Marine Electricity or Marine electrical power is a vital part of a ship’s operation. Without marine electricity, ships would not be able to run any of the machinery and cannot perform their core purpose of sailing from one place to another.
What is marine electricity?
The electricity which is produced, supplied and distributed onboard ship, port, drydock, shipyard for running or repair of the cargo and passenger ships is referred to as Marine electricity.
Marine electricity generation can be done onboard ships by diesel, shaft or steam-driven generators. The ships plying in the international waters generally have 3 phase D.C. supply with 440v insulated neutral system. Ships like RORO, passenger etc. having large electrical load requirements are installed with high voltage operating gensets in the range of 3KV to 11KV.
On ships, 60hz frequency is adopted as standard practice which helps hundreds of motors on a ship run at higher speed even if they are of smaller size. The supply which is at 440v is stepped down using a transformer to 220V or 110V for lights and low power signal equipment.
Parts of the Marine Electricity System
The electrical onboard ships can be divided into five specific systems:
- Generator system
- Main Switchboard System
- Emergency Switchboard System
- Distribution system
The generator system consists of an alternator and driver for the alternator which can be a diesel-driven or steam-driven engine.
Many ships are equipped with shaft generator where the rotation of the main engine of the ship is used to operate the alternator and generate additional electricity.
The Power generated by these marine generators is transported to the Main switchboard using Busbars. There are no electrical wire connections inside the main and emergency switchboards on ships for connecting Power supply from generators to these switchboards. All high voltage and high current systems are connected by bus bars.
Main Switchboard System
The main switchboard is considered as the distribution hub of the ship’s electrical system taking power from the power generator and distributing it to the power consumer spread all over the ship. It provides a power supply to all important ships machinery with 440V.
A part of the main switchboard is provided with a 220V supply via a stepdown transformer. It includes bridge equipment, navigation lights, radio communication equipment, etc. The power from the auxiliary switchboard is used to charge the battery which is used for emergency lights.
Emergency Switchboard System
An emergency generator is required to be operational at all times once the main generator fails. This emergency generator will start automatically and provide power to the emergency switchboard.
All the emergency equipment supply is connected to the emergency switchboard. The emergency switchboard is also divided into two sections – 440V and 220V, providing supply to appropriate machinery and equipment.
Distribution boxes: These boxes are enclosed and made up of metal to supply power to localized parts of the ship’s machinery.
Motor starter boxes: There are hundreds of motor operating several mechanical machinery onboard ship. Each group of motors is provided with a motor starter boxes containing their “On & OFF” switch along with safety devices. Local gauges for amperage and temperature are fitted on the starter panel.
Shore connection boxes: When the ship is in a port with emission control requirements or during the dry-docking process where the ship generator cannot run, shore power is taken for running ship machinery. Shore panel is provided which is usually located near accommodation entry or near the bunker station to easily accept shore supply cable.
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Source: Marine insight