TAN is carried out under working conditions of high frequency voltage, usually using a high-voltage Xilin bridge. In recent years, current ratio transformer bridges have also been used.
3, Partial discharge measurement
Electrical measurement method: There are many methods for measuring partial discharge, which can measure the discharge pulse based on the instantaneous charge exchange generated by the discharge;
Acoustic measurement method: The voltage can also be measured based on the ultrasonic waves generated during discharge;
Light measurement method: It can also measure the intensity of light based on the light generated by discharge;
