Grid connected Energy Storage System (ESS) The DC ground cabling should be able to carry a fault current at least equal to the DC fuse rating. Connect the chassis of the inverter/charger to the ground busbar The AC-out ground may be taken from the central busbar or from the AC-out terminal.
7. Galvanic corrosion Galvanic corrosion is a DC current. It is caused by the natural voltage difference between metals. A galvanic current can only exist when there is a closed electric circuit. A conductor belonging to another electric circuit can be part of the galvanic corrosion circuit. If a boat with a metal hull is near the shore a natural voltage difference of 0.1 – 1 Vdc exists between the hull and the water. This potential difference leads no nothing as long there is no completion of the electric circuit. As soon as shore power is connected to the boat, the shore earth is automatically connected to the boats hull and the
electric circuit is complete. Now the following circuit is made: hull – water – shore – earth spike – earth wire – hull. A current will flow through this circuit, called galvanic current. The galvanic current partly runs through the AC circuit but is not related to that circuit. Current will continue to flow until the potential difference is eliminated. The height of the current depends on the resistance of the electric circuit. The resistance is determined by factors like the length of the shore power cable and local earth spreading resistance.
Chemically speaking, the “weakest” metal in the galvanic circuit will be the quickest to submit its molecules to the keep the current going. If the hull of the ship is part of the galvanic circuit and the hull contains the weakest metal, the hull will start to corrode over time. This can develop into a nasty situation, if leaved unchecked; it can become quite expensive and unsafe. There are known cases of ships having sunk due to galvanic corrosion. Aluminium hulls are notoriously susceptible to this kind of corrosion. Galvanic corrosion can also exist between the different metals attached to a boat, like screw, motor, hull and so on. All these parts are connected to earth and therefore additional small currents will run between these parts. This is the reason sacrificial anodes are mounted. A sacrificial anode is a piece of metal that is weaker than the metal around it. Therefore, they are sacrificed in order to protect the other metals. They can only prevent corrosion by postponing it. What type of sacrificial anode to use, depends on the type of metal it protects and what type of water the boat is in. It is recommended to regularly check these anodes.
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