Wire and cable quality test three important indicators

author: Zhejiang Linquick Technology Co., Ltd.

2023-08-29

As the infrastructure of power, communication, and other related industries, the quality of wire and cable directly affects the reliability, security, and stability of the entire system. In order to ensure the quality of wire and cable, it is essential to carry out quality testing. The main purpose of quality inspection is to find potential defects, such as short circuits, aging, corrosion, etc., and repair or replace them in a timely manner. In the quality inspection of wire and cable, there are three important indicators that need special attention: conductor resistance, insulation layer thickness, and insulation material performance.

Here is an introduction to the three important indicators of wire and cable quality detection.

First, insulation resistance test

Insulation resistance is an important indicator to reflect the insulation characteristics of wire and cable products, which is closely related to electric strength, dielectric loss, and gradual deterioration of insulating materials under working conditions.

By measuring insulation resistance, defects in the process can be found, such as dry insulation or sheath damage and moisture; Insulation is contaminated and mixed with conductive impurities; Insulation cracking is caused by various reasons. In the operation of wire and cable, it is often necessary to detect insulation resistance and leakage current, as the main basis for whether it can continue to operate safely.

Second. Measurement of capacitance and loss factor

A current flows through a cable when AC voltage is applied. When the amplitude and frequency of the voltage are constant, the size of the capacitor 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 cable capacitance is also one of the main electrical performance parameters of the cable.
Through the measurement of capacitance and loss factor, various insulation deterioration phenomena such as insulation moisture, insulation layer, and shield layer shedding can be found, so capacitance and TAN are measured in both cable manufacturing and cable operation. For high-voltage cables, the measurement of Cx and TAN is carried out under the operating conditions of power frequency high voltage, usually using high-voltage Schilling Bridges, and in recent years, current ratio transformer Bridges have also begun to be used.

Third, partial discharge measurement

Electrical measurement method: There are many methods for measuring partial discharge, which can measure the discharge pulse according to the instantaneous charge exchange generated by discharge;

Acoustic measurement method: It can also measure the voltage according to the ultrasonic wave generated during discharge;

Light measurement method: The intensity of light can also be measured according to the light generated by the discharge;

For cables are basically used electrical measurement method.

Although cable has brought great convenience to our lives, at the same time there are many uncontrollable factors, the quality of the power cable directly affects the safety of the operation of the line, once the line can not operate safely and stably, it fails caused by life and economic losses are unpredictable, so we should fundamentally prevent the occurrence of cable failures, minimize cable accidents, Start from the details, and strive to achieve the goal of safe and stable power supply.