Online Insulation Monitoring Method for Power Cables in Wind Farms Considering Grid-Side Impedance Variations

The insulation ageing of power cables in wind farms is critical to safe operation. However, existing online monitoring methods for cables face challenges due to grid-side impedance variations. In this paper, the problem where the grid operating condition affects the cable insulation monitoring is solved. First, power cables and the grid are modeled as equivalent circuits of cascaded L-sections. Then, series resonant frequencies of the impedance are derived as Fibonacci polynomials. The effects of cable insulation aging and grid-side impedance variations are decoupled by analyzing the root ratio curve of polynomials. Next, experimental validation on the hardware-in-the-loop simulation platform shows that the equivalent insulation capacitance of cables can be accurately estimated with less than 0.83 % error under different grid-side impedances. The results confirm that the proposed method provides a reliable solution for online insulation monitoring of cables even when the grid is operated variably.