How should surge protection be designed in a graded manner for power line carrier PLCs?

The surge protection hierarchy design for power line carrier PLCs needs to determine the protection level based on the application scenario. Level 1 protection (inlet) uses a 2R600L-8×6 gas discharge tube with a current carrying capacity of 20kA; Level 2 protection (front-panel) uses a 14D511K varistor with a current carrying capacity of 6.5kA; Level 3 protection (panel level) uses a TVS diode SMCJ24CA with a current carrying capacity of 100A. Each level is coordinated with a decoupling inductor (10μH) or resistor (10Ω) to ensure energy is discharged step-by-step. The design conforms to the IEC61643-11 standard, with a test waveform of 8/20μs. In actual testing, the system should pass a combined waveform test (6kV/3kA). This hierarchical design ensures equipment safety under lightning strikes or operational overvoltages.