6.8 Parallel to mains operation – MINT
MINT only
If the MCB is closed (MCB feedback is present) and the gen-set has been synchronized to the bus
bar, the parallel to mains operation will follow. It consists of the following phases:
6.8.1 Ramping the power up
The first phase of the PTM operation is the ramping of the gen-set up to the desired power level
derived from the system baseload or up to the load given by load sharing with other gen-sets
connected to the bus bar. The speed of the ramp is given by the setpoint Load Ramp. The setpoint
adjusts the ramp time for a change from 0% to 100% of nominal power.
6.8.2 Load control modes
There are two load control modes – system baseload and load sharing – which are selected by the
setpoint #SysLdCtrl PtM. See the setpoint description for more information. If system baseload mode
is selected, the Load regulation loop is active to maintain the load at the requested level which is
derived from the system baseload. Each running gen-set takes a relatively equal part of the system
baseload.
In load sharing mode, the loop LS (load sharing) is active to maintain the load at the same relative
level as the other loaded gen-sets in the group. The behaviour in this case is identical to multiple
island mode.
NOTE:
The process of determining which gen-sets shall run is described in the power management chapter.
6.8.3 Power factor control
In system baseload mode the power factor is regulated to a constant value given by the setpoint
#SysPwrFactor. The PF regulation loop is active. In load sharing mode, also power factor sharing is
active to keep the power factor of all loaded gen-sets at an equal level. Regulation adjustment
setpoints are available in the Volt/PF control group.
6.8.4 Ramping the power down
When a stop command is received – e.g. power management or binary input Sys Start/Stop is
deactivated or the STOP button is pressed – the gen-set load is ramped down before opening the
GCB. The ramp speed is given by the setpoint Load Ramp, the end level is given by GCB Open Level
and the timeout for finishing the ramping without reaching the open level is given by GCB Open Del.
When the GCB button is pressed, the gen-set load is ramped down before opening the GCB as well.
But after the GCB has been opened, the gen-set remains running until a stop command comes or the
GCB is pressed again to reclose the GCB.
Continue to the cool down and stop phase.
6.9 Island operation – SPtM
SPtM only
A situation where the MCB is open and the load is supplied from the gen-set is called Island operation.
This situation will occur in the following cases:
1. The GCB has been closed to a dead bus bar, or
2. The gen-set was running parallel to the mains and the MCB has been opened.
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