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PMS - Power Management System |
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Switchboard, generator and engine control
The HMA Power Management System (PMS) is a computer based system for switchboard, generator and diesel/gas engine control.
The PMS performs all normal functions necessary to handle the power generation for the vessel: controlling the diesel generators, synchronizer, governors and MSB breakers.
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The load sharing mode is isochronous, where the gouvernor is handling the load and frequency control. The operator interface is performed by one/two operator stations (GMR100),
where all essential information in the system is presented. By a number of VDU pictures, the operator will get the status information, and be able to control parameters and functions in
order to provide the necessary number of generators connected to the MSB. The major PMS functions are:
- Load dependent start/stop
- Standby start, pre warning
- Standby start, shutdown
- Alarm handling/status indication
- Mode handling (keeps a mode-defined number of DGs connected)
- Partial/total blackout handling
- Volt/frequency alarm handling
- Reconnection of breakers after blackout
- Load control of propulsion drives
DGCU - Diesel Generator Control Unit
The PMS and generator control is located in two identical DGCU (AC800M), which is equipped with digital and analogue inputs and outputs. The DGCU will receive commands from the OS.
Operator Stations
The OS is running a display information system under Windows XP, and is connected to the PMS via a ethernet protocol. It receives information from the AC800M units and makes this
information available for the operator by means of several displays.
Connected generators and start sequence
At system configuration, the number of connected generators and the desired engine start order sequence are defined. The system will automatically arrange the generators, breakers and other
components in order to do the desired configuration. If any generator should fail, an alarm is generated and the actual generator is given up, and the next generator in the start order selection
is used instead.
The actual number of connected generators is controlled from the total power consumption and actual mode selected, preferably calculating a minimum number of generators required in order to
keep the load at each DG within the limits set in the system.
Load mode
Different load modes determines the number of generators to be connected, regarding or regardless of the consumed power. The actual modes will be adapted for each vessel, and may be a combination
of loads, number of connected generators, or other units to be started.
When full diesel engine capacity is needed, the load control function controls the power to the drives and keeps the RPM to the maximum power level for the generators.
PMS Local operation
Diesel generators may be operated locally at engine panel/switchboard (disabling the PMS) or remote/auto from the PMS.
PMS Auto Functions
The PMS auto functions are:
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- Auto start/stop - handles the start/stop of the engine in situations when this is required by the power demand, and contains different programs for load dependent start/stop of generators
- Automatic synchronizing - when the system is handled by an external synchronizer located in the MSB, activated with a relay contact from the PMS
- Shut down function - when an engine shut down is detected, a signal is sent to the PMS which will immediately disconnect the breaker and start the next generator in the sequence
- Pre-warning alarm - a function which automatically starts the next available generator if any engine conditions which will lead to a shut down of the engine is
getting critical near the shut down limit
- Alarm handling - each generator object has a number of calculated alarms (system failure, start failure, sync failure, breaker tripped, disconnect failure, stop failure, run failure,
power failure, breaker signal alarm, frequency/volt failure), which will be rised and needs to be reset by the operator
- Blackout - handles both partial and total blackout, and reconnects important breakers after blackout
- Load reduction - each thruster drive will get an available power signal from the PMS, and the system will prevent the generators from overload, and reduce the risk for a total blackout
in case of an unpredictable generator trip, in a sudden critical manoeuvring situation.
Failure Modes
The design philosophy is that no failure of any system component shall lead to any changes in the system. In case of any system fail, all contacts will remain in the same position, or open:
- Failure at the Operator Station - the current commands will remain in the AC800M, and when the OS is restarted it will resume operation at the position it failed without
interruption of the compressors
- Failure at control units AC800M (DGCU) - with two separate systems, any failure of one of the two generator control units will only affect the generators connected to the faulty unit,
and the opposite system will work normal
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