Most RCD's have three pins: a live wire passes through a high resistance VSE which stops it from carrying any stray current, and then on to a grounding pin which connects to the earth's potential.
#rcds #residualcurrentdevice
https://www.xvsy.com.au/solid-state-vs-mov-rcds/
![image](https://moonsignals.com/upload/photos/2024/01/Ob7bCN6vt9EnMU9VQThx_04_11c779e04c6511a8f855779272ddb349_image.jpg)