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EQUIPMENT DESCRIPTION
The Modular Power System (MPS) consists of multiple alternating
generator sets designed to deliver electrical power to compatible
electrical loads when the UTILITY power supply is not available or
has dropped to an unacceptable level. The MPS system contains
multiple genset modules controlled by the PowerManager™
System Control (PM-SC) to provide a single source of output
power. The PowerManager™ contains three levels of load shed
relays which allows the system to continue to deliver power even
if some of the generator sets are out of service. The MPS system
consists of at least two generator sets, each controlled by its own
on-board controller (PM-PC). The PowerManager™ communi-
cates with these individual controllers (PM-PC) to synchronize and
parallel multiple generators together. The PowerManager™ receives
a loss of utility power signal and through RS-485 communications,
starts the generators, parallels them together, signals the external
transfer switch(es), and divides the load proportionally between
the generators.
This manual contains information related to the individual genset
modules and their control systems but does not contain detailed
information about the external transfer switch nor the
PowerManager™ control system. For more detail about the overall
control system refer to the PowerManager™ PM-SC manual, part
number 0J6851.
The Modular Power System is connected together under the con-
trol of a single PowerManager™ controller to build larger capacity
systems (up to 15 individual generator sets working together).
Employing open (OTTS) or closed (CTTS) external transfer switch-
es, these systems can be monitored and controlled via the
GenLink™™ software product. GenLink™™ allows an operator to
monitor operations, examine operating conditions, set parameters
and record alarm activity.
SEQUENCE OF OPERATION
There are a variety of terms and techniques that are used in the
paralleling of generators, some will be discussed in the following
section.
In a typical standby system, a power outage will be sensed by a
transfer switch. A time delay is usually incorporated in this signal in
order to prevent nuisance tripping of the power system. After the
time delay has been met, the transfer equipment will send a start
signal to the generator. Once the generator is up to speed and it's
voltage and frequency are stable, the transfer switch will automati-
cally disconnect from the utility bus and transfer the load to the
generator (emergency) bus. When the utility supply returns, the
load is transferred back to the utility bus after a pre-set user select-
able time. The generator(s) will then begin a "cool-down" cycle and
shutdown.
The MPS system utilizes the same concept, but a few additional
steps are needed in order to parallel the generators. The following
example is of a two-generator MPS application.
When an outage occurs, the generators within the system will
receive a start signal from the PowerManager™. The first genera-
tor to reach its rated voltage and frequency will close it's contactor
onto the "dead" generator bus. The synchronizing function in the
PM-PC controls will begin driving the second engine generator into
synchronization. Once the generators are synchronized, a signal
will be sent to close the contactor of the second generator.
Now that the generators are paralleled, a signal is sent to the
PowerManager™ indicating the generators are ready to accept
load. The load is then transferred to the generator bus. When the
utility power returns, the PowerManager™ returns the transfer
switch(es) to the utility position. Both contactors on the generators
open and the generators begin a "cool-down" cycle then shut-
down.
ENGINE PROTECTIVE DEVICES
The standby generator may be required to operate for long
periods of time without an operator on hand to monitor such
engine conditions as coolant temperature, oil pressure or rpm.
For that reason, the engine has several devices designed to
protect it against potentially damaging conditions by automati-
cally shutting down the unit when the oil pressure is too low, the
coolant temperature is too high, the coolant level is too low, or
the engine is running too fast.
NOTE:
Engine protective switches and sensors are mentioned here for
the reader's convenience. Refer to the control panel paragraphs
for additional automatic engine shutdown information.
COOLANT TEMPERATURE SENSOR
The coolant temperature is monitored by the control system. If
coolant temperature rises above a safe, preset level the control
system automatically shuts down the engine.
LOW COOLANT LEVEL SENSOR
If the engine coolant level drops below a safe level, it is possible
for the engine to overheat without automatic shutdown. To prevent
such overheating, the engine has a low coolant level sensor. If the
level of engine coolant drops below the level of the low coolant
level sensor, the control system automatically shuts down the
engine.
OIL PRESSURE SENSOR
The control system monitors engine oil pressure during operation.
If oil pressure drops below a safe level, the system automatically
shuts down the engine.
OVERSPEED SHUTDOWN
The control system monitors engine speed during engine cranking,
start-up, operation and shutdown. Engine speed signals are deliv-
ered to the control system whenever the unit is running. If the
engine speed exceeds a safe, preset value, the system automati-
cally shuts down the engine.
General Information
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