Water ingressing into the oil chamber of submersible pumps emulsifies the water and rapidly increases its conductivity.
The relay picks up if the resistance between the pump housing and the oil chamber drops to approx. 30 kΩ.
Direct current flows in the electrode circuit to exclude the possibility of switching errors resulting from cross-capacitances. An LED indicates the control state of the relay. The module is designed to be mounted onto DIN/EN top-hat mounting rails.

At a glance:

Two potential-free CO contacts
Compact design
Easy to install