Mps Transfer Switches - Generac Power Systems PowerManager 004975-2 Manual

Figure 3.21 — Regular Settings
In the lower left corner of the "Regulator Settings Page" is a sec-
tion called "Backup Paralleling Options". Enable the "Automatic
with PLS" setting (Figure 3.22).
Figure 3.22 — Automatic with PLS
Close this window and drill down to each generator PM-PC and
repeat this operation on each PM-PC. If the PM-PC(s) and the
PM-SC are not set up the same, power will not be shared correctly
while operating in backup mode.
Procedure for Entering Automatic Backup Mode:
The following procedure refers to generator numbers. The genera-
tor number is the ModBus address of that generator. Backup mode
priorities and delays are based on the generator numbers. Also, the
wiring is specified based on the generator number. Therefore, the
generators should be numbered sequentially via GenLink starting
at #1.
The MPS will normally have all PM-SC and PM-PC key switches
in the AUTO position. If the PM-SC or any PM-PC is no longer
communicating with the MPS, an alarm will sound on the PM-SC,
PM-PC, or both. If the utility power is lost at this time, the MPS
will automatically enter the backup mode. In the automatic backup
mode, the PM-SC continues to control as much of the system as
it can. However, the PM-PC(s) that are no longer under the PM-SC
control will start on their own per the following procedure.
When the utility fails, the ATS(s) activate the remote start signal.
The remote start signal is connected to all generator PM-PC(s) as
well as the PM-SC.
The generators will all start and warm up. Only generators #1
and #2 are able to connect to a dead Bus, so they will connect
to the Bus when they are ready for load. The link between the two
generators prevents them from both connecting at the same time.
As each generator connects, it indicates to the PM-PLS that it has
done so.
The remaining generators synchronize and connect to the Bus as
they become ready for load. As each generator connects, it indi-
cates to the PM-PLS that it has done so.
Depending on the PM-PLS programming, it will determine how
much power is available and what the maximum power needs
are. If there is enough power available for a given permissive to
be active, the PM-PLS will activate the appropriate permissive
signals.
If a generator should shutdown the PM-PLS will activate the
appropriate load shed signals to allow the remaining system to
function.
Procedure for Exiting Automatic Backup Mode:
If the MPS is operating in automatic backup mode, the ATS(s) will
need to transfer back to utility before exiting this mode.
When the utility returns, the ATS(s) should automatically switch
back to the utility and deactivate the remote start signal. This
will cause all the generators to disconnect from the Bus, enter
cooldown, and then shutdown.
When the system is able to return to normal operation, it will do so
only after the remote start signal to the PM-SC/PM-PC(s) deacti-
vates and all the generators have shutdown.
An MPS will perform better in backup mode with like-sized
generators than with unlike-sized generators.

3.12 MPS TRANSFER SWITCHES

The PM-SC can be set up to control separate multiple transfer
switches, these can be either the manufacturer's own commu-
nications enabled switches (MTS), standalone transfer switches
(GTS), or third party switches. The PM-SC can also be used
with a SINGLE Soft Load Transfer Switch (STS). Up to eight MTS
switches can be connected to a PM-SC. For third party or GTS
switches there are three groups of settings for permissive and
load shed relays plus a critical load setting. These relays can be
connected to multiple transfer switches as required.
The PM-SC is designed to work with the manufacturer's genera-
tor sets that have paralleling capability (designated PM-PC). The
transfer switches supplying the equipment (non-critical) load are
provided with input signals for start permissive and trip to neutral.
This allows for flexible system startup and load shedding capabili-
ties. The overall system is known as the Modular Power System
(MPS). The PM-SC can control generator sets with different power
ratings, and various rating transfer switches may be used to allow
system flexibility. A real time clock and calendar is included so the
user can program the PM-SC to exercise the system as required.
Operation
NOTE:
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