Shore power supply

А shore supply is required so that the ship's generators and their prime movers can be shut down for major overhaul during а dry docking period.

There must be а suitable connection box conveniently located to accept the shore supply cable. The connection box is often located at the entrance to the accommodation or in the emergency generator room. The connection box must have suitable terminals to accept the shore supply cable, including an earthing terminal to earth the ship's hull to the shore earth.

The connection box must have а circuit breaker or an isolator switch and fuses to protect the cable linking the connection box to the main switchboard, with а data plate giving details of the ship's electrical system (voltage and frequency) and showing the method for connecting the shore supply cable.

А voltmeter and а phase-sequence indicator (PSI) are fitted to indicate shore supply voltage and correct supply phase sequence. А phase-sequence indicator may incorporate either two lamps for “right” (R-S-T) and “wrong” (R-T-S) phase-sequence monitoring or а rotary pointer driven by an integrated small three-phase motor.

At the main switchboard, an indicator is provided (usually а lamp) to indicate that the shore supply is available for connection to the busbars via а connecting switch or circuit breaker. In general, it is impossible to parallel the shore supply with the ship's generators. The ship's generators must, therefore, be disconnected before the shore supply can be connected to the main switchboard.

Figure 40. Shore Connection

Figure 40 shows а typical shore connection arrangement.

Normally, the shore switch on the main switchboard is electrically interlocked with the generator's circuit breakers, so that it cannot be closed until the generators are disconnected from the ship's mains (as this will cause а brief mains blackout before shore power is applied).

On figure shows а typical shore connection arrangement, but some variations occur. The shore supply may have а different frequency and/or voltage to that of the ship's system:

- a higher frequency will cause motors to run faster, be overloaded and overheat

- а higher voltage will generally cause equipment to take excess current and overheat. it will also cause motors to accelerate more rapidly, and this may overstress the driven loads

- а lower voltage is generally not so serious but may cause motors to run slower and overheat, or to stall.

Alternative Maritime Power Supply (АМР).

The risks of pollution and sustained environmental damage in ports all over the world are becoming an increasing issue. Over the last 15 years, increasing attention has been focused on reducing the pollution from the auxiliary diesel engines of ships that frequent, in ever increasing numbers, the ports and terminals around the world. These ships keep their auxiliary engines running when moored in port to ensure а continued power supply for essential services.

The European Parliament has adopted а directive, 2005/33ЕС, which requires consideration to be given to the measures that should be taken to reduce the contribution the combustion of marine fuels other than marine gas oil makes to acidification. Amongst other measures, it recommends shore connection capabilities in EU ports.

The US State of California also adopted а resolution to take preventive measures, called “Airborne toxic control measure for auxiliary diesel engines on ocean-going vessels at berth in а California Port” (93118.3, Title 17, Chapter 1, subchapter 7.5, California Code of Regulations). This section calls for а reduction in emissions by limiting the time during which auxiliary diesel engines are operated on regulated vessels while docked at berth in а California port.

The IMO's Marine Environment Protection Committee (МЕРС) agreed to а number of new regulations that were inserted into Annex VI of MARPOL to deal with the greenhouse gases emitted from ships. The measures will affect all ships and require the issue of а new certificate called the International Energy Efficiency Certificate (ІЕЕС). ln addition, all new ships with а keel laying date on or after 1st July 2013 will also be required to meet the Energy Efficiency Design Index (EEDI) and the Ship Energy Efficiency Management Plan (SEEMP).

ln accordance with these new regulations, “In some ports shore power may be available for some ships, but this is generally aimed at improving air quality in the port area. If the shore-based power source is carbon efficient, there may be а net efficiency benefit. Ships may consider using onshore power if available.”

This means that each vessel brought into service in future should be fitted with а facility that allow brief parallel working of the ship's power plant with а shore power supply substation for taking over the power from shore and back while moored at the port.

Many port and ship operators in Denmark, Finland, Norway, Sweden, the UK, the USA, etc. use shore-based electricity while moored in port.

А few alternatives to this system are available. The first is to mount the cable management system on the ship or shore. The connection to shore is made via special HV cables to an integrated technical pit fitted into the quay. This application occupies а minimum of space and consists of the following components: electrical connectors (up to 12 kV), flexible cables, а slip ring assembly, an optical fiber accumulator, а motor reducer, а cable drum and an electrical control panel.

Figure 41. Shore-based AMP

Figure 42. Ships AMP

 

Another alternative is to have а similar system fitted inside а standard-size container, which can be placed on the ship. As the whole system is inside а container, and therefore completely modular, it can remain in а fixed position on board for longer periods or, if necessary, can be moved on board another ship.

Figure 43. Standard-size container AMP

 

Such systems are becoming part of many ports' stationary and movable power network (barge mounted or vehicle-based).