An earthed system has the supply neutral point connected to earth.
Shipboard main LV low voltage systems at 440v ac are normally insulated from earth ships hull similat systems ashore are normally earthed to the grounded.
HV high voltage systems >=1000v are usually earthed to the ships hull via a neutral earthing resistor NER or through a high impedance transformer to limit earth fault current
The priority requirement on board ship is to maintain continuity of the electrical supply to essential equipment in the event of a single earthed fault occuring.
A circuit consists essentially of two parts
1.conductor, the part which carries through the circuit
2.insulator, the part which keeps the current inside the conductor.
