Emergency switchboard

According to the degree of importance, power consumers on board are divided into 3 groups:

- critically essential consumers, a power interruption of which can lead to an accident of the ship and death of people.

These include radio and navigation equipment, in accordance with the Rules for the Conventional Equipment of Marine Ships: steering gear, fire pump, emergency lighting, etc. On ships, the consumers of this group are powered almost uninterruptedly from the mains, and when it is de-energized, from an Emergency Power Plant;

Figure 48. Critically essential power consumers section (powered from ESB)

- essential consumers, that ensure the operation of ship’s power plant, ship control and cargo safety. This group includes such ship's power consumers - pumps, fans, compressors, winches and windlasses, cargo devices, on-board communications and signalling, etc. These consumers receive power in all operating modes of the Main Ship Electrical Plant (SEP);

Figure 49. Essential power consumers section (powered from MSB)

 

- unessential consumers that allow power interruption in emergency situations or when SPP is overloaded – cargo hold ventilation, galley equipment, air conditioning system etc.

To ensure the continuity of power supply to important consumers, the following methods are used:

1. installation of an Emergency Power Plant on the ship, from the busbar of which critically essential consumers receiving power;

2. redundancy of consumers, one of which, being in operation, is considered the main one, and the other one is the reserve one (stand-by). Such consumers include, for example, steering electric drives installed in Steering Gear room in double quantity;

3. power supply of consumers through separate feeders, one of which is connected to Main Switchboard, and the other to Secondary Switchboard or ESB. In this case, the feeders receive power from different sections of the Main Switchboard spaced at a sufficient distance from each other. For example, steering drives are powered by two feeders, one of which is connected to the Main Switchboard, and the second - to the Emergency Switchboard. These feeders are laid along different sides of the vessel;

4. automatic switching of the power supply of a single power consumer from one feeder to another, etc.

Composition of power receivers of Emergency Power Plants

The ship’s Emergency Power Plant is designed to supply power to critically essential consumers in the event of an emergency condition of the Ship's Main Power Plant (ship blackout).

Figure 50. Emergency Switchboard

 

In the event of a failure of the Main Power Plant, the following receivers should be powered from the ESB buses:

a) from the ESB busbar directly:

1. fire pump;

2. electrical equipment that ensures the operation of the fire system;

3. emergency lighting;

4. means of internal communication and notification necessary in emergency conditions;

5. alarm systems, fire detection system and control devices, alarms indication panel of fire doors;

6. devices for closing watertight doors, signalling their position and preventing their closing;

b) from the ESB busbar, throw the ship control panel located in the wheelhouse:

1. signal and distinguishing lights, "cannot steer" signal lights and other lights required by the current International Regulations for Preventing Collisions between Vessels;

2. means of intercom and notification, as well as emergency signalling;

3. appropriate radio and navigation equipment;

4. fire detection and alarm systems.

5. daylight signalling lamps, sound signalling means (whistles, gongs, etc.) and other types of signalling required in emergency conditions.

In the event of failure of both power plants - the main and emergency, the third source of electrical should automatically turn ON - a 12 (24) V battery, from which a limited number of low-power consumers are supplied:

1. emergency lighting and necessary signal and distinguishing lights;

2. all means of internal communication and notification necessary in emergency conditions;

3. fire detection and alarm system;

4. daylight signaling lamps (ALDIS lamp), sound signaling means (whistles, gongs, etc.).

The receivers listed in 2, 3 and 4 may not be powered by a common (single) battery if they have their own batteries to provide power for the required time.

Figure 51. Emergency batteries

Placement of Emergency Power Plant

Emergency PP consists of a power source and a switchboard located in a special room (Emergency Power Plant room or Emergency Diesel-Generator room).

Emergency Power Plant is installed on all self-propelled ships, except for those whose main sources of electricity are batteries, provided that at least one of them meets the requirements for an emergency source in terms of capacity and location.

The Emergency PP compartment should be located above the bulkhead deck, one deck above the uninterrupted weather deck, outside the engine room funnel and aft of the collision bulkhead. The exit from this room should lead directly to the open deck.

On many ships, the Emergency Power Plant is installed in a separate room on the boat deck. However, on some types of ships (big fishing boats), an Emergency Power Plant is installed in a service room on the main deck.

Figure 52. Ship's Emergency Diesel-Generator room

 

Features of power supply of cargo and passenger ships

The power of the ship's Emergency Power Plant must be sufficient to simultaneously supply all its power consumers.

The source of electricity for an Emergency PP can be a DG or batteries. Batteries must be connected to the emergency grid when the voltage in the mains is turned OFF.

On passenger ships, the Emergency Power Plant must remain operational for 36 hours, on cargo ships of unlimited and limited navigation areas, with a gross tonnage of 300 reg. t and more – 18 h.

Figure 53. Emergency Diesel-Generator fuel tank

 

On cargo ships, the Emergency Power Plant provides electrical power to the emergency lighting networks, signal lights, emergency alarm systems, intercom and signalling systems, necessary in case of an accident, radio and navigation equipment, fire detection systems, sound signalling means, a fire pump and a steering gear.

Start-up of the Emergency Diesel-Generator (EDG) can be manual or automatic; in the 2nd case, the EDG must start up and power-up the rated load in a time not exceeding 45 s.

If no automatic start is provided or the load can’t be taken over for more than 45 s, a short-term emergency source of power shall be provided.

Such a source is a batterie, which, without additional charge, provide power for emergency lighting networks, signal lights, emergency signalling and intercom networks necessary in case of an accident, fire detection systems in the ship’s compartments, sound signalling devices and daytime signalling lamps (ALDIS lamp) for 30 minutes without additional charge.

 

Schematic diagram of ESB

In the event of an emergency condition of the Main PP, the Emergency Power Plant becomes an autonomous and the only source of electricity on the ship.

In the normal mode of operation of the ship, the EDG does not work, but some of the switching devices of the Emergency PP Switchboard are used to supply power from the Main Switchboard, when discharged, batteries are connected to charge, and the insulation resistance is controlled.

In this mode, Emergency PP consumers are powered from the Main Switchboard, and in emergency mode they switch to power supply from the EDG.

In non-emergency mode, voltage is supplied to the ESB buses from the Main Switchboard by means of TIE Breaker.

Figure 54. Single-Line diagram of Emergency Switchboard

 

Structurally presented scheme of the switchboard is mounted in a 3-panel board. Its panels are equipped with contactor control buttons, control and measuring instruments with switches, start test buttons for the EDG, an insulation resistance control device, buttons for turning on the Generator ACB.

The load of the Emergency PP is controlled by a common ammeter, the most powerful power consumers have a separate ammeter with a switches.

Charging devices for starter batteries of the EDG are installed in the switchboard or separately in the Emergency PP room.

The requirements of the Register Rules (Lloyd, ABS, Veritas etc.) for voltage stabilization of the EDG are less stringent than for auxiliary or shaft Generators (an error of ± 3.5% of the rated voltage is allowed), therefore, the Emergency PP is made according to the simplest scheme (usually without a voltage corrector).

Automatic start system of the EDG when the vessel is de-energized

The start program can be implemented using electromechanical contact devices or an electronic circuit.

In the first case, when Main PP fails, the Electric Drive (ED) of the program device is turned ON, which rotates the cam roller through the slowdown gearbox. Which, in a certain sequence, at predetermined time intervals, switches contacts, which, in turn, control relays and other devices to start the EDG and take-over the load.

In the second case, with the help of an electronic circuit, a program is implemented to control the contact part of the start-up circuit of the EDG and take-over the load.