Paper-Insulated Wire Testing Process: A Systematic Approach to Ensure Insulation Reliability

As a key winding material for high-voltage power equipment and large motors, the insulation performance of paper-insulated wire directly affects the operational safety and lifespan of the equipment.A scientific testing process is not only a quality control step before product delivery but also a crucial means of post-commissioning condition assessment and fault prevention. Considering the structural characteristics and actual application environment of paper-insulated wire, the testing process typically covers visual inspection, dimensional measurement, electrical performance testing, thermal performance evaluation, and oil-paper composite state analysis, forming a comprehensive verification system from material to finished product, from static to dynamic aspects.

Testing begins with visual and dimensional verification. It is necessary to check whether the paper layer coverage is uniform and continuous, without wrinkles, damage, bubbles, or local delamination; the conductor surface should be smooth, free of oxidation and scratches. Precision measuring instruments are used to measure the conductor diameter, paper layer thickness, and winding pitch to confirm conformity with design specifications, providing basic data for subsequent performance testing.

Electrical performance testing is the core step, typically including insulation resistance measurement, dielectric strength testing, and partial discharge detection. Insulation resistance testing determines the insulation integrity between the paper layer and the conductor, as well as between layers. Dielectric strength testing verifies the paper-insulated wire's withstand capability under short-time overvoltage by gradually increasing the voltage to a specified value. Partial discharge detection can detect weak points in the insulation under conditions close to the operating field strength, preventing potential breakdown risks. For oil-impregnated paper-insulated wires, withstand voltage and dielectric loss tests of the oil-paper composite insulation are also required to assess impregnation quality and interface stability.

Thermal performance evaluation mainly includes heat aging and thermal stability testing. Samples are placed in a specified high-temperature environment for a certain period, and then their electrical and mechanical properties are retested to determine the performance retention rate of the paper layer under long-term thermal effects. This item is particularly important for equipment operating in high-temperature conditions or applications in tropical environments.

For oil-impregnated paper-insulated wires, oil-related testing is required, including dissolved gas analysis (DGA), water content, and acid value determination, to determine the aging trend and moisture absorption degree of the oil-paper system during operation or storage. Thermal imaging or local temperature rise monitoring may be used as needed to locate abnormal hot spots.

The testing process also includes recording and judgment steps. All test data must be compiled into a complete report, and pass/fail determinations must be made based on standard limits. Non-conformities must be traced back to the production or storage stages to drive continuous improvement.

Overall, the paper-insulated wire testing process, through a systematic and hierarchical testing method, achieves comprehensive control over the material's condition and reliability, providing a scientific basis for the safe operation and lifespan management of high-voltage electrical equipment.