5.1.3 Regulation required for de-loading
Whenever possible, the breakers are de-loaded before they are opened, to reduce the wear on them. A breaker is de-loaded by
reducing the flow of power through the breaker to the required level. In AUTO and SEMI mode, the power management system de-
loads a breaker by regulating and/or starting the appropriate gensets to take the load off that breaker.
INFO
The power management system does not normally disconnect loads to de-load breakers. A load is only disconnected if the
conditions for a non-essential load (NEL) trip are met.
Regulation
For de-loading, the controller must be able to adjust the genset frequency (by regulating the genset governor).
De-loading uses the same principles as synchronisation. For synchronisation, the power management system adjusts the genset
speed(s) so that the frequencies and phases of the power sources on either side of the breaker match. For de-loading, the power
management system adjusts the genset speed(s) to minimise the flow of power through the breaker.
The power management system (PMS) can only regulate the voltage and frequency of the gensets, by using the GENSET
controllers. The PMS cannot regulate the voltage or frequency of the shaft generator, the shore connection, or (in some cases) the
busbar. Where the PMS must de-load equipment that is not regulated, the PMS therefore regulates the gensets to de-load to the
unregulated equipment.
Genset breaker de-loading in SEMI mode
The controller only responds to operator and external breaker commands in SEMI mode.
If the operator pushes the push-button
Open breaker
on the display unit of a GENSET controller in SEMI mode, the power
management system checks whether opening the breaker would cause a blackout. If it would, the power management system will
not allow the breaker to open.
PMS-controlled stop
If a running genset has a
PMS-controlled stop
alarm action, the power management system will start the next genset, synchronise it
with the busbar, and close its breaker. The power management system will then de-load and open the genset breaker, and stop the
genset that had the
PMS-controlled stop
alarm action.
INFO
PMS-controlled stop
does
not
ensure that the genset stops.
PMS-controlled stop
tries to stop the genset, but will not stop a
genset that cannot be de-loaded.
5.2 Synchronisation in each control mode
5.2.1 Synchronisation in AUTO mode
In AUTO mode, the power management system automatically does the regulation required for synchronisation. When the power
sources are synchronised, the controller automatically closes the breaker.
5.2.2 Synchronisation in SEMI mode
In SEMI mode, the controller must receive an external signal to synchronise and close the breaker. The power management system
then automatically regulates the gensets as required for synchronisation. When the power sources are synchronised, the controller
automatically closes the breaker.
Synchronisation in SEMI mode example
The operator presses
Close breaker
on the display unit.
DESIGNER'S HANDBOOK 4189340911K UK
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