Method and System for Online Monitoring of Dielectric Loss Factor in Cross-Linked Cables

With the acceleration of urbanization, cables are increasingly replacing overhead conductors as primary transmission lines. However, long-term operation exposes cables to combined electric and thermal fields, leading to insulation degradation through mechanisms such as polymer breakdown, electrical treeing, and water treeing. This results in an elevated dielectric loss factor, a critical performance indicator. While existing online monitoring methods, such as partial discharge detection, gas analysis, and temperature measurement, are well-established, research on dielectric loss factor monitoring remains limited, particularly for cross-linked cable systems. This paper proposes an online dielectric loss factor monitoring method for cross-linked cable insulation, leveraging real-world engineering data. Voltage and grounding current signals are acquired via transformers and synchronized using GPS or BeiDou time systems to ensure phase consistency. The signals are processed with a Butterworth filter, and the dielectric loss factor is calculated by a microprocessor. The calculated value is compared against standards to assess insulation health. Field tests validate the method's accuracy in monitoring dielectric loss factor, providing a scientific foundation for cable operation and maintenance.