
DCA600SSV4F3PB 60 HZ GENERATOR • OPERATION MANUAL — REV. #1 (10/21/22) — PAGE 17
GENERAL PARALLELING INFORMATION
PARALLELING
Paralleling is the sharing of a load between two generator
sets or more.
LOAD SHARING
Load sharing is defined as the proportional division of the
kW and kVAR total load between multiple generator sets
in a paralleled system.
Load sharing is essential to avoid overloading and stability
problems on the system’s generator sets.
ACTIVE POWER (KW) LOAD SHARING
When generator sets operate in parallel, the engine speed
governor of each generator set determines the proportional
sharing of the total active power requirements (kW) of the
system.
The kW load sharing is achieved by increasing or decreasing
fuel to the system’s engines. As the fuel to the engine of
one generator set in a group is increased, it will not lead to
an increase in speed and hence frequency (as it would if it
were operating alone), but it will lead to an increase in the
proportion of the total kW load that it will deliver.
As the fuel to the engine of one generator set in a group
is decreased, it will not lead to a decrease in speed and
hence frequency (as it would if it were operating alone),
but it will lead to a decrease in the proportion of the total
kW load that it will deliver.
The control system of the generator sets (via the engine
speed control system) monitors and controls the sharing
of the total kW load in proportion to the relative rating of
the engines on the system’s generator sets.
REACTIVE POWER (KVAR) LOAD SHARING
When generator sets operate in parallel the alternator
field excitation system of each generator set controls
the proportional sharing of the total reactive power
requirements (kVAR) of the system.
The kVAR load sharing is achieved by increasing or
decreasing the field excitation to the system’s alternators.
As the field excitation of one generator set in a group is
increased (i.e. over excited), it will not lead to an increase
in voltage (as it would if it were operating alone), but it will
lead to an increase in the proportion of the total kVAR load
it will deliver and a decrease in its power factor.
As the field excitation of one generator set in a group is
decreased (i.e. over excited), it will not lead to a decrease
in voltage (as it would if it were operating alone), but it will
lead to a decrease in the proportion of the total kVAR load
it will deliver and an increase in its power factor.
An undesirable circulating reactive current (cross current)
will flow in the system if the excitation of the alternators is
not matched.
LOAD MANAGEMENT
These generators are set up to automatically manage load
based on demand. Load management is only functional in
Auto mode. While in Auto mode, if the auto-start contacts
are closed, load management is active by default. Load
management will only run the number of units needed to
support the load.
If the load demand is small, only one generator will remain
running while the other generators will remain in Standby
mode. If the load increases above 80% of its capacity, it
will start the next generator. The next generator priority is
based on the time remaining on the maintenance timer.
Generators with more time until scheduled maintenance will
take priority over units that are almost due for maintenance.
Once the second unit starts, it will synchronize and parallel
in, then ramp up to share the load. If the load levels drop
below 35% of its combined rating, the generator that is
no longer needed will ramp off, shut down, and wait in
Standby mode.
SEQUENCING
These generators are capable of sequencing for control
of balanced maintenance schedules. As described above,
these generators can start and stop as demand raises or
lowers. In addition, if a unit gets to the point of maintenance,
it will ramp off and start the next generator to relieve it based
on the time remaining on the maintenance timer.
After maintenance is performed, the maintenance timers
should be reset to the recommended service interval. This
is usually 250 hours depending on the engine oil type.
NOTICE
Ethernet communication is required when the
generators are configured for the sequencing mode
of operation.