Does this PRCD have any differential current transformer inside?
If you pop the cover off I would expect to see a typical ASIC and a ZCT transformer. It has the usual test and reset switches and fault indicator lamp.
According to the description of operation in this advertisement, there is a sense transformer inside.

Which Google translates to (emphasis added):

When a leakage or electric shock occurs, the transformer in the leakage protector will immediately generate an induced voltage, and the internal power will be automatically cut off to prevent electric shock accidents caused by leakage. After the leakage or danger is eliminated, press the reset button to restore normal use

Based on photos of other products from this company, the (~25mm diameter) ZCT is at the output terminal block end and is free-floating inside the polycarbonate housing. Load appears to be a 1K 1% resistor.