The voltage drop is calculated in accordance with the following equation:
,where:

• In, rated current [A],
• l, length of cable [m],
• σ, conductivity, for copper 58 [S*m / mm ² ],
• Un, rated voltage [V],
• s, cable cross-section [mm ² ],

Voltage drop on cables between generators and main switchboard is not to be more than 1%

Voltage drop is not to exceed:

• 10% for lighting and signalling devices,
• 10% for power consumers at short-time and intermittent service
• 7% for power and heating devices,
• 5% for navigation light circuit.

Permissible voltage drop is given in:

• 6.8.5 and 16.8.3, Rules for the Classification and Construction of Sea-going Ships - Part VIII, Electrical Installations and Control Systems,
• 6.3.8 and 13.8.13, Rules for the Classification and Construction of Small Sea-going Vessels - Part VII, Electrical Installations and Automation,
• 6.5.7 and 14.6.3.2, Rules for the Classification and Construction of Inland Waterways Vessels - Part VII, Electrical Equipment and Automation,
• 15.2.3.1, Rules for the Classification and Construction of Floating Docks - Part VI, Electrical Equipment,
• 8.2.3, Rules for the Classification and Construction of Sea-going Yachts - Part V, Electrical Equipment,
• 8.2.3, Rules for the Classification and Construction of Motor Boats - Part V, Electrical Equipment.