How to suppress lightning-induced overvoltage in intelligent low-voltage monitoring units?

Lightning-induced overvoltage suppression employs multi-stage surge protection.

Stage 1: An 8/20μs waveform surge protector (SPD) with a current carrying capacity of 10kA is installed at the input terminal.

Stage 2: A 2R090L-5.5×6 gas discharge tube (90V/3kA) is used at the equipment inlet.

Stage 3: A 7D390K varistor (390V/2kA) is used at the board level.

Stage 4: An SMBJ18CA TVS diode is used at the chip level. Inter-stage decoupling is achieved through a 2mH inductor or a 10Ω resistor.

Grounding system: Grounding resistance is less than 0.2Ω. This suppression allows the device to withstand a 5kA lightning strike with an 8/20μs waveform.