Galvanic isolator VDI-32

The galvanic isolator prevents electrolytic corrosion. It blocks low-voltage direct currents that enter your boat via the shore power ground cable. These currents can cause corrosion on the metal parts of the boat under water, such as the hull, propeller, shaft, etc.
The galvanic isolator consists internally of two diodes that are connected in an anti-parallel manner. This connection method allows the diodes to allow current to flow in both directions, but only when a certain voltage threshold is exceeded. The voltage at which the diodes conduct is 1.4 Vdc.

The isolator is installed directly behind the 230 V connection of your boat. The forward voltage of the galvanic isolator is higher than the potential difference between metals. As a result, the voltage does not allow conduction and the galvanic isolator prevents any electrolytic current. However, if a (higher) fault current occurs in the AC circuit, the diodes let the current through and the residual current device interrupts the circuit.