The galvanic isolator prevents electrolytic corrosion. It blocks low-voltage direct current from entering the boat through the shore power grounding wire. Such current can cause corrosion in the underwater metal parts of the boat, such as the hull, propeller, shaft, and so on.
Inside the galvanic isolator, there are two diodes connected in reverse parallel. When this type of connection is used, the diodes allow electric current to flow in both directions, but only above a certain voltage threshold. The direct current voltage that ensures the conductivity of the diodes is approximately 1.4 V.
The isolator is installed directly behind the boat's 230 V connection. The voltage coming from the galvanic isolator is higher than the potential difference between the metals. As a result, this voltage does not allow current to flow, and therefore the galvanic isolator prevents electrolytic current. However, if there is a (higher) fault voltage present in the alternating current circuit, the diodes will allow current to pass, and the residual current device will interrupt it.
