The Impact Of Rapid Decline In The Insulation Performance Of Ac Reactors On Equipment Reliability And Electrical Characteristics

In the field of industrial power systems and power electronic equipment, the degradation of the insulation system of ac output reactor is often a potential source of failure. Once insulation performance rapidly declines, system electrical parameters, thermal behavior, and long-term stability change significantly, posing challenges to operation and maintenance.

Impact of Insulation Degradation on Electrical Characteristics

Under strong electric fields and temperature stress, the electrical properties of insulating materials change during the degradation process. During the rapid degradation phase of the insulation system, the dielectric loss angle and resistive current characteristics change, meaning that internal leakage current may increase, and the reactor's reactance and resonant characteristics will also be affected. Such changes are common in the evolution of dielectric constant and loss factor after chemical denaturation and physical structural damage of dielectric materials.

An increase in the proportion of resistive current within the insulation layer causes the actual voltage distribution to deviate from the original design value, thus altering the reactor's impedance characteristics. This not only affects the system's power transmission efficiency but may also introduce additional stress under high-frequency or transient conditions, thereby amplifying local electrothermal effects.

Insulation Degradation Process and Stages

Under actual operating conditions, the degradation of insulating materials typically progresses through multiple stages, which can be summarized as follows:

Initial Changes

Initial degradation is mainly manifested as the accumulation of microscopic material structure relaxation and chemical bond breakage. At this stage, electrical parameters such as dielectric loss angle and local leakage current fluctuate slightly, but there is no obvious risk of breakdown.

Mid-Stage Development

With the accumulation of heat and stress, and the intensification of environmental erosion, the insulation resistance decreases significantly, forming micro-discharge channels within the insulating medium. Non-uniform electric fields intensify local stress concentration, potentially leading to frequent partial discharge phenomena.

Late-Stage Degradation

When the insulation structure becomes unstable to a certain extent, the breakdown voltage along the surface and in space decreases significantly. Electrical equipment is more prone to comprehensive insulation failure under long-term power frequency or transient impacts. This stage is a high-risk zone, posing a serious threat to operational continuity.

Operation, Maintenance and Condition Assessment Reference

Monitoring of ac reactor for inverter insulation performance should include a comprehensive assessment of changes in electrical parameters, thermal behavior trends, and material aging indicators. By monitoring data on insulation resistance, dielectric loss, and partial discharge, different stages of the degradation process can be identified, allowing for adjustments to maintenance strategies.

Especially under high-voltage and high-frequency operating conditions, rapid insulation degradation is often accompanied by the interplay of thermal stress and environmental factors, forming an electrothermal coupled degradation path, which poses a substantial constraint on equipment stability. Therefore, periodic insulation condition analysis and life assessment help in the timely development of maintenance plans and improve the overall reliable operation of the power system.