Neither voltage nor a frequency regulation loop is active. Keeping voltage and frequency at rated
values is the task of AVR and the governor.
When a stop command is received – e.g. the binary input Sys Start/Stop is deactivated or the STOP
button is pressed – the GCB will be opened and the gen-set will go to cool down phase.
NOTE:
When using the GCB button in MAN mode, the gen-set will not go to cool down and stop.
6.9.1 Island to PtM transfers
SPtM only
If the mains are OK, the gen-set can be transferred back to the parallel to mains operation. The
transfer can be done as no-break transfer (Reverse synchronizing) or break transfer (Changeover).
Which of these kinds will be performed depends on the binary input RevSyncDisable.
In AUT mode or TEST mode with automatic return, the reverse synchronizing or changeover is started
automatically after the mains have been restored and remain healthy for a period given by the setpoint
MainsReturnDel. Reverse synchronizing can be started manually by pressing MCB button in MAN
mode.
Reverse synchronizing
The reverse synchronizing process is identical to Forward synchronizing, but MCB is closed instead of
GCB. In the event that the reverse synchronizing is not successful, RevSyncTimeout alarm is issued
and the gen-set continues in island operation. After the alarm has been reset, the gen-set can try to
perform reverse synchronizing again.
Changeover
The changeover is performed if the reverse synchronizing is disabled with the RevSyncDisable binary
input.
The GCB is opened first and after a time period of Transfer Del the MCB is closed.
6.10 Island operation – MINT
MINT only
This chapter describes the situation where multiple gen-sets are running parallel to each other but not
with mains. This situation will occur either when:
1. The common bus bar is dead due to opened MCB or there are no mains at all and the group
of gen-sets has been activated, or
2. The group was running parallel to mains and the MCB has been opened.
NOTE:
The controller in MINT application does not control the MCB! Only the MCB position is evaluated from
the binary input MCB Feedback and the position is the basic source of information for switching
between island and parallel to mains operation.
If the bus bar is empty, the first gen-set will close its GCB without synchronizing. Following gen-sets
will synchronize to the already energized bus bar. In the event that multiple gen-sets start
simultaneously and the bus bar is empty, the system will prevent closing of multiple GCBs to the bus
bar without synchronizing. Instead of this, one of the gen-sets will close the GCB and energize the bus
bar and the others will wait and then synchronize to the bus bar.
When a stop command is received, e.g. from the power management or binary input Sys Start/Stop is
deactivated or the STOP button is pressed, the GCB will be opened and the gen-set will go to cool
down phase.
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