How does this surge protection work?
I can read and write Chinese.  So let me translate.
The schematic has 4 blocks on the top row, another at the bottom.
The labels are:
Top: Sensor, Voltage limiter, Surge processing circuit, Optocoupler
Bottom: Remote input, alarm circuit, core MCU, long distance transmission circuit.
I think it is the top left block's L01 inductor that picks up the surge and kick starts everything.