A Galvanic Isolator is a device designed to block destructive current flow between a vessel and the submersed metals of other vessels and structures.
There are a number of ways that corrosion of submersed metals can occur on a vessel. One is via the earth wire of a shore power connection. The vessel's shore power earth wire is connected to the same shore 'earth' that other adjacent vessels are connect to.
This creates a common connection between all vessels connected to that shore power system.
This common connection can create an electrical path for current to flow between connected vessels, allowing the submersed metal components of those vessels to react with each other.
The BACMAR galvanic isolator blocks that destructive current flow while maintaining the continuity of the vessel's safety 'Earth' wire.
New Zealand law does not allow this device to be installed by anyone other than a suitably trained and 'registered' electrician. Most 'marine' electricians in New Zealand are not qualified to work on shore power systems or to install or test this device.